Electricity Portfolio Standards: Background,
October 21, 2020
Design Elements, and Policy Considerations
Ashley J. Lawson
Electricity portfolio standards, such as renewable portfolio standards and clean energy standards,
Analyst in Energy Policy
are policies aimed at changing the energy sources used to generate electricity. Supporters identify

multiple policy goals, including greenhouse gas reduction, technology innovation, and job
creation. Twenty-nine states, three U.S. territories, and the District of Columbia are currently

implementing mandatory portfolio standards. Congress, to date, has not established a national
portfolio standard, though bills that would do so have been introduced in every Congress since the 105th.
Congressional interest in 2011 and 2012 prompted a variety of analyses about potential impacts of a national portfolio
standard. The national electricity generation profile has changed since then in ways that might make previous analyses less
relevant to any future policy debate. Between 2012 and 2019, in the U.S. generation from coal fell (from 37% to 23%),
generation from natural gas increased (from 30% to 38%), and generation from renewable sources (e.g., hydropower, wind,
solar) increased (from 12% to 18%). Many expect these trends to continue, regardless of any new federal policy related to the
electric power sector.
Portfolio standards are generally envisioned as market-based policies in the sense that they use financial incentives rather
than prohibitions to achieve policy goals. Several key concepts in portfolio standards are common to other market-based
policies. Credits are an accounting mechanism used for compliance and are tracked in electronic databases sometimes called
registries. Lawmakers can choose the degree of flexibility around credit use in a portfolio standard, with potential impacts on
overall policy costs and benefits. Procedures to monitor, report, and verify credits can help portfolio standards achieve their
policy goals and reduce the risk of fraud.
Other concepts are specific to portfolio standards. Choices about these design elements can strongly influence policy
outcomes. Generally, choices that would tend to reduce costs would also tend to result in fewer changes in the electricity
generation profile.
The choice of which energy sources would be eligible for compliance, and therefore would be incentivized by the program, is
often central to policy discussions about portfolio standards. Past proposals have included a range of eligible sources,
including renewable sources, nuclear, fossil fuel-fired power plants equipped with carbon capture and sequestration
technology (CCS), and natural gas combined cycle power plants. Some proposals have included nongenerating sources like
energy storage and energy efficiency as well. Other design elements include whether all utilities should have to comply with
a portfolio standard or whether some would be exempted; how much generation from eligible sources a portfolio standard is
designed to achieve; by when should the desired amount of generation from those sources be achieved; to what share of a
utility’s electricity sales should a portfolio standard apply; and whether any provisions should be included that delay or halt
compliance under certain circumstances (e.g., undesirably high prices).
If established, a national portfolio standard would likely have economic effects, though estimating these in advance is subject
to some uncertainty. Any sources and associated industries excluded from the definition of eligible sources would likely
experience negative economic effects. At the same time, industries associated with sources included in the standard would
likely experience positive economic effects. The net effect on national economic activity would depend on the design details
of any portfolio standard and the ways that consumers might respond to potentially higher electricity prices.
A national portfolio standard might also have environmental effects compared to a business-as-usual scenario, depending on
design choices such as source eligibility and the change from business as usual a portfolio standard is designed to achieve.
Potential eligible sources vary in their GHG and air pollutant emissions, as well as other attributes such as water consumption
and power density (which can affect land requirements). Implementation could affect environmental outcomes too. For
example, deploying small-scale distributed eligible sources might have different effects than deploying large-scale eligible
sources.
Another policy consideration is potential interaction with state energy policies like existing portfolio standards, electricity
infrastructure siting, and the use of competitive markets to influence electricity investment decisions. Such interactions may
generate debate regarding preemption and highlight potential federalism concerns.
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Contents
Introduction ..................................................................................................................................... 1
U.S. Electricity Generation Profile .................................................................................................. 1
Key Portfolio Standard Concepts .................................................................................................... 3
Portfolio Standard Design Elements ............................................................................................... 7
Source Eligibility ...................................................................................................................... 7
Utility Applicability .................................................................................................................. 9
Target and Stringency .............................................................................................................. 12
Base Quantity of Electricity .................................................................................................... 14
Cost Containment Mechanisms ............................................................................................... 15
Selected Policy Considerations ..................................................................................................... 16
Potential Economic Effects ..................................................................................................... 17
Potential Environmental Effects .............................................................................................. 18
Interaction with State Portfolio Standards .............................................................................. 18
Interaction with Other State Energy Policies .......................................................................... 20

Figures
Figure 1. Total National Electricity Generation by Source, 2012-2019 .......................................... 2
Figure 2. Share of U.S. Distribution Utilities for Selected Size Ranges ........................................ 11
Figure 3. U.S. Electricity Sales by Distribution Utility Size ......................................................... 12
Figure 4. Examples of Conceptual Approaches to Phasing in Targets .......................................... 13

Tables
Table 1. Count of U.S. Distribution Utilities for Selected Size Ranges ......................................... 11

Table A-1. Renewable Portfolio Standard and Clean Energy Standard Bills from the 105th
Through 116th Congresses .......................................................................................................... 22

Appendixes
Appendix. Legislative Proposals in the 105th-116th Congresses .................................................... 21

Contacts
Author Information ........................................................................................................................ 32

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Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations

Introduction
Legislative proposals have been introduced since the 105th Congress to create a national
electricity portfolio standard that would require electric utilities to procure a certain share of the
electricity they sell from specified sources. Thirty states, three U.S. territories, and the District of
Columbia are currently implementing mandatory portfolio standards, and an additional eight
states and one territory have voluntary versions.1
Various existing and proposed portfolio standards use a range of terms for similar concepts. A
renewable portfolio standard (RPS) typically means a requirement to procure electricity from
renewable sources. A clean energy standard (CES) typically means a variant of an RPS that
includes some nonrenewable sources, such as nuclear or selected fossil fuels, in the requirement.
Some lawmakers and stakeholders use these terms interchangeably, and some use the term CES
or “clean energy” to refer only to renewable sources. This report uses the more general term
“portfolio standard” to avoid confusion between RPS and CES.
At both the federal and state level, lawmakers express multiple goals for portfolio standards.
These include greenhouse gas reduction, technology innovation, and job creation. Policy design
choices, as discussed in this report, can influence the extent to which portfolio standards might
achieve those or other goals.
Other policies could potentially achieve the same goals as portfolio standards. For example, tax
incentives or funding for technology research, development, and deployment could promote the
use of certain types of electricity generation sources by reducing their costs. This report does not
compare portfolio standards with other policy options, nor does it fully examine the costs and
benefits of establishing a national portfolio standard compared to business-as-usual trends in the
electric power sector.
This report provides background on portfolio standards and an overview of policy design
elements to inform potential congressional debate of a national portfolio standard, building on
previous CRS reports addressing this topic.2 This report also analyzes potential effects of
portfolio standard design choices, with an emphasis on economic effects, environmental effects,
and potential interactions with state energy policies. Other potential effects that may be of
congressional interest, but are outside the scope of this report, include public health,
considerations regarding critical minerals used in some energy sources, electric reliability,
cybersecurity, and geopolitics.
U.S. Electricity Generation Profile
A number of government agencies, nongovernmental organizations, academic researchers, and
private sector entities analyzed potential effects of a national portfolio standard in 2011 and 2012

1 DSIRE, Renewable and Clean Energy Standards, September 2020, https://s3.amazonaws.com/ncsolarcen-prod/wp-
content/uploads/2020/09/RPS-CES-Sept2020.pdf. Texas and Iowa have portfolio standards that set a requirement in
terms of installed capacity, not share of sales. The federal bills introduced since 2005 that would have established a
national portfolio standard did not take this approach, so the discussion in this report applies to targets implemented as
a share of total electricity sales.
2 CRS Report R41493, Options for a Federal Renewable Electricity Standard, by Richard J. Campbell, and CRS
Report R41720, Clean Energy Standard: Design Elements, State Baseline Compliance and Policy Considerations, by
Phillip Brown.
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because of congressional interest at that time.3 Since 2012, the U.S. electric power sector has seen
several changes in its generation profile that were unanticipated in those analyses. These include
an increase in generation from sources using natural gas and renewable energy, along with a
decrease in coal-fired generation. The current U.S. electricity generation profile and market trends
may be important context for any congressional debate about a potential national portfolio
standard.
The U.S. Energy Information Administration (EIA) reports that total electricity generation was
4,047,766 gigawatt-hours (GWh) in 2012 and 4,153,092 GWh in 2019, an increase of 3%.4
Figure 1. Total National Electricity Generation by Source, 2012-2019

Source: EIA, Electricity Data Browser, https://www.eia.gov/electricity/data/browser/.
Notes: Renewables = utility scale and small-scale solar, wind, wood and wood-derived fuels, landfil gas, biogenic
municipal solid waste, other waste biomass, geothermal, and hydroelectric facilities. Other = petroleum liquids,
petroleum coke, other gas, nonbiogenic municipal solid waste, and other miscellaneous energy sources. EIA did
not report data for small-scale solar in 2012 or 2013. In 2014, small-scale solar accounted for 0.3% of total U.S.
electricity generation.
Between 2012 and 2019, the share of electricity generation from different sources has changed.
Coal generated 37% of total generation in 2012 and 23% in 2019. Natural gas generated 30% of
total generation in 2012 and 38% in 2019. Renewable sources, including hydropower, wind, solar,
geothermal, and biomass, generated 12% of total generation in 2012 and 18% in 2019. Many
expect these trends to continue. For example, EIA’s projection of current laws, regulations, and
market trends show coal contributing 13% of total generation in 2050, natural gas contributing
36%, and renewable sources contributing 38%.5

3 See, for example, presentations from a 2011 workshop held jointly by the nonprofit organization Resources for the
Future and the U.S. Environmental Protection Agency, A Federal Clean Energy Standard: Understanding Important
Policy Elements
, https://www.rff.org/events/all-events/a-federal-clean-energy-standard-understanding-important-
policy-elements/.
4 EIA began collecting data on small-scale generation from solar photovoltaic facilities in 2014. This report includes
small-scale generation data when they are available in order to provide the best available estimate of total generation in
all years. This may complicate comparisons between years. EIA reports generation from small-scale solar photovoltaic
facilities in 2014 was 11,233 GWh, or 0.3% of total U.S. electricity generation in that year.
5 EIA, Annual Energy Outlook 2020, Table 8. Electricity Supply, Disposition, Prices, and Emissions, January 29, 2020,
https://www.eia.gov/outlooks/aeo/.
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Electric power sector observers generally agree on the factors causing these trends, although the
relative importance of each factor is subject to some debate. The changes from 2012 to 2019 are
due to a combination of (1) continued low natural gas prices and low wholesale electricity prices;
(2) federal environmental regulations, especially on coal-fired power plants; (3) declining capital
costs for wind and solar sources; (4) federal tax incentives for wind and solar sources; (5) state
portfolio standards and other policies; (6) changing consumer preferences, especially large
corporations’ and institutions’ commitments to procure more electricity from renewable sources;
and (7) natural turnover as generators age.6
Differing perspectives over the relative influence of these factors could affect stakeholder views
on the merits of a federal policy to promote greater use of certain energy sources for electricity
generation. Some might argue that sources that are now cost competitive (e.g., natural gas, wind)
may not require policy support to increase their share of the electricity generation profile. Others
may see electricity generation as solely an area for state policy as discussed further in the section
“Interaction with Other State Energy Policies,” below. A related consideration may be whether
increasing the pace of change in the U.S. electricity portfolio could pose reliability risks.7
Key Portfolio Standard Concepts
Key concepts in portfolio standard policymaking may or may not have identical meaning when
used in other contexts. For convenience and clarity, this section introduces key concepts used in
this report.
As noted above, lawmakers and observers are not consistent in their use of terms related to
portfolio standards. Renewable portfolio standard (RPS) is the most frequently used term to
describe a portfolio standard, though renewable energy standard, alternative energy portfolio
standard, and others are in use.8 The term clean energy standard (CES) is frequently used to refer
to a variant of RPS in which certain nonrenewable sources are eligible in addition to renewable
sources, but some federal legislative proposals have used the term “clean energy” to refer only to
renewable sources.9 The Appendix provides more information about previously introduced bills.
Banking refers to the extent to which credits issued in the program may be used for compliance
after their vintage year (see definition, below). Banking provisions can equivalently be described
in terms of expiration. For example, if credits expire after two years, then banking for two years is
allowed. A related concept is borrowing which allows credits of future vintage years to be used
for compliance.

6 See DOE, Staff Report to the Secretary on Electricity Markets and Reliability, August 2017, https://www.energy.gov/
sites/prod/files/2017/08/f36/Staff%20Report%20on%20Electricity%20Markets%20and%20Reliability_0.pdf, and
Galen Barbose, U.S. Renewable Portfolio Standards 2019 Annual Status Report, Lawrence Berkeley National
Laboratory, July 2019, https://emp.lbl.gov/publications/us-renewables-portfolio-standards-2.
7 For a discussion of potential reliability risks associated with wind and solar sources, see CRS Report R45764,
Maintaining Electric Reliability with Wind and Solar Sources: Background and Issues for Congress, by Ashley J.
Lawson.
8 A compilation by the National Conference of State Legislatures (NCSL) shows this variability. NCSL, State
Renewable Portfolio Standards and Goals
, updated April 17, 2020, http://www.ncsl.org/research/energy/renewable-
portfolio-standards.aspx.
9 Treatment of hydropower is an exception. Many state RPSs exclude generation from large, existing projects (e.g.,
large dams) but include small, new projects, so those state RPS definitions of “renewable” sources have size or age
restrictions for hydropower. Some state and federal CES proposals would include large, existing hydropower as a “non-
renewable” source.
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Base quantity of electricity is the sales volume to which the portfolio standard applies. The base
quantity could equal total electricity sales, but it need not. Excluding sources from the calculation
of the base quantity changes the required amount of generation from eligible sources in absolute
terms. The base quantity to which the portfolio standard applies also affects the financial
incentive that different sources receive. Even sources deemed ineligible under the portfolio
standard could receive some policy support if they were excluded from the base quantity of
electricity. This concept is discussed further in the section “Base Quantity of Electricity.”
Carve outs, tiers, multipliers, partial crediting, and usage limits are all policy options for
influencing the relative support that different types of eligible sources receive under a portfolio
standard. Eligible sources will be available at different costs. Policymakers may want to avoid a
situation where compliance is achieved mostly through the use of a single, low-cost source. A
carve out is a requirement within the overall policy requirement to achieve a minimum level of
compliance by using a certain source. Carve outs have been used, for example, to require use of
solar energy even when that was more expensive than other eligible sources. The same goal might
be accomplished through use of tiers. Typically, a carve out will apply to a single source type
while a tier might apply to multiple source types. A related concept is that of usage limits that set
maximum levels for compliance from certain sources. Multipliers are rules under which selected
sources receive more than the usual amount of credit for generating electricity, but the credits are
completely fungible (see definition, below) with others. Sources that are eligible for multipliers
would receive extra policy support, relative to other sources. Multipliers could be used, for
example, to encourage demonstration and commercialization of new technologies. Partial
crediting
would give selected sources less than the usual amount of credit and could be applied to
sources lawmakers wanted to give less policy support.
Clean energy, as used in this report, refers to the set of sources that lawmakers might choose to
include in a portfolio standard. These sources could include wind, solar, geothermal, biomass,
hydropower, marine energy, nuclear, natural gas combined cycle generators, or fossil fuel-fired
generators equipped with carbon capture and sequestration technology (herein, CCS). Lawmakers
could also choose to include nongenerating sources such as energy storage or energy efficiency.
Other considerations about the choice of eligible sources are discussed in the section “Source
Eligibility.”

Covered entities are the entities with a compliance obligation under a portfolio standard. Most
portfolio standards being implemented by states or proposed at the federal level have electricity
distribution utilities as the covered entities. These utilities may or may not own electricity
generators, depending on state and local regulatory regimes.10 Typically, a utility procures
electricity from a number of different generators using a variety of energy sources (its portfolio).
Other considerations about the choice of covered entities are discussed in the section “Utility
Applicability.”

Credits are the unit of accounting for portfolio standards and other market-based policies.
Electricity cannot easily be traced from its point of generation to its point of consumption, so
accounting measures are required to assess compliance with a portfolio standard. In many
existing portfolio standards, credits are issued by an administrator to a generator that uses a clean
energy source.11 The number of credits issued is based on actual measured electricity generation

10 These are described in DOE, United States Electricity Industry Primer, July 2015, https://www.energy.gov/sites/
prod/files/2015/12/f28/united-states-electricity-industry-primer.pdf.
11 Past federal proposals have differed in their choice of administrator of a national portfolio standard. Proposals have
included the Department of Energy, the U.S. Environmental Protection Agency, and the Federal Energy Regulatory
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Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations

(i.e., ex post).12 The generator can then sell credits to a utility, and the utility surrenders them to
the program administrator to demonstrate compliance. If a generator sells both electricity and
associated credits to the same entity, the credit is bundled. If a generator sells electricity and
associated credits to different entities, the credit is unbundled. Lawmakers could allow entities
other than generators and utilities (e.g., financial institutions) to buy and sell credits, or they could
allow only utilities with a compliance obligation to purchase credits. The price that utilities would
pay for credits would depend on the portfolio standard stringency, the overall volume of
electricity generated by clean energy sources, and other market factors. The sale of credits could
create an additional source of revenue for a generator, potentially improving its economic
performance relative to a business-as-usual scenario with no portfolio standard. In some cases,
the ability to sell credits might be the deciding factor for whether a new generator would be
constructed (or, for existing generators, whether a generator would remain operational instead of
being retired). In other cases, generators may be profitable without the sale of credits, and the
credits might create a windfall profit.13 The requirement to buy credits would likely increase the
overall costs for a utility. Typically, a utility’s costs for complying with a portfolio standard would
be passed on to its customers.14 If a utility were unable to fully pass on its compliance costs, it
might see reduced profitability.
Fungibility is the attribute of credits allowing them to be used interchangeably and without
penalty. Since many state portfolio standards already exist, federal policymakers would have to
decide if these state credits would be fungible with federal credits under a federal portfolio
standard. If they were, then current holders of state-issued credits could use them for compliance
with a federal portfolio standard or sell them to another entity for that purpose. If they were not,
then state-issued credits could potentially lose value, depending on the relative stringency of a
national portfolio standard and the state portfolio standard. Some states have implemented cap-
and-trade programs in addition to portfolio standards, both of which aim to reduce greenhouse
gas emissions from the electricity generation. Like portfolio standards, cap-and-trade uses credits
(also called allowances) as an accounting mechanism and for compliance purposes. Under
existing state policies and federal proposals, credits under portfolio standards are not fungible
with allowances under cap-and-trade programs for greenhouse gases.15
Market-based policies attempt to use financial incentives to achieve policy goals. Many
discussions contrast them with command-and-control policies that set specific permissions or
prohibitions.16 Portfolio standards indirectly provide financial incentives because they create
demand for generation from certain eligible sources in electricity markets, even if those eligible
sources are more expensive than ineligible sources. Some observers argue this mechanism is a

Commission.
12 Ex post, or “after the fact” measurements, are in contrast to ex ante or “beforehand” estimates.
13 Windfall profits are those that a company earns as a result of circumstances outside its control and unrelated to its
planning, operations, and investment decisions. Defining what constitutes a windfall profit can be controversial.
14 The mechanism for this cost pass-through would vary according to local and state utility regulation. For example, it
might be passed through as a utility expense or it might be reflected in higher wholesale electricity rates (if clean
energy sources increased wholesale rates).
15 Fungibility between portfolio standards and cap-and-trade programs for greenhouse gases is complicated by the fact
that portfolio standard credits represent a unit of electricity, typically, 1 megawatt-hour (MWh) while allowances in
cap-and-trade programs represent a unit of greenhouse gas emissions, typically 1 ton carbon dioxide (t CO2). Enabling
fungibility between the two might be possible by establishing conversion rules between MWh and t CO2. Whether this
is desirable might depend on expected interactions between the two policies, if both were implemented.
16 Organisation for Economic Co-operation and Development (OECD), Glossary of Statistical Terms, updated
November 2, 2001, https://stats.oecd.org/glossary/detail.asp?ID=383.
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disruption of market forces.17 In comparison, tax credits, grants, and loan guarantees provide
direct financial incentives for eligible sources and therefore lower the cost of those sources in the
market. Most portfolio standard proposals do not expressly prohibit use of ineligible sources, but
they do create a financial disincentive to use them.18
Monitoring, reporting, and verification (MRV) are three distinct steps that ensure that market-
based policies achieve the desired goals. In the case of portfolio standards, MRV practices would
measure the amount of electricity generated by eligible sources and verify that each unit of
electricity from eligible sources was used only once for the purpose of compliance. Monitoring
and reporting electricity generation is commonplace in the industry, at least for large-scale
generators connected to the electricity transmission system.19 Verification for market-based
policies is often completed by an independent third party.
Qualifying facilities (QFs) are established in the Public Utility Regulatory Policies Act of 1978
(P.L. 95-617; PURPA) as certain small power production facilities and cogeneration facilities that
receive special treatment. Utilities must purchase electricity from QFs at a price determined by
what the utility would otherwise have to pay for electricity.20 There is no direct relationship
between QFs under PURPA and sources that would be eligible under a portfolio standard, though
the term “qualifying source” is sometimes used in both contexts. To avoid confusion, this report
refers to sources defined as clean energy under a portfolio standard as “eligible sources.”
Registries, sometimes called tracking systems, are electronic databases used to facilitate credit
issuance and transfer. State portfolio standards typically make use of registries in the following
way. After an administrator verifies the amount of electricity generated from an eligible source,
the administrator creates an appropriate number of credits. These credits are assigned a serial
number and placed in the account of the appropriate entity in the registry. If the credit owner
agrees to sell the credits to another entity, the owner files the necessary documentation with the
administrator, who then authorizes the credits to be transferred to a different account in the
registry. A covered entity would demonstrate compliance by transferring the required number of
credits from its account to the administrator’s account. The administrator would take action to
retire the submitted credits to make sure they cannot be used again for compliance. Cybersecurity
measures can help prevent theft of portfolio standard credits or other fraudulent activity. Some
government agencies currently operate registries that could potentially be used to administer a
national portfolio standard, and some private firms operate registries as well.
Vintage refers to the time period in which a tradeable credit in a market-based policy is issued.
Portfolio standards typically have annual compliance periods, with vintage expressed in years. In
policies with shorter or longer compliance periods, the vintage could be associated with a specific
month or a series of years. For example, if an eligible source generated electricity in the year

17 For example, Stephen Moore and Andrew Vanderplas, State Renewable Energy Mandates: A Regressive Green Tax
on America’s Poor
, The Heritage Foundation, October 30, 2018, https://www.heritage.org/sites/default/files/2018-10/
SR206_0.pdf.
18 The argument that portfolio standards do not create outright prohibitions on ineligible sources might not apply to
proposals that require 100% clean energy. Nonetheless, if alternative compliance payments or other “safety valves”
described later in this report were included, then a portfolio standard would not establish a strict prohibition on
ineligible sources.
19 Small-scale generators connected to the electricity distribution system (e.g., rooftop solar arrays) do not currently
have common monitoring and reporting requirements.
20 Additional discussion of QFs and PURPA is available in Robert E. Burns and Kenneth Rose, PURPA Title II
Compliance Manual
, APPA, EEI, NARUC, and NRECA, March 2014, https://pubs.naruc.org/pub/B5B60741-CD40-
7598-06EC-F63DF7BB12DC.
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2025, it would receive a vintage 2025 credit. The banking and borrowing rules (see definitions,
above) determine the years in which credits of a given vintage may be used for compliance.
Portfolio Standard Design Elements
If Congress chose to establish a national portfolio standard, lawmakers would face choices about
the design of the policy. This section discusses some key design elements and potential effects of
different choices. Often, design choices reflect a balance between increasing the certainty of
achieving policy goals and decreasing the likelihood that consumers will experience undesirable
cost increases. Design elements can interact with each other, so the potential effect of a choice
about one element may be influenced by choices about others.
Not all portfolio standard design choices must be made in legislation. Congress could direct an
agency to promulgate regulations that implement a portfolio standard. The previous federal
proposals summarized in the Appendix take different approaches. Some proposals made very
few design choices and left most decisions to an agency, while others specified most design
choices and left few decisions to an agency. Specifying details in legislation could add
complexity that potentially impedes the legislative process or creates challenges in policy
implementation. On the other hand, specifying details in legislation would give lawmakers greater
control over policy design decisions.
Source Eligibility
Portfolio standards achieve their policy goals by increasing electricity generation from certain
eligible energy sources, as defined by lawmakers. The various energy sources used for electricity
generation have many different attributes that lawmakers might weigh in determining which
sources could be eligible under a national portfolio standard. Recent state policy debates and
many current discussions at the federal level have centered around three attributes: carbon
intensity, technology maturity, and market competitiveness (i.e., cost).21
The debate around carbon intensity has focused on whether to include sources with a carbon
intensity less than conventional coal-fired generators (i.e., low carbon sources), such as natural
gas combined-cycle power plants, or include only those with a carbon intensity of zero (i.e., zero
carbon sources).22 This debate closely relates to the desired environmental outcome of a portfolio
standard. All else being equal, a portfolio standard that includes low carbon sources would likely
result in higher greenhouse gas emissions from the electric power sector than a portfolio standard
under which only zero carbon sources were eligible. Advocates for substantial greenhouse gas
reductions disagree about whether all zero carbon sources should be eligible, with nuclear energy
and CCS being particularly contentious.23 Advocates who support nuclear energy and CCS often

21 Some additional attributes, such as geographic location of eligible sources, have been focus areas in state policy
debates, but may be of less interest in the federal context.
22 Carbon intensity is a measure of greenhouse gas emissions per unit of electricity generated. Carbon intensity is often
expressed as pounds carbon dioxide per megawatt-hour (lbs CO2/MWh) or tons carbon dioxide per megawatt-hour
(t CO2/MWh), as measured at the electricity source. Lifecycle carbon intensities could also be used in determining
source eligibility.
23 See, for example, position statements by Sierra Club at https://www.sierraclub.org/nuclear-free and Niskanen Center
at https://niskanencenter.org/blog/an-open-letter-to-green-new-dealers/.
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present cost arguments, while advocates who oppose those sources often present arguments about
environmental quality and environmental justice.24
The debates around technology maturity and market competitiveness both focus on the desired
balance between supporting new technologies and supporting existing technologies. These
debates closely relate to the desired economic and technological outcomes of a portfolio standard.
Many mature technologies are less expensive than new technologies, so including them as
eligible sources might achieve the policy goals at a lower overall cost.25 Mature technologies may
be easier to deploy, from an operational point of view, since industry best practices and standards
for their use are established. At the same time, a portfolio standard that includes mature
technologies might not encourage the desired level of investment in new technologies. A
compromise may be the use of carve outs, tiers, multipliers, partial crediting, or usage limits, as
described above, to attempt to influence the extent to which covered entities used new or mature
technologies for compliance.26
Energy storage and energy efficiency are not electricity sources, in the usual sense, because they
do not generate electricity. Their supporters argue their deployment helps achieve similar policy
goals as portfolio standards, namely technology innovation, greenhouse gas reduction, and job
creation. Portfolio standards could incentivize energy storage and energy efficiency directly, for
example, by defining them as eligible sources and providing an accounting methodology for
issuing credits to them. Such accounting methodologies may be more complex than those used
for electricity generation, especially for energy efficiency since energy savings cannot be directly
measured.27 Alternatively, portfolio standards could indirectly incentivize deployment of energy
storage or energy efficiency in the setting of the base quantity, as discussed in the section “Base
Quantity of Electricity.”
If lawmakers wanted to incentivize their deployment, another option
could be to establish separate targets for energy storage deployment and energy efficiency
alongside a portfolio standard. Some states with portfolio standards have taken that approach, and
some previous federal proposals took that approach as well.

24 For example, “... relying entirely or predominantly on intermittent resources such as wind and solar significantly
increases the cost and technical difficulty of achieving deep decarbonization.” U.S. Congress, House Committee on
Energy and Commerce, Subcommittee on Environment and Climate Change, Hearing on “We’ll Always Have Paris:
Filling the Leadership Void Caused by Federal Inaction on Climate Change
,” written testimony of Samuel
Thernstrom, CEO Energy Innovation Reform Project, 116th Cong., 1st sess., February 28, 2019, and “we do not support
the use of large-scale biofuel, biomass, mega-hydro dams, nuclear energy, or energy derived from burning waste. They
are usually developed in our backyards, where we live, work, play and pray and they do not reduce emissions at the
source of extraction, only prolonging any real solutions to the climate crisis.” U.S. Congress, House Committee on
Natural Resources, Oversight Hearing on Climate Change: The Impacts and the Need to Act, written testimony of
Elizabeth Yeampierre, Executive Director, UPROSE and co-chair, Climate Justice Alliance, 116th Cong., 1st sess.,
February 6, 2019.
25 Costs for some electricity generation technologies are rapidly changing, so that some newer technologies can be less
expensive than mature technologies. For example, a 2018 analysis from the firm Lazard found that the cost of
generating electricity from new wind and solar projects can, in some cases, be cheaper than generating electricity from
existing power plants using coal or nuclear energy. Lazard, Levelized Cost of Energy and Levelized Cost of Storage
2018
, November 8, 2018, https://www.lazard.com/perspective/levelized-cost-of-energy-and-levelized-cost-of-storage-
2018/.
26 Such policy options are discussed further in Kathryne Cleary, Karen Palmer, and Kevin Rennert, Clean Energy
Standards
, Resources for the Future (RFF), January 24, 2019, https://www.rff.org/publications/issue-briefs/clean-
energy-standards/.
27 Nonetheless, best practices and standards for measuring energy efficiency do exist. For example, State and Local
Energy Efficiency Action Network, Energy Efficiency Program Impact Evaluation Guide, December 2012,
https://www4.eere.energy.gov/seeaction/system/files/documents/emv_ee_program_impact_guide_0.pdf.
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Distributed energy resources (DER) are located near the point of consumption in the electric
power sector (e.g., an individual home, commercial facility, or manufacturing plant). Federal
portfolio standard proposals to date put a compliance obligation on electric utilities; however,
utilities do not always own or operate DER. From the perspective of an electric utility, many DER
are like energy efficiency in that they reduce electricity sales. Some, but not all, DER use
renewable sources, so lawmakers might consider whether to include these as eligible sources.28
The electric power industry does not have established methodologies for measuring generation
from DER, so these would need to be developed if DER were to receive credits. Alternatively, the
setting of base quantities can influence the incentive DERs receive as discussed below.
Other energy source attributes may be of interest to Congress. These include energy density,
which can affect land requirements, and the geographic variability in resource quality. As is also
the case for other topics, geographic variability in natural resources can potentially raise concerns
about uneven wealth impacts in portfolio standard policymaking. For example, the nation’s wind
resources most suitable for wind energy development are concentrated in the central United
States and offshore of the Northeast and Mid-Atlantic.29 The nation’s largest solar resources are
concentrated in the Southwest.30 If eligible sources under a portfolio standard were all
concentrated in one region (or, similarly, if a lack of eligible sources were concentrated in one
region), wealth transfer could occur, raising potential concerns over fairness. Relatedly, some
regions have developed some resources more than others, for example via implementation of state
portfolio standards. Including existing sources, such as those incentivized under state policies,
could potentially result in wealth transfer from states that had not previously implemented
supportive policies. On the other hand, excluding existing sources could be perceived as
penalizing early actors.
Utility Applicability
Most homes, businesses, and other consumers acquire electricity from the electric grid and pay
electric utilities to provide that electricity to them. Over 3,200 electric utilities operate in the
United States, and they are generally classified by three ownership models.31

28 DER come in many forms using different energy sources. Combined heat and power (CHP) facilities using natural
gas and rooftop solar photovoltaic are two common types. Some DER, such as diesel generators, can promote energy
security and resilience by being available during blackouts on the electric grid. DER also potentially lead to overall
efficiencies by avoiding losses associated with transmitting electric power over long distances. On the other hand, they
do not benefit from economies of scale like large central power plants, and they potentially increase risks of
cyberattacks by providing multiple points of entry to the electric grid. Potential disruptions caused by a cyberattack on
distribution networks could be localized or could be geographically widespread, depending on how the attack were
carried out, as discussed in Idaho National Laboratory, Cyber Threat and Vulnerability Analysis of the U.S. Electric
Sector
, August 2016, https://www.energy.gov/sites/prod/files/2017/01/f34/
Cyber%20Threat%20and%20Vulnerability%20Analysis%20of%20the%20U.S.%20Electric%20Sector.pdf. These
attributes may affect the level of support for including DER in any national portfolio standard.
29 The National Renewable Energy Laboratory (NREL) identifies land areas with annual average wind speeds at least
6.5 meters per second and offshore areas with annual average wind speeds at least 7 meters per second as most suitable
for wind energy development. For both types of resources, the relevant wind speed is measured at a height where
turbines might be installed, namely 80 meters for land-based and 90 meters for offshore. More information is available
at NREL, Wind Resource Assessment, https://www.nrel.gov/wind/resource-assessment.html. Although suitable offshore
wind speeds are also found along the Pacific coast, including Hawaii, water depth in these locations might create
technological and cost hurdles for wind energy development that are not experienced along the Atlantic coast.
30 NREL, Solar Maps, https://www.nrel.gov/gis/solar.html.
31 DOE, United States Electricity Industry Primer, July 2015, https://www.energy.gov/sites/prod/files/2015/12/f28/
united-states-electricity-industry-primer.pdf. Other organizations such as irrigation districts and the Tennessee Valley
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 Investor-owned utilities (IOUs) are operated by private companies on a for-profit
basis, and they deliver electricity in at least portions of every state except
Nebraska.32
 Publicly owned utilities (POUs, sometimes municipal utilities or munis) are
owned by local governments and operated on a not-for-profit basis.
 Electric co-operatives (co-ops, sometimes rural co-ops) are member-owned
organizations operated on a not-for-profit basis, typically located in rural areas.
State governments allow IOUs to act as monopolies in their service territory, with no competition
on electricity distribution, in exchange for accepting electricity rates as determined by state
regulators.33 Similar to IOUs, POUs and co-ops are allowed to operate as monopolies with respect
to electricity distribution. Unlike IOUs, they are generally exempt from regulation by state
governments regarding electricity rates, investment decisions, and other operations. POUs and co-
ops together serve about 27% of Americans.34
Lawmakers would have to decide to which type of utility a national portfolio standard would
apply, if they chose to implement such a policy. If one class of utilities, such as co-ops, were
excluded, then the overall effect of the policy might be reduced, since the excluded utilities could
still procure electricity from ineligible sources above the levels set by the portfolio standard. On
the other hand, excluding some utilities based on ownership model might be desirable in order to
address concerns about overall compliance costs and cost distribution. POUs and co-ops often
serve fewer customers than IOUs, so any fixed administrative costs associated with compliance
must be shared by a smaller number of customers, resulting in relatively larger shares of
administrative costs.35 Some state portfolio standards establish different (usually less stringent)
targets for POUs and co-ops, while some exclude them altogether.
Utility size, expressed as annual electricity sales, could be a more precise characteristic than
ownership model in addressing concerns about higher administrative costs for smaller utilities,
since some IOUs are small and some POUs are large. Figure 2 shows the share of utilities of each
ownership model for selected utility size ranges. Table 1 shows the total number of utilities of
each ownership model in the selected size ranges.
Previous legislation has included different utility size thresholds for inclusion. Utilities that did
not meet the specified size threshold would not have had a compliance obligation under those

Authority (TVA) deliver electricity to consumers, but these are special circumstances.
32 The Edison Electric Institute, a trade association for IOUs, maps the service territories of IOUs in the U.S. EEI, EEI
U.S. Member Company Service Territories
, April 2019, http://www.eei.org/about/members/uselectriccompanies/
Documents/EEIMemCoTerrMap.pdf. The trade association for the state’s utilities provides a perspective on Nebraska’s
status as the only state without IOUs. Nebraska Power Association, Who We Are, https://www.nepower.org/who-we-
are/about-npa.html.
33 Some states also grant IOUs monopolies on electricity generation and transmission, but others have introduced
competition into the market for these services in a process called deregulation or restructuring. Federal portfolio
standard proposals to date have not distinguished applicability based on whether competition for generation and
transmission exists. This report uses the term utility to refer to distribution utilities, regardless of whether those utilities
also own generation and transmission assets.
34 WM Warwick et al., Electricity Distribution System Baseline Report, Pacific Northwest National Laboratory, July
2016, Table 2.1, https://www.energy.gov/sites/prod/files/2017/01/f34/
Electricity%20Distribution%20System%20Baseline%20Report.pdf.
35 The median number of customers served by utilities of each ownership model is 400,000 for IOUs, 2,000 for munis,
and 13,000 for co-ops. WM Warwick et al., Electricity Distribution System Baseline Report, Pacific Northwest
National Laboratory, July 2016, https://www.energy.gov/sites/prod/files/2017/01/f34/
Electricity%20Distribution%20System%20Baseline%20Report.pdf.
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proposals. For example, S. 2146 in the 112th Congress would have initially included utilities with
at least 2 million megawatt-hours (MWh) of sales and then phased in smaller utilities of at least 1
million MWh of sales. The provisions of Title I of the Public Utility Regulatory Policies Act of
1978 (PURPA; P.L. 95-617) apply to utilities with at least 0.5 million MWh of sales.
Figure 2. Share of U.S. Distribution Utilities for Selected Size Ranges
Based on 2017 Electricity Sales

Source: CRS analysis of data from EIA, Annual Electric Power Industry Report, https://www.eia.gov/electricity/
data/eia861/.
Notes: M MWh = mil ion megawatt-hours; POU = publicly owned utility; IOU = investor-owned utility.
Numbers in parentheses show the number of utilities of each ownership model included in this analysis. POUs
include EIA categories “municipal,” “political subdivision,” and “state.” Electricity sales from EIA categories
“behind the meter providers,” “community choice aggregators,” “federal power marketing authorities,” “retail
energy providers,” and “wholesale power marketer” are not included in this analysis because those entities are
generally not distribution utilities. This analysis does not account for utilities owned by the same holding
company (i.e., affiliated utilities). The sales thresholds in this analysis were selected because they were used in
previous legislation, but they are for il ustration only.
Table 1. Count of U.S. Distribution Utilities for Selected Size Ranges
Based on 2017 Electricity Sales
Ownership Model
< 0.5M MWh
0.5 - 1M MWh
1 - 2M MWh
>2M MWh
Co-op
549
152
66
39
POU
1,756
100
50
39
IOU
37
7
12
107
Source: CRS analysis of data from EIA, Annual Electric Power Industry Report, https://www.eia.gov/electricity/
data/eia861/.
Notes: M MWh = mil ion megawatt-hours; POU = publicly owned utility; IOU = investor-owned utility.
Numbers in parentheses show the number of utilities of each ownership model included in this analysis. POUs
include EIA categories “municipal,” “political subdivision,” and “state.” Electricity sales from EIA categories
“behind the meter providers,” “community choice aggregators,” “federal power marketing authorities,” “retail
energy providers,” and “wholesale power marketer” are not included in this analysis because those entities are
generally not distribution utilities. This analysis does not account for utilities owned by the same holding
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company (i.e., affiliated utilities). The sales thresholds in this analysis were selected because they were used in
previous legislation, but they are for il ustration only.

A potential consideration is the share of total U.S. electricity sales that would be covered by a
portfolio standard if utility size thresholds were established. Figure 3 shows the share of total
U.S. electricity sales associated with utilities of different sizes, for all ownership models. In 2017,
82% of U.S. electricity sales came from distribution utilities that had annual sales volumes greater
than 2 million MWh, 87% came from utilities with sales greater than 1 million MWh, and 92%
came from utilities with sales greater than 0.5 million MWh.
Figure 3. U.S. Electricity Sales by Distribution Utility Size
Based on 2017 Electricity Sales

Source: CRS analysis of data from EIA, Form EIA-861, https://www.eia.gov/electricity/data.php.
Notes: M MWh = mil ion megawatt-hours. Electricity sales from EIA categories “behind the meter providers,”
“community choice aggregators,” “federal power marketing authorities,” “retail energy providers,” and
“wholesale power marketer” are not included in this analysis because those entities are generally not distribution
utilities. The sales thresholds in this analysis were selected because they were used in previous legislation, but
they are for il ustration only.
Target and Stringency
The target of a portfolio standard refers to “how much?” and “by when?” A target might be
defined for a single year (e.g., 50% of electricity sales in 2050), or it might be phased in over
multiple interim periods (e.g., 25% of electricity sales in 2020–2029; 40% of electricity sales in
2030–2039; 80% of electricity sales in 2040–2049). Target phase-in can be implemented in
different approaches, as shown in Figure 4. Each of these approaches has different implications
for how individual source types might be affected, though actual outcomes would be influenced
by other factors such as future technology costs and electricity demand.36 Linear phase-in would
tend to benefit existing sources and mature technologies with relatively short development
timelines, such as wind and solar. These sources could be available to generate electricity and

36 Additional discussion of these implications is provided in CRS Report R41720, Clean Energy Standard: Design
Elements, State Baseline Compliance and Policy Considerations
, by Phillip Brown.
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meet near-term compliance obligations. A back-end loaded phase-in might avoid near-term
electricity price increases and allow time for commercialization of new technologies, but it might
not result in desired environmental results in the near term. A stepped phase-in could balance the
advantages and disadvantages of the other two options. It might also lead to uneven investment
patterns, with periods of relatively high project development associated with target increases
followed by periods of relatively low project development during target plateau periods.
Figure 4. Examples of Conceptual Approaches to Phasing in Targets

Source: CRS.
The stringency of a policy indicates the changes the policy might make in generation profile
compared to a business-as-usual scenario. Generally, the stringency of the policy will be
positively correlated to the costs and benefits of implementing the policy, so as policy stringency
increases, the costs and benefits will also increase.37 For example, a portfolio standard target of
50% of electricity sales by 2050 would likely cost more to implement than a target of 25% of
electricity sales by 2050, all else being equal. Similarly, a portfolio standard target of 30% of
electricity sales by 2030 would likely cost more to implement than a target of 30% of electricity
sales by 2050. At the same time, the more stringent options (i.e., the higher target percentage or
the earlier target date) could result in greater technology innovation and lower greenhouse gas
emissions than the less stringent options.
Another way to describe portfolio standards’ stringency is the net change in generation from
eligible sources.38 This approach acknowledges that the national electricity generation profile is
currently quite diverse with many types of sources. The net change is the difference between the
final requirement of the portfolio standard (i.e., the target) and the share of generation from
eligible sources before the policy is implemented. Suppose a portfolio standard required 20% of

37 Costs and benefits may or may not linearly increase with policy stringency. For example, several studies have shown
nonlinear trends in total power system costs as levels of generation from renewable sources increase to 100%. In other
words, costs increase more between an 80% target and a 100% than they do between a 60% target and an 80% target.
See examples summarized in U.S. Congress, House Committee on Energy and Commerce, Subcommittee on
Environment and Climate Change, Hearing on “Building America’s Clean Future: Pathways to Decarbonize the
Economy,”
written testimony of Armond Cohen, Executive Director Clean Air Task Force, 116th Cong., 1st sess., July
24, 2019.
38 A 2019 study found that state portfolio standards tend to overstate the policy impact on generation because they are
not expressed in terms of net change. Michael Greenstone and Ishan Nath, Do Renewable Portfolio Standards
Deliver?
, Energy Policy Institute at the University of Chicago, April 21, 2019, https://bfi.uchicago.edu/working-paper/
do-renewable-portfolio-standards-deliver/.
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generation to come from wind and solar sources by 2020. These sources contributed 10% of
electricity generation in 2019,39 so the net change required by such a portfolio standard would be
10%. The different ways to describe portfolio standard stringency could influence public
perception of it. In this example, the same target could either be described as 20% or 10%, with
potentially different implications for perceived costs and benefits.
Base Quantity of Electricity
For portfolio standards that express compliance obligation as the percentage of electricity sales
coming from clean energy sources, the base quantity is the denominator used to calculate the
compliance obligation. The base quantity of electricity can determine the amount of generation
from eligible sources a portfolio standard requires in absolute terms. It has been described as “one
of the most important and least understood facets of [portfolio standard] design.”40 The base
quantity could equal total electricity sales, but it need not. The base quantity could instead be a
specified subset of total sales. Some portfolio standard proposals have excluded electricity
generated from certain sources in the base quantity calculation (see Appendix). Under such an
approach, a utility with a compliance obligation would be incentivized to procure electricity from
sources excluded from the base quantity because doing so would lower the amount of electricity
from clean sources it would have to procure.
To illustrate this point, consider a hypothetical portfolio standard with a 50% clean energy
requirement. The compliance obligation for this portfolio standard would be expressed as

If a utility sold 10 million MWh annually and the base quantity of electricity equaled the total
sales, then the utility would have to procure 5 million MWh from clean energy sources.
If electricity from certain sources were excluded from the base quantity, the required procurement
changes. If a utility procured 1 million MWh of the 10 million MWh it sold from sources
excluded from the base quantity, then the utility would have to procure 4.5 million MWh from
clean energy sources. The portfolio standard, in this case, would incentivize the utility to procure
electricity from both kinds of sources, namely those excluded from the base quantity and those
defined as clean energy by the policy.
The utility’s incentive to procure electricity from sources excluded from the base quantity would
generally be less than the incentive to procure electricity from clean energy sources, depending
upon the cost of different energy sources and the overall portfolio standard stringency.41 If

39 EIA, “Electricity Data Browser,” https://www.eia.gov/electricity/data/browser/.
40 Center for Climate and Energy Solutions, Clean Energy Standards: State and Federal Policy Options and
Implications
, November 2019, https://www.c2es.org/document/clean-energy-standards-state-and-federal-policy-
options-and-considerations/.
41 In this example, procuring 1 million MWh from sources excluded from the base quantity has the same effect, in
terms of compliance, as procuring 0.5 million MWh from clean energy sources (the difference between the first and
second case). The utility could reduce costs by procuring electricity from the sources excluded from the base quantity
when the cost of clean energy sources was at least twice the cost of the others. If the compliance obligation were 20%,
then procuring 1 million MWh from sources excluded from the base quantity would have the same effect as procuring
0.2 million MWh from clean energy sources. The utility could reduce costs, in this case, by procuring electricity from
sources excluded from the base quantity when the cost of clean energy sources was at least five times the cost of the
others.
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policymakers wanted to provide some policy support to certain sources, but less support than
other sources receive, they might exclude certain sources from the base quantity calculation.
A related consideration is the treatment of energy efficiency (EE) and DER (including,
potentially, customer-sited energy storage). These result in reduced utility sales, so, to some
extent, they are inherently included in the base quantity calculation. Utility investments that
increased EE or generation from DER could also help the utility achieve compliance with a
portfolio standard by reducing the amount of electricity it would have to procure from clean
energy sources. For many utilities, reducing sales reduces the company’s profitability, but some
regulatory models are being developed and implemented in which profitability can be maintained
or can increase as use of EE and DER increases.42
Cost Containment Mechanisms
Future electricity demand, technology development, and technology costs are all uncertain.
Ultimately, these uncertainties result in uncertainties around the cost to consumers of a portfolio
standard, which could be an important consideration for lawmakers. To protect consumers from
undesirably high electricity costs, portfolio standards can include provisions that reduce
stringency in response to high costs. These various provisions are sometimes called safety valves.
Safety valves need not be included in legislation, since Congress could amend a law establishing
a portfolio standard in response to any concerns that developed. Including safety valves in
legislation could, however, promote regulatory certainty for covered entities and consumers,
because legislative action to address any concerns that might arise could potentially be a lengthy
process. Another option could be for Congress to explicitly authorize an agency to implement
safety valves.
An alternative compliance payment (ACP) allows a utility to pay a fee in lieu of surrendering
credits. The degree of cost control it might provide would depend on the level at which an ACP
were set. For example, if electricity generation from eligible sources were available at 5 cents per
kilowatt-hour (cents/kWh) and an ACP were 10 cents/kWh, utilities would likely procure
electricity from the eligible sources instead of paying the ACP. If, however, the ACP were 3
cents/kWh, utilities would likely pay the ACP and procure electricity from ineligible sources. Use
of ACP could be unlimited, or it could be limited to a certain share of overall compliance.
If an ACP were included in a national portfolio standard, lawmakers would also have to decide
how any collected revenue would be disbursed. One option would be to use the revenue to further
desired policy goals, for example by funding greenhouse gas reduction programs or technology
research and development. Another option would be to return the revenue to electricity consumers
as a way of further reducing the cost impacts of a portfolio standard. Other options include
treating it as general fund revenue, deficit or debt reduction, or other spending.43
Portfolio standards could include provisions to suspend or delay compliance with targets under
certain conditions. These conditions could include compliance costs reaching a specified
threshold or identification of reliability risks.

42 NARUC, Distributed Energy Resources Rate Design and Compensation, 2016, https://pubs.naruc.org/pub/
19FDF48B-AA57-5160-DBA1-BE2E9C2F7EA0.
43 Considerations about use of any revenue that might be collected via ACP are similar to considerations of use of
revenue collected from a carbon tax or fee. These considerations are discussed in more detail in CRS Report R45625,
Attaching a Price to Greenhouse Gas Emissions with a Carbon Tax or Emissions Fee: Considerations and Potential
Impacts
, by Jonathan L. Ramseur and Jane A. Leggett.
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Some cost containment for portfolio standards comes from the use of tradable credits to
demonstrate compliance, especially if a portfolio standard allows unbundled credits. A low cost
eligible source might be located outside of a utility’s service territory. When utilities can use
unbundled credits, they can demonstrate compliance by surrendering credits from this low cost
source. The alternative, namely, disallowing tradable credits, could require utilities to procure
electricity from high cost sources or could require the development of more sources than would
be required to meet electricity demand, resulting in overall higher costs for consumers. One
argument against unbundled credits is that they might not address concerns over localized
concentrations of co-pollutants from conventional generators, known as hot spots. For example, if
a utility procured electricity from an ineligible source that also emitted harmful air pollutants such
as particulate matter or nitrogen dioxide, and the utility complied with the portfolio standard with
credits associated with eligible sources located outside its service territory, hot spots might not be
reduced to the extent they might be if unbundled credits were not allowed.
Banking or borrowing could also decrease overall compliance costs. For instance, in years when
utilities had access to many credits from low cost eligible sources, relative to what were required
by the target, utilities might bank credits. If fewer credits were available in future years, relative
to what were required by the target, a utility could surrender the banked credits, resulting in lower
compliance costs. Banking could reduce a utility’s exposure to volatility that can occur in
electricity markets. This reduced risk can also reduce overall compliance costs, since a utility
would not have to take other actions to reduce its risk exposure.44 To the extent that banking or
borrowing could reduce the net change in generation, it might lead to reduced environmental
benefits and reduced incentive for technology innovation.
Alternatively, lawmakers could establish mechanisms to increase the stringency of a portfolio
standard if certain thresholds were passed. Stringency could be increased by increasing the target
to a higher percentage of electricity sales or moving the deadline to achieve the target to an earlier
year. The trigger for such an action could be credit price, greenhouse gas emissions levels,
technology development, or other thresholds.45 This might be one way to increase the desired
benefits of a portfolio standard in cases where compliance costs were unexpectedly low. It might
also create uncertainty for covered entities and potentially result in unintended consequences such
as market participants avoiding actions they might otherwise take in order to avoid triggering a
change in stringency.
Selected Policy Considerations
The previous section discussed some potential effects of different choices about design elements
for a portfolio standard. A key theme in discussion of design elements is the balance between
achieving policy objectives and minimizing electricity cost increases for consumers, assuming a
portfolio standard were implemented. The potential effects discussed in this section might be
characterized instead as the potential effect of a portfolio standard compared to business as usual.
While the previous section addressed the question “How can a portfolio standard be designed?,”
this section addresses the question “What might happen if a portfolio standard were
implemented?”

44 If banking were not allowed, a utility might invest in clean energy sources above the level required to meet its
customers’ electricity demand, or it might use financial derivatives to reduce its risk. Either option could potentially
result in higher costs to the utility that might be passed on to customers.
45 Such a mechanism, the emissions containment reserve (ECR), is part of the Regional Greenhouse Gas Initiative
(RGGI) cap-and-trade program for greenhouse gases. See CRS Report R41836, The Regional Greenhouse Gas
Initiative: Background, Impacts, and Selected Issues
, by Jonathan L. Ramseur.
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Any projections of the effects of a policy on the U.S. electric power sector are subject to
uncertainty around various factors. These include future economic activity, electricity demand,
energy costs (e.g., natural gas prices), and technology costs. Some factors may be more strongly
influenced by decisions made by foreign governments than by the federal government. For
example, international demand for electricity from solar energy could lower the cost to produce
solar panels, or countries with large critical mineral resources could impose export bans,
increasing the cost in the United States of any technology using those minerals.46
Potential Economic Effects
The overall effect on the American economy of a national portfolio standard would be influenced
by multiple factors. Increased electricity costs could reduce economic activity, depending on the
price response throughout the economy. Potential price responses are reduced electricity
consumption, increased investment in efficiency measures, or reduced spending on other goods or
services. Some price responses might have minimal effect on overall economic activity, for
example if consumers shifted spending from electricity consumption to energy efficiency
improvements.
Potential economic effects might not be uniformly distributed. There could be regional
differences in electricity price changes, given the geographic variability in energy resources.
Utilities in regions with relatively less potential to develop eligible sources (i.e., regions in which
eligible sources are relatively costlier) might buy credits from eligible generators in other regions.
The cost of credits might result in higher electricity prices for customers of the utility buying
credits. At the same time, customers of any utilities selling credits might see lower electricity
prices.47 As discussed above, the ability to use unbundled credits for compliance could reduce
overall compliance costs relative to the case where only bundled credits were allowed because
utilities across the country could take advantage of low cost eligible sources. At the same time,
unbundled credits could result in wealth transfer between different regions of the country.48 Policy
design choices might affect any potential wealth transfer. Electricity prices already vary across
the country as a result of differences in resource availability, electricity demand, and utility
regulatory models.49

46 These are two commonly discussed potential developments and were selected to demonstrate that actions by foreign
governments could serve to either increase or decrease availability of certain technologies to U.S. markets. They are
illustrative only.
47 Electricity price, or rate, is only one component of a customer’s electricity bill. A customer can experience an
increase in electricity rate and a decrease in electricity bill, and vice versa.
48 A 2012 analysis of a proposed national portfolio standard found that it would result in the largest increases in retail
electricity prices in the Central and Southern United States. Those findings were based on the particular design choices
of the proposed portfolio standard and the generation profile at the time, so they may not apply to any future portfolio
standard proposal. Anthony Paul, Karen Palmer, and Matt Woerman, Analysis of the Bingaman Clean Energy Standard
Proposal
, RFF, May 2012, https://media.rff.org/documents/RFF-DP-12-20.pdf.
49 For example, regions with large hydropower resources tend to have lower electricity prices because this is a low cost
way to generate electricity. Various factors complicate assessments of the extent to which regulatory models (i.e.,
whether a state allows competitive markets for generation) affect prices. Mine Yücel and Adam Swadley, Did
Residential Electricity Rates Fall After Retail Competition? A Dynamic Panel Analysis
, Federal Reserve Bank of
Dallas, May 2011, https://www.dallasfed.org/~/media/documents/research/papers/2011/wp1105.pdf.
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There might also be differences in cost distribution among household income levels. Generally,
poorer Americans spend a larger portion of their income on electricity than wealthier Americans,
so electricity cost increases could disproportionately affect them.50
Within the electric power sector, businesses associated with eligible sources might be positively
affected while businesses associated with ineligible sources might be negatively affected. The
affected businesses might be individual generators and also firms associated with their supply
chains. For negatively affected businesses, the potential impacts might include loss of capital
investment (sometimes referred to as stranded costs) and reduced employment. Communities
surrounding a negatively affected generator might experience negative effects such as loss of tax
revenue base and increased demands on social services.51 For positively affected businesses and
communities, the opposite might be true, namely increased capital investment, increased
employment, and other positive economic effects. Additionally, American businesses that develop
goods or services used to comply with a portfolio standard could potentially expand into
international markets, depending on whether eligible sources also experienced demand growth
internationally. Depending on policy design details, local electricity market factors, and local
energy resources, some existing businesses in the electric power sector could experience
negligible effects of a potential national portfolio standard.
Potential Environmental Effects
Proponents of portfolio standards describe multiple environmental benefits, such as reduced
greenhouse gas (GHG) emissions (i.e., climate change mitigation) and reduced air pollutants (i.e.,
improved air quality). The extent to which a portfolio standard might produce potential
environmental benefits would depend in part on choices about source eligibility and stringency.52
Potential eligible sources vary in their GHG and air pollutant emissions, as well as other attributes
such as water consumption and power density (which can affect land requirements).
Implementation could affect environmental outcomes too. For example, some eligible sources
might be deployable in either large-scale or small-scale installations, with differing effects on
environmental factors such as land use. Some would argue these potential effects should be
compared with potential effects of other energy options. A comprehensive comparison of
potential environmental effects of various energy sources is beyond the scope of this report.
Interaction with State Portfolio Standards
The conditions under which federal law preempts state law can vary, and determination of federal
preemption can be complex.53 Thirty states, three U.S. territories, and the District of Columbia are

50 In 2017, the bottom 10% of households, by income, spent an average of 3.7% of their income on electricity while the
top 10% of households spent an average of 1.4% of their income on electricity. Bureau of Labor Statistics, Consumer
Expenditure Surveys
, released September 11, 2018, https://www.bls.gov/cex/tables.htm.
51 As an example discussion of potential community impacts, see this 2017 case study on Colstrip, MT. Julia Haggerty
et al., Colstrip: The Status of Key Policies and Decision Processes, Montana State University, July 2017,
http://www.montana.edu/energycommunities/documents/Colstrip_Status_Report-FINAL.pdf.
52 Portfolio standards are limited in their ability to reduce GHG emissions, because they only directly address GHG
emissions in the electric power sector. Although GHG emissions in the electric power sector have historically
accounted for the largest percentage of total U.S. GHG emissions, electric power emissions decreased significantly
over the last decade. In 2016, the GHG emissions in the transportation sector surpassed the electric power sector (see
CRS Report R45453, U.S. Carbon Dioxide Emissions in the Electricity Sector: Factors, Trends, and Projections, by
Jonathan L. Ramseur).
53 For a discussion, see CRS Report R45825, Federal Preemption: A Legal Primer, by Jay B. Sykes and Nicole
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link to page 24 link to page 24 Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations

currently implementing mandatory portfolio standards, and an additional eight states and one
territory have voluntary versions.54 As of October 2020, 11 of these jurisdictions have a final
target of 100%: California, Colorado, the District of Columbia, Hawaii, Maine, Massachusetts,
New Mexico, New York, Puerto Rico, Virginia, and Washington. Six states have non-binding
goals of 100% eligible clean energy for electricity generation: Connecticut, Maine, Nevada, New
Jersey, Rhode Island, and Wisconsin. If Congress implemented a national portfolio standard, it
could expressly preempt existing state portfolio standards. If a national portfolio standard were
enacted that did not preempt state portfolio standards, utilities in states with existing portfolio
standards might have to comply with both simultaneously.55 In practice, whichever standard had
the higher stringency would determine the amount of eligible sources in a utility’s portfolio. In
this case, the relevant stringency could be either the required percentage of generation from
eligible sources or the set of eligible sources itself. For example, some existing state portfolio
standards include nuclear energy as an eligible source. If a national portfolio standard did not
include nuclear energy, then a utility might be out of compliance with the federal standard even if
it were in compliance with the state standard and the state and federal standard required the same
amount of electricity from eligible sources. Assuming a generator were eligible for both a state
and national program, a utility could procure electricity (or credits) from that generator to
demonstrate compliance with both. In other words, the presence of two portfolio standards would
not necessarily double the amount of procurement from eligible sources required. A utility
covered under two portfolio standards might, however, face increased administrative costs
associated with compliance.56
Although few technical barriers exist to the simultaneous operation of state and federal portfolio
standards,57 other concerns may make this undesirable. Administrative cost burden for covered
entities is one such concern. Another might be confusion for eligible sources about whether and
how to receive credits for two portfolio standards. If Congress chose to preempt state programs,
this could potentially disrupt project finances for recently developed or proposed sources and lead
to investment losses in clean energy industries. Congress might also consider exempting utilities
facing state portfolio standards of equal or greater stringency than the federal portfolio standards.
Congress could also allow credits issued by states to be used for compliance with a federal
program. This option would, effectively, allow a utility to use one credit to demonstrate
compliance with two portfolio standards, though it could also reduce the policy outcomes relative
to a utility having two distinct compliance obligations. An option included in some of the bills
listed in the Appendix is to compensate utilities facing a state standard with a specified number
of federal credits. Alternatively, Congress could choose not to explicitly address the question, and
instead let state governments or judicial review decide whether state programs would be
suspended if a national one were implemented.

Vanatko.
54 DSIRE, Renewable and Clean Energy Standards, September 2020, https://s3.amazonaws.com/ncsolarcen-prod/wp-
content/uploads/2020/09/RPS-CES-Sept2020.pdf.
55 Most of the bills listed in the Appendix included a provision specifying they would not preempt state portfolio
standards or certain other state and local laws and regulations.
56 Administrative costs might include staff resources used to procure and submit credits and fees associated with credit
verification.
57 A chief technical consideration is the ability of registries to distinguish different compliance requirements. Some
existing state portfolio standards have different requirements (e.g., tiers), and the different companies providing
registries already accommodate them in existing tracking systems.
Congressional Research Service
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link to page 21 Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations

Interaction with Other State Energy Policies
Under current law, state and local governments have authority for approving electricity
generation and transmission assets.58 Compliance with a national portfolio standard might require
new generation and transmission assets, but it is unclear to what extent state approval processes
would consider national clean energy policy goals. Some stakeholders have argued that state
approval processes for new electricity transmission lines, in particular, create barriers for
deployment of certain electricity generation sources, especially wind.59 To the extent that a
national portfolio standard required new transmission capacity, interest might increase in a
stronger federal role in approving electricity transmission infrastructure. Congress has considered
this in the past. For example, the Energy Policy Act of 2005 (P.L. 109-58) authorized federal
approval for some transmission infrastructure under certain conditions, though this authority has
never been used.60 As noted in “Potential Environmental Effects” a national portfolio standard
might alternatively incentivize distributed energy development or projects in other locations that
might not require new transmission capacity.
Some states have adopted policies to create competition among electricity generators, an effort
known as deregulation or restructuring. In these states (and some portions of states), competitive
electricity markets create price signals meant to, among other things, drive long-term investment
decisions. Congress demonstrated support for restructuring efforts in the Energy Policy Act of
1992 (P.L. 102-486). Portfolio standards require utilities to purchase electricity from sources that
might be more expensive than other sources. This creates so-called out-of-market payments,
sometimes characterized as subsidies, for eligible sources that could distort the operation of
electricity markets.61 Eligible sources would still compete with each other for market share,
creating some competitive pressure on prices among eligible sources.

58 The Federal Power Act, as amended in 1935, grants the Federal Power Commission (now the Federal Energy
Regulatory Commission) authority over transmission rates and other matters affecting interstate sales of electricity. It
did not extend federal authority to matters then regulated by states, such as siting of generation and transmission
infrastructure. 16 U.S.C. §824. For additional background see CRS Report R44783, The Federal Power Act (FPA) and
Electricity Markets
, by Richard J. Campbell.
59 See, for example, Johannes Pfeifenberger and Judy Chang, Well-Planned Electric Transmission Saves Customer
Costs: Improved Transmission Planning Is Key to the Transition to a Carbon-Constrained Future
, The Brattle Group
for WIRES, June 2016, https://wiresgroup.com/docs/reports/
WIRES%20Brattle%20Report_TransmissionPlanning_June2016.pdf.
60 See discussion in Alexandra B. Klass and Jim Rossi, “Reconstituting the Federalism Battle in Energy
Transportation,” Harvard Environmental Law Review, vol. 41 (2017), pp. 453 - 455, https://harvardelr.com/wp-
content/uploads/sites/12/2017/08/KlassRossi_final.pdf.
61 A portfolio standard differs from subsidies in that the value of credits that generators of eligible sources could
receive fluctuates in response to the relative supply of and demand for generation from eligible sources.
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link to page 25 link to page 25 Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations

Appendix. Legislative Proposals in the 105th-116th
Congresses
This section lists previously introduced legislation that would have established national portfolio
standards. CRS searched congress.gov using the phrases “renewable portfolio standard,” “clean
energy standard,” “renewable energy standard,” “renewable electricity standard,” “renewable
energy,” and “clean energy,” in full bill text or bill summaries for all Congresses. The earliest bill
identified in this search was introduced in the 105th Congress. Search results were refined by
including only the Subject-Policy Area terms “Energy” and “Environmental Protection.Table A-
1
provides selected policy design elements of the bills that would have established national
portfolio standards that were identified using this search methodology. Bills are listed in order of
introduction by Congress, with House bills listed first and Senate bills listed second. This table
only provides information related to the bills’ portfolio standards. Some of the bills in the table
had multiple provisions, including some that might also affect the electric power sector, but those
are not described here.

Congressional Research Service
21


Table A-1. Renewable Portfolio Standard and Clean Energy Standard Bills from the 105th Through 116th Congresses
Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
116th Congress (as of October 24, 2020)
H.R. 330
Climate Solutions Act of 2019
100% in 2035 and thereafter
Renewable sources (no further specification)
Lieu
H.R. 2597
Clean Energy Standard Act of 2019
100%, target date varies by utility (behind-the-meter
Solar, wind, ocean, current, wave, tidal,
Luján
generation included in base quantity)
geothermal, qualifying biomass, hydropower,
nuclear, qualifying waste-to-energy, qualifying
low-carbon fuels, qualifying combined heat
and power, any other source with a carbon
intensity less than 0.4 metric tons of carbon
dioxide equivalent per megawatt-hour
H.R. 7516
Clean Energy Innovation and
100% in 2050 and thereafter
Solar, wind, ocean, current, wave, tidal,
DeGette
Deployment Act of 2020
geothermal, nuclear, qualifying hydropower,
qualifying waste-to-energy, qualifying low-
carbon fuels, qualifying combined heat and
power, qualifying biomass, any other source
with a carbon intensity less than 0.82 metric
tons of carbon dioxide equivalent per
megawatt-hour
S. 1359
Clean Energy Standard Act of 2019
100%, target date varies by utility (behind-the-meter
Solar, wind, ocean, current, wave, tidal,
Smith
generation included in base quantity)
geothermal, qualifying biomass, hydropower,
nuclear, qualifying waste-to-energy, qualifying
low-carbon fuels, qualifying combined heat
and power, any other source with a carbon
intensity less than 0.4 metric tons of carbon
dioxide equivalent per megawatt-hour
S. 1974
Renewable Electricity Standard Act
1.5 percentage points greater than 2019 levels in
Solar, wind, ocean, tidal, geothermal,
Udall
2020; increasing by 2 percentage points annually for
qualifying biomass, landfil gas, qualifying
2021-2029 and by 2.5 percentage points annually for
hydropower, hydrokinetic, qualifying energy
2030-2035 (voluntary customer purchases of
efficiency
electricity from renewable sources excluded from
base quantity)
CRS-22


Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
115th Congress (2017-2018)
H.R. 2746
American Renewable Energy and
35% in 2032-2042, and provides option that FERC
Wind, solar, geothermal, qualifying biomass,
Welch
Efficiency Act
could set higher requirements during those years
qualifying biogas, qualifying biofuels, qualifying
(existing hydropower and waste-to-energy using
hydropower, ocean, landfil gas
municipal solid waste excluded from base quantity)
H.R. 2958
Climate Solutions Act of 2017
80% in 2050 and thereafter
Renewable sources (no further specification)
Lieu
114th Congress (2015-2016)
H.R. 1971
Climate Solutions Act of 2015
80% in 2050 and thereafter
Renewable sources (no further specification)
Lieu
H.R. 3426
American Renewable Energy and
30% in 2030-2040, and provides option that FERC
Wind, solar, geothermal, qualifying biomass,
Welch
Efficiency Act
could set higher requirements during those years
qualifying biogas, qualifying biofuels, qualifying
(existing hydropower and waste-to-energy using
hydropower, ocean, landfil gas
municipal solid waste excluded from base quantity)
S. 1264
Renewable Electricity Standard Act
30% in 2030-2039 (existing hydropower and waste-
Solar, wind, ocean, geothermal, qualifying
Udall
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
Hearings held
base quantity)
113th Congress (2013-2014)
H.R. 3654
Renewable Electricity Standard Act of
25% in 2025-2039 (existing hydropower and waste-
Solar, wind, ocean, geothermal, qualifying
Polis
2013
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
base quantity)
H.R. 5072
American Renewable Energy and
25% in 2025-2040, and provides option that FERC
Wind, solar, geothermal, qualifying biomass,
Welch
Efficiency Act
could set higher requirements during those years
qualifying biogas, qualifying biofuels, qualifying
(existing hydropower and waste-to-energy using
hydropower, ocean, landfil gas
municipal solid waste excluded from base quantity)
H.R. 5301
American Renewable Energy and
25% in 2025-2040, and provides option that FERC
Wild, solar, geothermal, qualifying biomass,
Welch
Efficiency Act
could set higher requirements during those years
qualifying biogas, qualifying biofuels, qualifying
(existing hydropower and waste-to-energy using
hydropower, ocean, landfil gas
municipal solid waste excluded from base quantity)
CRS-23


Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
S. 1595
Renewable Electricity Standard Act of
25% in 2025-2039 (existing hydropower and waste-
Solar, wind, ocean, geothermal, qualifying
Udall
2013
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
base quantity)
S. 1627
American Renewable Energy and
25% in 2025-2040, and provides option that FERC
Wind, solar, geothermal, qualifying biomass,
Markey
Efficiency Act
could set higher requirements during those years
qualifying biogas, qualifying biofuels, qualifying
(existing hydropower and waste-to-energy using
hydropower, ocean, landfil gas
municipal solid waste excluded from base quantity)
112th Congress (2011-2012)
H.R. 5967
American Renewable Energy and
50% in 2035-2040 (existing hydropower, waste-to-
Wind, solar, geothermal, qualifying biomass,
Markey
Efficiency Act
energy using municipal solid waste, new nuclear
qualifying biogas, qualifying biofuels, qualifying
excluded from base quantity)
hydropower, ocean, landfil gas
S. 559
Securing America’s Future with Energy 25% in 2025 (existing hydropower excluded from
Solar, wind, geothermal, ocean, qualifying
Klobuchar
and Sustainable Technologies Act
base quantity)
biomass, landfil gas, waste-to-energy using
municipal solid waste, qualifying hydropower
S. 741
N/A
25% in 2025-2039 (existing hydropower and waste-
Solar, wind, ocean, geothermal, qualifying
Udall
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
base quantity)
S. 2146
Clean Energy Standard Act of 2012
84% in 2035 (existing hydropower and existing
Solar, wind, ocean, current, wave, tidal
Bingaman
nuclear excluded from base quantity)
geothermal, qualifying biomass, natural gas,
Hearings held
hydropower, nuclear, qualifying waste-to-
energy, qualifying combined heat and power,
CCS, “a source of energy, other than
biomass, with lower annual carbon intensity
than 0.82 metric tons of carbon dioxide
equivalent per megawatt-hour”
111th Congress (2009-2010)
H.R. 890
American Renewable Energy Act
25% in 2025-2039 (existing hydropower and waste-
Wind, solar, geothermal, qualifying biomass,
Markey
to-energy using municipal solid waste excluded from
landfil gas, qualifying hydropower, ocean
base quantity)
H.R. 2454
American Clean Energy and Security
20% in 2021-2039 (some hydropower, new nuclear,
Wind, solar, geothermal, qualifying biomass,
Waxman
Act of 2009
and CCS excluded from base quantity)
qualifying biogas, qualifying biofuels, qualifying
Passed House
hydropower, marine and hydrokinetic
CRS-24


Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
S. 20
Clean Energy Standard Act of 2010
50% in 2050 (existing hydropower and waste-to-
Solar, wind, geothermal, ocean, qualifying
Graham
energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower,
base quantity)
coal-mined methane, qualifying waste-to-
energy, new nuclear, advanced coal, eligible
retired fossil fuel, “another clean energy
source based on innovative technology as
determined by the Secretary through
rulemaking”
S. 433
N/A
25% in 2025-2039 (existing hydropower and waste-
Solar, wind, ocean, geothermal, qualifying
Udall
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
base quantity)
S. 826
American Renewable Energy Act of
25% in 2025 (existing hydropower excluded from
Solar, wind, geothermal, ocean, qualifying
Klobuchar
2009
base quantity)
biomass, landfil gas, waste-to-energy using
municipal solid waste, qualifying hydropower
S. 1462
American Clean Energy Leadership
15% in 2021-2039 (existing hydropower, waste-to-
Solar, wind, geothermal, ocean, qualifying
Bingaman
Act of 2009
energy using municipal solid waste, qualifying fossil
biomass, landfil gas, qualifying hydropower,
Reported out of
fuel with CCS, new nuclear excluded from base
coal-mined methane, qualifying waste-to-
committee
quantity)
energy, other sources as determined by the
Secretary via rulemaking
S. 3464
Practical Energy and Climate Plan Act
50% in 2050 (existing hydropower excluded from
Advanced coal, biomass, coal mine methane,
Lugar
of 2010
base quantity)
efficiency, geothermal, landfil gas, biogas,
ocean, qualified hydropower, new nuclear,
solar, waste-to-energy, wind, “any other
source that wil result in at least a 80%
reduction in greenhouse gas emissions
compared to average emissions of freely
emitting sources in the calendar year prior to
certification of the Secretary”
S. 3576
Securing America’s Future with Energy 25% in 2025 (existing hydropower excluded from
Solar, wind, geothermal, ocean, qualifying
Klobuchar
and Sustainable Technologies Act
base quantity)
biomass, landfil gas, waste-to-energy using
municipal solid waste, qualifying hydropower
CRS-25

link to page 34
Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
S. 3813
Renewable Electricity Promotion Act
15% in 2021-2039 (existing hydropower, CCS, new
Solar, wind, geothermal, ocean, qualifying
Bingaman
of 2010
nuclear excluded from base quantity)
biomass, landfil gas, qualifying hydropower,
coal-mined methane, qualifying waste-to-
energy, other sources as determined by the
Secretary via rulemaking
110th Congress (2007-2008)
H.R. 6
Energy Independence and Security Act 15% in 2020-2039 (existing hydropower and waste-
Solar, wind, ocean, tidal, geothermal,
(Engrossed
of 2007
to-energy using municipal solid waste excluded from
qualifying biomass, landfil gas, incremental
Amendment
base quantity)
hydropower, hydrokinetic energy, qualifying
House bil )a
energy efficiency
Rahall
Passed House
H.R. 969
N/A
20% in 2020 and thereafter (existing hydropower
Solar, wind, ocean, geothermal, qualifying
Udall
excluded from base quantity)
biomass, landfil gas, qualifying hydropower
H.R. 1133
Freedom through Renewable Energy
20% in 2016-2031 (existing hydropower and waste-
Solar, wind, geothermal, ocean, qualifying
Berkley
Expansion (FREE) Act
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
base quantity)
H.R. 1590
Safe Climate Act of 2007
20% in 2020 and thereafter
Renewable sources (no further specification)
Waxman
H.R. 2809
New Apol o Energy Act of 2007
20% in 2020-2030 (existing hydropower and waste-
Solar, wind, geothermal, ocean, qualifying
Inslee
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
base quantity)
H.R. 2950
Renewable Fuels, Consumer
15% in 2020-2030 (existing hydropower excluded
Solar, wind, geothermal, ocean, qualifying
Wilson
Protection, and Energy Efficiency Act
from base quantity)
biomass, landfil gas, qualifying hydropower
of 2007
H.R.
Housing and Economic Recovery Act
15% in 2020-2039 (existing hydropower and waste-
Solar (including solar water heating), wind,
3221(Engrossed
of 2008
to-energy using municipal solid waste excluded from
ocean, tidal, geothermal, qualifying biomass,
House bil )
base quantity)
landfil gas, incremental hydropower,
Pelosi
qualifying energy efficiency
Passed House
CRS-26


Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
H.R. 6899
Comprehensive American Energy
15% in 2020-2039 (existing hydropower and waste-
Solar, wind, ocean, geothermal, qualifying
Rahall
Security and Consumer Protection
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower,
Passed House
Act
base quantity)
hydrokinetic
H.R. 7239
American Energy, American
20% in 2020 and thereafter (existing hydropower
Solar, wind, ocean, geothermal, qualifying
Udall
Innovation Act of 2008
excluded from base quantity)
biomass, landfil has, qualifying hydropower
S. 309
Global Warming Pol ution Reduction
20% in 2020 and thereafter
Solar, wind, qualifying biomass, landfil gas,
Sanders
Act
ocean, geothermal, qualifying hydropower
S. 485
Global Warming Reduction Act of
20% in 2021 and thereafter
Solar, wind, qualifying biomass, landfil gas,
Kerry
2007
ocean, geothermal, qualifying hydropower
S. 1201
Clean Power Act of 2007
20% in 2020 and thereafter
Solar, wind, qualifying biomass, landfil gas,
Sanders
ocean, geothermal, qualifying hydropower
S. 1554
Energy Independence, Clean Air, and
20% in 2020-2030 (existing renewables and existing
Solar, wind, ocean, geothermal, qualifying
Col ins
Climate Security Act of 2007
hydropower excluded from base quantity)
biomass, landfil gas, qualifying hydropower
S. 1567
N/A
25% in 2025 (waste-to-energy using municipal solid
Solar, wind, geothermal, ocean, qualifying
Klobuchar
waste and existing hydropower excluded from base
biomass, landfil gas, qualifying hydropower
quantity)
S. 1602
Clean, Reliable, Efficient and Secure
20% in 2030 and thereafter
Solar, wind, ocean, geothermal, fuel cells,
Hagel
Energy Act of 2007
solid waste, renewable natural gas, landfil gas,
qualifying hydropower, qualifying coal- or gas-
fired generation facility capable of future CCS,
new nuclear
S. 2642
American Renewable Energy Act of
20% in 2024 (waste-to-energy using municipal solid
Solar, wind, geothermal, ocean, qualifying
Klobuchar
2008
waste and existing hydropower excluded from base
biomass, landfil gas, qualifying hydropower
quantity)
109th Congress (2005-2006)
H.R. 983
N/A
20% in 2027 and thereafter
Solar, wind, ocean, geothermal, qualifying
Udall
biomass, landfil gas, qualifying hydropower
CRS-27


Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
H.R. 2828
New Apol o Energy Act of 2005
10% in 2022; Secretary may establish regulations
Solar, wind, ocean, geothermal, qualifying
Inslee
requiring not less than 10% for 2022-2030 (existing
biomass, landfil gas, qualifying hydropower
renewables and existing hydropower excluded from
base quantity)
H.R. 4384
Energy for Our Future Act
20% in 2030 (existing renewables and hydropower
Solar, wind, ocean, geothermal, qualifying
Shays
excluded from base quantity)
biomass, landfil gas, qualifying hydropower
H.R. 5642
Safe Climate Act of 2006
20% in 2020 and thereafter
Renewable sources (no further specification)
Waxman
H.R. 5926
Freedom through Renewable Energy
20% in 2015 and thereafter (existing hydropower and
Solar, wind, geothermal, ocean, qualifying
Berkley
Expansion (FREE) Act
waste-to-energy using municipal solid waste excluded
biomass, landfil gas, qualifying hydropower
from base quantity)
H.R. 5927
American Energy Independence Act
25% in 2020 and thereafter (existing hydropower
Solar, wind, geothermal, ocean, qualifying
Cardin
excluded from base quantity)
biomass, landfil gas, qualifying hydropower
S. 427
Renewable Energy Investment Act of
20% in 2020 and thereafter (existing hydropower
Wind, ocean, qualifying biomass, solar, landfil
Jeffords
2005
excluded from base quantity)
gas, qualifying hydropower, geothermal,
hydrogen produced from one of the above
energy sources
S. 2747
Enhanced Energy Security Act of 2006
10% in 2020-2030 (existing hydropower and waste-
Solar, wind, geothermal, ocean, qualifying
Bingaman
to-energy using municipal solid waste excluded from
biomass, landfil gas, qualifying hydropower
Hearings held
base quantity)
S. 3698
Global Warming Pol ution Reduction
20% in 2020 and thereafter
Solar, wind, qualifying biomass, landfil gas,
Jeffords
Act
ocean, geothermal, qualifying hydropower
S. 4039
Global Warming Reduction Act
20% in 2020 and thereafter
Solar, wind, geothermal, ocean, qualifying
Kerry
biomass, landfil gas, qualifying hydropower
108th Congress (2003-2004)
H.R. 6
Energy Policy Act of 2003
10% in 2020; Secretary may establish regulations
Solar, wind, ocean, geothermal, qualifying
Tauzin
requiring not less than 10% for 2020-2030
biomass, landfil gas, qualifying hydropower
Conference report
agreed to in House

CRS-28


Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
H.R. 1294
N/A
20% in 2025
Solar, wind, ocean, geothermal, qualifying
Udall
biomass, landfil gas, qualifying hydropower
S. 944
Renewable Energy Investment Act of
20% in 2020 and thereafter (hydropower excluded
Wind, ocean, qualifying biomass, solar, landfil
Jeffords
2003
from base quantity)
gas, qualifying hydropower, geothermal,
hydrogen produced from one of the above
sources
107th Congress (2001-2002)
H.R. 4
Energy Policy Act of 2002
10% in 2020; Secretary may establish regulations
Solar, wind, biomass, geothermal
Tauzin
requiring not less than 10% for 2020-2030
Conference
committee
conference held

H.R. 2478
Comprehensive Renewable Energy
20% in 2020 and thereafter (existing hydropower
Wind, qualifying biomass, geothermal, solar,
Woolsey
and Energy Efficiency Act of 2001
excluded from base quantity)
incremental hydropower
H.R. 3037
Renewable Energy and Energy
20% in 2020 and thereafter
Wind, qualifying biomass, landfil gas,
Pallone
Efficiency Investment Act of 2001
geothermal, solar, hydrogen produced from
one of the above sources
H.R. 3274
Comprehensive Energy Conservation
20% in 2020 and thereafter
Solar, wind, geothermal, biomass
Sanders
Act for the 21st Century
H.R. 5756
N/A
20% in 2025
Solar, wind, ocean, geothermal, qualifying
Udall
biomass, landfil gas, qualifying hydropower
S. 1333
Renewable Energy and Energy
20% in 2020 and thereafter
Wind, qualifying biomass, landfil gas,
Jeffords
Efficiency Investment Act of 2001
geothermal, solar, hydrogen produced from
one of the above sources
S. 1766
Energy Policy Act of 2002
20% in 2020 (existing solar, existing wind, existing
Solar, wind, biomass, ocean, geothermal,
biomass, existing ocean, existing geothermal, waste-
distributed renewable energy, qualifying
to-energy using landfil gas, and hydropower excluded
hydropower
from base quantity)
CRS-29


Bill, Sponsor,
Latest Action

Short Title
Final Target
Eligible Sources
106th Congress (1999-2000)
H.R. 1828
Comprehensive Electricity
7.5% in 2010-2015
Solar, wind, geothermal, biomass
Bliley
Competition Act
Hearings held
H.R. 2050
Electric Consumers’ Power to
3% in 2005 and thereafter
Solar, wind, geothermal, biomass
Largent
Choose Act of 1999
Hearings held
H.R. 2569
Fair Energy Competition Act of 1999
7.5% in 2010 and thereafter (hydropower excluded
Wind, qualifying waste-to-energy, biomass,
Pallone
from base quantity)
landfil gas, geothermal, solar
H.R. 2645
Electricity Consumer, Worker, and
8 percentage points greater than the 1997 baseline by
Waste-to-energy, energy crops, landfil gas,
Kucinich
Environmental Protection Act of 1999
2010; increasing by 1 percentage point annually
geothermal, solar, wind
thereafter
H.R. 4861
Clean Power Act
6% in 2010 and thereafter
Solar, wind, geothermal, biomass
Lazio
S. 1369
Clean Energy Act of 1999
20% in 2020 and each year thereafter (hydropower
Wind, qualifying biomass, geothermal, solar
Jeffords
excluded from base quantity)
Hearings held
S. 2904
Energy Security Tax and Policy Act of
5% in 2012-2015 (existing solar, wind, geothermal,
Solar, wind, geothermal, qualifying biomass,
Bingaman
2000
biomass, and hydropower excluded from base
incremental hydropower, incremental
quantity)
renewable
105th Congress (1997-1998)
H.R. 4798
Electricity Consumer, Worker, and
8 percentage points greater than the 1997 baseline by
Qualifying biomass, landfil gas, geothermal,
Kucinich
Environmental Protection Act of 1998
2010; increasing by 1 percentage point annually
solar, wind
thereafter
S. 687
Electric System Public Benefits
20% in 2020 and thereafter (hydropower excluded
Wind, qualifying waste-to-energy, qualifying
Jeffords
Protection Act of 1997
from base quantity)
biomass, geothermal, solar
S. 2287
Comprehensive Electricity
5.5% in 2010-2015
Solar, wind, geothermal, biomass
Murkowski
Competition Act
Source: Congress.gov.
CRS-30


Notes: N/A = Not applicable; FERC = Federal Energy Regulatory Commission; CCS = carbon capture and sequestration. Only the latest major action, other than
“Introduced,” is shown. Some bil s with an action listed had multiple actions. Some bil s include specific definitions or requirements for some eligible sources (e.g.,
biomass, geothermal, hydropower, ocean energy). For simplicity, the table omits these details, and refers to these sources as “qualifying.” Some bil s specified that final
targets would have stayed in place permanently, and these are indicated by “and thereafter” in this table. Other bil s did not specify what should occur after the final
target year.
a. The final version of this bil was enacted as P.L. 110-140, without a portfolio standard provision.

CRS-31

Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations



Author Information

Ashley J. Lawson

Analyst in Energy Policy



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Congressional Research Service
R45913 · VERSION 4 · UPDATED
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