Clean Energy Standards: Selected Issues for the 117th Congress

Clean Energy Standards: Selected Issues for the 117th Congress

Clean Energy Standards: Selected Issues for the November 2, 2021
117th Congress
Ashley J. Lawson
For many years, policies to reduce greenhouse gas (GHG) emissions have been of interest to
Analyst in Energy Policy
Congress. Congressional and constituent interest continues in the 117th Congress. One option to

reduce GHG emissions from electricity generation is a clean energy standard.

A clean energy standard (CES), sometimes called a clean electricity standard, is a policy that
requires a minimum share of electricity to be generated from eligible “clean” sources. No universal definition of clean energy
exists, and proposals differ in what technologies are included. Some proposals, usually referred to as a renewable portfolio
standard (RPS), include only certain renewable energy sources (e.g., solar), while other proposals also include nuclear power,
fossil fuels equipped with carbon capture and storage (CCS) technology, certain natural gas technologies, or other energy
sources. As of 2020, thirty states and the District of Columbia have implemented a CES, including 10 jurisdictions that will
ultimately require 100% of covered electricity sales to come from eligible clean energy sources. In addition, eight states have
nonbinding goals of carbon-free electricity, and many utilities have committed to reducing their GHG emissions to varying
degrees and over different time frames. State targets and utility goals cover 77% of total U.S. electricity sales, with 69% of
total sales covered by a carbon-free target or goal.
Members of Congress have demonstrated a long-standing interest in CES policies, with proposals for a national CES dating
at least to 1997. None has been enacted. Most recently, four bills introduced to date in the 117th Congress would establish a
national CES (sometimes in conjunction with other policies). The measures differ in eligible sources, final targets, and
implementation details. For example, one bill would require 70% of covered electricity sales to come from new renewable
energy sources by 2030. Another bill would establish CES targets consistent with 80% reductions in electricity GHG
emissions. The 116th Congress considered but did not enact seven similar CES bills.
The Biden Administration has expressed support for a 100% CES as part of its commitment to reduce U.S. GHG emissions
by 50%-52% from 2005 levels by 2030. A Clean Electricity Performance Program (CEPP) was proposed to help achieve this
goal. The proposed CEPP would aim to achieve the same goals as a CES but through a different policy structure (one
designed to meet requirements for passage through budget reconciliation). For context, renewable sources made up 21% of
U.S. electricity generation in 2020, nuclear power made up 20%, natural gas made up 40%, and coal (without CCS) made up
19%. In February 2021, the U.S. Energy Information Administration (EIA) projected the share of total U.S. electricity
generation coming from renewable sources in 2050 might vary from 33% to 57%, depending on factors such as future energy
prices and economic growth. The share from all nonemitting sources (i.e., renewables and nuclear) in 2050 varied from 44%
to 67% in the projections, and the share from nonemitting sources together with natural gas varied from 86% to 93%.
Concerns and criticisms raised against a CES include its potential to reduce elect ric reliability, increase electricity rates, and
negatively impact environmental justice efforts. To a certain extent, a CES policy can be designed to address these concerns,
and some bills have included provisions to do so. Efforts to address one impact could exacerbate others, though uncertainty
remains on potential impacts of any specific policy. For example, multiple studies have evaluated the cost of achieving a
100% CES policy, with estimates ranging from $106 billion to over $2 trillion in cumulative costs. Some studies have also
estimated monetary benefits of a 100% CES, finding $715 billion to $1.7 trillion in cumulative benefits. In all cases where
costs and benefits were both estimated, studies found that benefits outweighed costs.
The future makeup of the U.S. electricity system might affect congressional perceptions of the necessity or feasibility of a
CES. Estimating the future energy system makeup typically is challenging, especially over 15 years or more (i.e., the time
periods covered by recent CES proposals). Another complicating factor is the possibility that the 117th Congress could
change U.S. energy policy (not including consideration of a CES). For example, infrastructure legislation under consideration
aims to accelerate deployment of certain kinds of clean energy technologies. Additionally, noncongressional action, such as
executive actions or state policies, could affect the U.S. electricity system. The interactions among some or all of these
factors might be relevant, should Congress choose to debate a CES.
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Contents
Introduction ................................................................................................................... 1
Bills Introduced in the 117th and 116th Congresses ................................................................ 2
Potential Considerations................................................................................................... 4
Putting a 100% Target in Context ...................................................................................... 8
Current Clean Energy Use........................................................................................... 8
State Targets and Utility Commitments ......................................................................... 9
Outlook for Clean Energy in the U.S. Electricity System ............................................... 10
Concluding Observations .......................................................................................... 12

Figures
Figure 1. 2020 U.S. Electricity Generation by Source Type.................................................... 9
Figure 2. Projected Share of Total U.S. Electricity Generation, by Source Type ...................... 11

Tables
Table 1. National Clean Energy Standard (CES) Legislative Proposals in the 117th and
116th Congresses........................................................................................................... 3
Table 2. Cost and Benefit Estimates for 100% Clean Energy Standards ................................... 6

Contacts
Author Information ....................................................................................................... 12

Congressional Research Service

Clean Energy Standards: Selected Issues for the 117th Congress

Introduction
Congress continues to study and discuss a range of policies to reduce U.S. greenhouse gas (GHG)
emissions, and the Biden Administration has made reducing GHG emissions a priority. Several
legislative and executive actions could achieve such a goal. One legislative option, targeting the
U.S. electricity system, is a clean energy standard.
A clean energy standard (CES), sometimes cal ed a clean electricity standard, aims to increase the
share of U.S. electricity generated from qualified clean energy sources. No agreed-upon definition
of “clean energy” exists, so the exact set of energy sources supported by a CES proposal is one of
its defining characteristics. Members of Congress have introduced legislation to establish a
national clean energy standard in every Congress since at least the 105th (1997-1998).1
The Biden Administration has expressed support for a CES as a key policy to reduce U.S. GHG
emissions by 50%-52% from 2005 levels by 2030, the target President Biden announced pursuant
to the Paris Agreement.2 For example, the American Jobs Plan includes a 100% CES, and the
Department of Energy’s FY2022 budget request included funding for “programmatic
infrastructure” for a CES.3 An executive order issued January 27, 2021, also states the goal to
“achieve or facilitate a carbon pollution-free electricity sector no later than 2035.”4 A Clean
Electricity Performance Program (CEPP; also cal ed a Clean Electricity Payment Program)—
which would aim to achieve similar outcomes as the Biden Administration’s proposed CES, albeit
through a different policy structure—was proposed as part of the FY2022 budget reconciliation
process. Details of the program were included in House Committee on Energy and Commerce
budget reconciliation legislative recommendations, debated in August 2021. The CEPP text was
not included, however, in updated budget reconciliation language released in October 2021 by the
House Rules Committee.5
As of 2020, 30 states and the District of Columbia have a CES.6 Of these, 12 are to require al
covered electricity sales to come from eligible clean energy sources: California, Colorado, the

1 Seven of these measures were passed in at least one chamber, in all cases as part of comprehensive energy or
environmental legislation. No CES provision was enacted into law. For more information, see CRS In Focus IF11316,
A Brief History of U.S. Electricity Portfolio Standard Proposals, by Ashley J. Lawson. Past proposals have used
alternative names such as renewable portfolio standard (RPS) or clean electricity standard. An RPS includes only
renewable sources while a clean energy (or electricity) standard typically also includes nonrenewable sources like
nuclear power. Most policy considerations apply equally to RPS or CES. For simplicity, this report generally uses the
term CES to refer to any policy that would require certain sources be used for electricity generation, reflecting the
predominant usage in the proposals in the 116 th and 117th Congresses. For more information about CES, see CRS
Report R45913, Electricity Portfolio Standards: Background, Design Elem ents, and Policy Considerations, by Ashley
J. Lawson.
2 White House, “ Fact Sheet: President Biden Sets 2030 Greenhouse Gas Pollution Reduction T arget Aimed at Creating
Good-Paying Union Jobs and Securing U.S. Leadership on Clean Energy T echnologies,” April 22, 2021. For
discussion of the Paris Agreement, see CRS In Focus IF11746, United States Rejoins the Paris Agreem ent on Clim ate
Change: Options for Congress, by Jane A. Leggett .
3 T he American Jobs Plan includes an Energy Efficiency and Clean Electricity Standard aimed at “100 percent carbon -
pollution free power by 2035.” White House, “ Fact Sheet: T he American Jobs Plan,” March 31, 2021; and U.S.
Department of Energy, “ Budget in Brief,” June 2021, p. 1.
4 Executive Order 14008, “Tackling the Climate Crisis at Home and Abroad,” 86 Federal Register 7619, February 1,
2021. Campaign quote comes from https://joebiden.com/clean-energy/#, accessed January 15, 2020.
5 For further discussion, see CRS Report R46934, The Clean Electricity Performance Program (CEPP): In Brief, by
Ashley J. Lawson.
6 Some of these states have an RPS in place, setting goals for renewable energy use only. T hree U.S. territories also
have an RPS. Eight additional states and one additional territory have voluntary renewable portf olio goals in place.
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District of Columbia, Hawai , Il inois, Massachusetts, New Mexico, New York, North Carolina,
Oregon, Virginia, and Washington.7 Additional y, at least eight states have nonbinding goals of
100% covered electricity sales from eligible clean energy sources: Connecticut, Louisiana,
Maine, Michigan, Nevada, New Jersey, Rhode Island, and Wisconsin.8
Experts disagree about the extent to which achieving a 100% CES presents cost or feasibility
chal enges. Assessing the cost and feasibility of a 100% CES is beyond the scope of this report.
This report provides some analysis and discussion to inform potential CES policy debate in the
117th Congress, including a summary of CES proposals to date in the 117th and 116th Congresses.
Bills Introduced in the 117th and 116th Congresses
CRS identified four bil s introduced in the 117th Congress to date and seven bil s introduced in the
116th Congress that would establish a national clean energy standard.9 Table 1 summarizes the
CES proposals identified in these 11 bil s, focusing on two key policy features: the final target
and eligible sources. The final target is typical y expressed as the maximum required share of
covered electricity sales to come from eligible sources and the year by which that share is to be
met. Final targets for many state CES policies and past legislative proposals apply uniformly
across al utilities (i.e., al utilities have to meet the same percentage in the same year); however,
several bil s included in Table 1 set targets for each utility individual y. This distinction is noted
in the table. Eligible sources refer to the energy sources that may be used for compliance with the
CES. Bil s defined eligible sources by either source type (e.g., renewable energy, nuclear power)
or carbon intensity (i.e., the volume of GHG released per unit of electricity generated).

N.C. Clean Energy T echnology Center Database of State Incentives for Renewables & Efficiency (DSIRE), Renewable
Portfolio Standards and Clean Energy Standards, September 2020.
7 T he District of Columbia, Hawaii, Massachusetts, and Virginia each require 100% of covered electricity sales to come
from renewable energy sources. T he dates for achieving those targets vary. In some jurisdictions (e.g., Colorado, North
Carolina), only investor-owned utilities meeting size requirements are covered. In 2020, Arizona regulators approved a
100% CES, but the policy is not yet finalized. Additionally, Puerto Rico has a 100% RPS.
8 Generally, a nonbinding goal has no penalty for failing to meet it, while a binding goal or a requirement does. Some
nonbinding goals were enacted through legislation, while others were adopted by executive order. T he group Clean
Energy States Alliance (CESA) tracks state goals and provides a table with more information about state clean energy
targets. CESA, “States with 100% Clean Energy Goals,” at https://www.cesa.org/projects/100-clean-energy-
collaborative/guide/table-of-100-clean-energy-states/. As of the time of this writing, CESA identifies the eight states
listed in the body of this report. Governors in other states, such as North Dakota and Wyoming, have made public
statements supporting carbon reductions in their states, though not necessarily carbon-free electricity generation. See
Adam Willis, “Gov. Doug Burgum Calls for North Dakota to be Carbon Neutral by 2030,” Grand Forks Herald, May
12, 2021; and Mead Gruver, “Governor of T op Coal-Mining State Sets Carbon-Negative Goal,” AP, March 2, 2021.
9 Bills were identified by searching Congress.gov using the phrases “clean energy standard,” “ clean electricity
standard,” “ clean energy,” “ renewable electricity,” “ renewable energy,” and “ renewable portfolio standard” in full bill
text or bill summaries. Search results were refined by including only the Subject -Policy Area terms “ Energy” and
“Environmental Protection.” Some bills contained policy provisions other than CES, but those other policies are not
summarized in this report.
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Clean Energy Standards: Selected Issues for the 117th Congress

Table 1. National Clean Energy Standard (CES) Legislative Proposals in the 117th
and 116th Congresses
Bill
Eligible
Selected Distinguishing
Short Title
Number(s)
Final Target
Sources
Feature(s)
117th Congress
CLEAN Future Act
H.R. 1512
100% by 2035
Renewables,
Targets set individual y for every
nuclear, CCS,
electric utility. Certain sources
natural gas
must account for GHG emissions
during production and transport
of fuel. Direct air capture eligible
for credits. Eligible sources must
meet defined labor standards.
American
H.R. 3959
70% by 2030
Renewables,
Carve outs for distributed
Renewable Energy
excluding
generation and generation
Act of 2021
existing
located in defined impacted
hydropower
communities.
Clean Energy Future H.R. 4153
80% reductions in
Any source
The CES comes into effect 10
Through Innovation
power sector
with annual
years after enactment, or earlier
Act of 2021
emissions by 2050
carbon
if defined market penetration
intensity less
criteria are met for certain
than 0.82
technologies (e.g., coal-fired
metric tons
power plants with CCS).
carbon
dioxide per
megawatt-
hour
Clean Energy
H.R. 4309
100% by 2050
Renewables,
Targets set individual y for every
Innovation and
nuclear, CCS,
electric utility. Emissions
Deployment Act of
natural gas
reductions outside the power
2021
sector (e.g., electrified space
heating, electric vehicle charging,
direct air capture) covered by
the CES.
116th Congress
Climate Solutions
H.R. 330
100% by 2035
Renewables
Additional policy details not set
Act of 2019
in legislation; instead, to be
determined by DOE regulations.
Clean Energy
S. 1359 / H.R. 100% by 2050, or
Renewables,
Targets set individual y for every
Standard Act of
2597
potential y later for
nuclear, CCS,
electric utility up to 90% before
2019
some utilities
natural gas
2040, then increasing 1
percentage point each year after
utility reaches 90%.
Renewable
S. 1974
1.5 percentage
Renewables
Targets set individual y for every
Electricity Standard
points greater than
electric utility.
Act
2019 levels in 2020;
increasing by 2
percentage points
annual y for 2021-
2029 and by 2.5
percentage points
annual y for 2030-
2035
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Clean Energy Standards: Selected Issues for the 117th Congress

Bill
Eligible
Selected Distinguishing
Short Title
Number(s)
Final Target
Sources
Feature(s)
Clean Energy
H.R. 7516
100% by 2050
Renewables,
Targets set individual y for every
Innovation and
nuclear, CCS,
electric utility. Emissions
Deployment Act of
natural gas
reductions outside the power
2020
sector (e.g., electrified space
heating, electric vehicle charging,
direct air capture) covered by
the CES.
American
H.R. 9036
91% by 2039
Renewables
Program administered by the
Renewable Energy
Federal Energy Regulatory
and Efficiency Act
Commission (as opposed to
DOE)
Clean Energy Future H.R. 9054
80% reductions in
Any source
CES comes into effect 10 years
Through Innovation
power sector
with annual
after enactment, or earlier if
Act of 2020
emissions by 2050
carbon
defined market penetration
intensity less
criteria are met for certain
than 0.825
technologies (e.g., coal-fired
metric tons
power plants with CCS).
carbon
dioxide per
megawatt-
hour
Source: Prepared by CRS.
Notes: DOE = U.S. Department of Energy; CCS = fossil fuel-fired power plants equipped with carbon capture
and sequestration. Bil s for each Congress are listed in chronological order by date of introduction. Final target is
the maximum share of eligible clean energy sources to be used for electricity generation required by the CES,
and the year by which that share is to be met. Carbon intensity refers to the volume of greenhouse gases
released per unit of electricity generation. Bil s may have additional eligibility requirements for some sources
beyond those listed here (e.g., limitations on biomass sources, minimum carbon intensity requirements for
natural gas, consideration of upstream methane emissions for fossil fuels). Some bil s contain additional policy
provisions.
Other legislation introduced in the 117th and 116th Congresses would address energy sources for
electricity generation directly (e.g., fossil fuel bans, net-zero emissions target) or indirectly (e.g.,
tax incentives for certain sources), but these measures are not discussed in this report. This report
also does not discuss carbon pricing proposals, although they, too, could potential y affect the
share of electricity coming from different sources.10
Potential Considerations
A number of stakeholders—including the Biden Administration, some Members of Congress,
some climate change advocates, and some utilities—have voiced support for enacting a CES in
the 117th Congress, though with some disagreement over policy details.11 Among both policy

10 In carbon pricing proposals, policymakers attach a price to GHG emissions or the inputs that create them. A price on
emissions or emissions inputs—namely fossil fuels—would increase the relative price of the more carbon -intensive
energy sources. T his result is expected to spur innovation in less carbon-intensive technologies and stimulate other
behavior that may decrease emissions. A summary of carbon pricing bills is provided in CRS Report R45472, Market-
Based Greenhouse Gas Em ission Reduction Legislation: 108th Through 117th Congresses, by Jonathan L. Ramseur.
11 See example statements in Ben Geman, “Exclusive: T he Big Push for a Clean Power Mandate,” Axios, April 26,
2021; Miranda Willson, “Clean Electricity Standard: A Boost for Coal?,” E&E News, May 18, 2021; and Zack Budryk,
“More T han 75 Companies Ask Congress to Pass Clean Electricity Standard,” The Hill, July 7, 2021.
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supporters and opponents, several concerns and criticisms have been raised against a national
CES. To a certain extent, a CES can be designed to address these concerns. In some cases, efforts
to address any one concern could exacerbate others.
One consideration concerns nuclear power and carbon capture. Electricity generation using these
technologies general y receives policy support under most CES proposals, often at a level
comparable to electricity generation from renewable energy sources. Some environmental justice
advocates and others oppose policy support for these technologies for various reasons.12 For
example, the White House Environmental Justice Advisory Council included nuclear and CCS in
its list of “projects that wil not benefit a community.”13 A CES is widely viewed as being
supportive of nuclear power and carbon capture projects, in contrast with a renewable portfolio
standard (RPS) that supports renewable energy only. Some CES proposals attempt to address
environmental justice concerns, either by excluding nuclear and carbon capture or through other
provisions. For example, the American Renewable Energy Act of 2021 (H.R. 3959) would
establish an RPS that also includes a carve out aimed at incentivizing the development of
renewable energy projects in defined “environmental justice communities,” among others.
A second consideration is electricity affordability, a topic of long-standing interest to Congress
and one receiving particular attention during the COVID-19 pandemic.14 Many studies estimate a
CES would increase national average electricity prices compared with what they would be
without one. Table 2 summarizes cost estimates from studies of 100% clean energy standards or
clean energy standards with comparable goals.15 Some studies attempted to model specific policy
details from bil s listed in Table 1, while others model ed 100% CES policies in general. Given
the uncertainty in projecting power sector conditions in the future (even over the relatively short
period of 10-15 years), none of these studies individual y is likely to correctly project future
costs. However, the range of cost estimates in these studies is likely a good indicator of the range
of outcomes should a 100% CES policy be enacted, assuming policy details are general y similar
to those assumed in these studies.16

12 See discussion and points of view summarized in, for example, Letter from Center for Biological Diversity et al. to
Sen. Chuck Schumer, Majority Leader, Rep. Nancy Pelosi, Speaker of the House, Sen. Joe Manchin, Chairman of the
Energy & Natural Resources Committee, and Rep. Frank Pallone, Chairman of the Energy & Commerce Committee,
May 12, 2021, at https://www.biologicaldiversity.org/programs/energy-justice/pdfs/2021-5-12_600-Group-Letter-for-
RES.pdf; U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate
Change, The CLEAN Future Act and Environm ental Justice: Protecting Frontline Com m unities, 117th Cong., 1st sess.,
April 15, 2021; and Anthony Adragna, “Democrats’ Next Big Fight: What Exactly Is Clean Energy?,” Politico, April
30, 2021.
13 White House Environmental Justice Advisory Council, Final Recommendations: Justice40, Climate and Economic
Justice Screening Tool and Executive Order 12898 Revisions, May 21, 2021, p. 59.
14 For example, many states implemented moratoria on service disconnections for nonpayment (i.e., shut -offs) in 2020
so that individuals could maintain access to electricity during stay -at-home orders. For further discussion, see CRS
Report R46401, COVID-19 Electric Utility Disconnections, by Richard J. Campbell and Ashley J. Lawson .
15 One group modelled an 80% clean by 2030 standard on the grounds that “t he Biden administration goal of 100
percent clean power by 2035 implies an interim goal of at least 80 percent by 2030 .” Mike O’Boyle et al., A National
Clean Electricity Standard to Benefit All Am ericans, Energy Innovation, April 2021, p. 1. Some modelling groups
identified in Table 2 are collaborations among researchers from several organizations (e.g., the Clean Energy Futures
Project). Media and other reports of these studies may refer to them by different names, such as o ne member of the
group. Table 2 excludes studies that looked at decarbonization in general but not a CES specifically.
16 T he range of cost estimates in Table 2 probably do not reflect likely outcomes of the proposed CEPP, because that
policy is expected to shift costs from electricity customers to federal taxpayers, relative to a CES. Lindsey Walter,
Don’t Call It a Standard: What’s Unique About the Clean Electricity Payment Program (CEPP) , T hird Way, August
12, 2021.
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Table 2. Cost and Benefit Estimates for 100% Clean Energy Standards
Policy Costs,
Policy Benefits,
Relative to
Relative to
Modelling Group
Policy Details
Business-as-Usual
Business-as-Usual
Notes
Resources for the
77% clean in 2035
$106 bil ion
$470 bil ion in
Reported costs and
Future
increase in
reduced climate
benefits are the net
electricity costs;
change impacts;
present value of
$29 bil ion
$226 bil ion in
cumulative 2020-
increased federal
reduced premature
2035 costs and
expenditure for
deaths (due to
benefits.
increased use of
lower levels of co-
energy tax credits
pol utants); $19
bil ion in increased
utility profits
Electric Power
100% clean by 2050
50% increase in
not calculated
Study also reports
Research Institute
national average
changes in
annual wholesale
wholesale electricity
electricity price in
prices by region.
2050
Alternative
scenarios model a
100% by 2035 CES
and variations on
policy design
elements (e.g., point
of regulation,
alternative
compliance
payment).
FTI Consulting
80% clean by 2030
0.25% reduction in
not calculated
Costs reported as
and 100% clean by
2031-2035 average
net GDP impacts,
2035
national GDP
including, for
example, economic
benefits associated
with increased
investment in
electricity
infrastructure. Study
also reports impacts
in earlier years and
by region.
National Bureau of
100% clean by 2035
$1-$4/MWh
not calculated
Study also reports
Economic Research
increase in national
electricity price
average wholesale
changes by state.
electricity price in
2035
Goldman School of
80% clean by 2030
6% increase in
$1.7 tril ion in
Policy scenario also
Public Policy,
national average
reduced climate
includes increased
GridLab, Energy
wholesale electricity
change and health
electrification of
Innovation
costs in 2030
impacts (from
end uses (e.g.,
power sector
transportation).
reductions only)
Study also reports
cost estimates with
health and
environmental
externalities
included.
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Policy Costs,
Policy Benefits,
Relative to
Relative to
Modelling Group
Policy Details
Business-as-Usual
Business-as-Usual
Notes
American Action
100% clean by 2035
$1.8-$2.13 tril ion
not calculated
Costs are for
Forum
cumulatively, 2021-
generation assets
2035
only. Study also
reports changes in
customer utility
bil s.
Clean Energy
100% clean by 2040
$342 bil ion
$637 bil ion in
Costs and benefits
Futures Project
reduced climate
are reported as net
change impacts;
present value of
$1.13 tril ion in
cumulative benefits
health impacts
2020-2050. Study
also reports air
quality
improvements by
county.
Natural Resources
80% clean by 2030
$17-$22 bil ion
$97-$184 bil ion in
Net present value
Defense Council
or 100% clean by
annual y, on
2030
of costs and
and Environmental
2035 (study does
average, through
benefits are
Defense Fund
not report results
2030
reported as the
for individual
range over multiple
scenarios)
scenarios. Some
scenarios include
additional policies,
such as tax credit
extensions. At least
one scenario
models a Clean
Electricity Payment
Program.
Sources: Resources for the Future, “Projected Effects of the Clean Energy Standard Act of 2019,” May 2019, at
https://www.rff.org/publications/issue-briefs/projected-effects-clean-energy-standard-act-2019/; Electric Power
Research Institute, “Analyzing Federal 100% Clean Energy Standards,” February 2021, at https://www.epri.com/
research/products/000000003002020121; FTI Consulting, “Power Market and Economic Impacts of a U.S. Clean
Energy Standard,” March 2021, at https://www.remi.com/event/scott-nystrom-power-ma rket s-and-economic-
impacts-of-a-u-s-clean-energy-standard-ces/; National Bureau of Economic Research, “Robust Decarbonization of
the U.S. Power Sector: Policy Options,” April 2021, at https://www.nber.org/papers/w28677; Goldman School of
Public Policy, GridLab, and Energy Innovation, “2030 Report: Powering America’s Clean Economy,” April 2021,
at https://energyinnovation.org/wp-content/uploads/2021/04/2030-Report.pdf; American Action Forum, “The
Cost of Clean Generation,” June 2021, at https://www.americanactionforum.org/research/the-cost-of-clean-
generation/; Clean Energy Futures, “An 80x30 Clean Electricity Standard: Carbon, Costs, and Health Benefits,”
July 2021, at https://cleanenergyfutures.syr.edu/; Natural Resources Defense Council and Environmental Defense
Fund, “80% Clean Power by 2030: Achievable With Massive Benefits,” August 2021, at https://www.nrdc.org/
experts/arjun-krishnaswami/80-clean-power-2030-achievable-massive-benefits.
Notes: Some studies model ed policies other than 100% CES, but the model ers identified those policies as
being comparable in stringency. Differences among studies include assumptions about business-as-usual
conditions; the makeup of clean energy sources used to satisfy policy requirements; cost metrics; policy details;
and the levels of greenhouse gas emission reductions. As a result, individual studies cannot necessarily be
compared with each other. For simplicity, this table shows total national electricity system costs, or the nearest
comparable cost estimate provided. Some studies estimated costs for different geographic scope (e.g., by state)
or for a different metric (e.g., customer bil s). The Notes column lists other reported cost estimates as a
research aid.
A third consideration is electricity reliability, another issue of long-standing interest to Congress.
Blackouts following extreme weather events in 2020 and 2021 reignited debate about whether
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changing energy sources for electricity generation (i.e., increased use of wind and solar energy,
decreased use of coal) pose threats to reliability.17 For example, a House committee held a hearing
on the days-long power outages that affected much of Texas in February 2021, and issues of
electric reliability and changing energy sources were discussed.18 Some stakeholders see inclusion
of natural gas in a CES as a way to ensure reliability.19 Another option is to exclude from
compliance calculations any emissions from power plants that are required for reliability
purposes. The CLEAN Future Act (H.R. 1512, as introduced), for example, includes both these
provisions.20
Putting a 100% Target in Context
Current Clean Energy Use
As summarized above, most recent CES proposals would require nearly al electricity to come
from eligible clean energy sources in the 2035-2050 timeframe. The distinction between “al ” and
“nearly al ” arises from the policy details provided in some of the proposals. A 100% target does
not necessarily require 100% of electricity to come from eligible clean sources. For example, a
CES might exempt electricity sales from smal utilities or al ow alternative compliance
payments.21 The actual amount of clean energy used would be affected by utility compliance
choices, future technology costs, and other factors.
How much clean energy was used in the U.S. electricity sector in 2020? The answer depends
upon what sources are considered to be clean, as shown in Figure 1 and discussed in the
following paragraphs. In 2020, renewable energy fueled 21% of U.S. electricity, while renewable
energy plus nuclear power fueled 40%.22 These sources together with natural gas fueled 80% of
U.S. electricity in 2020.

17 Wind and solar energy have different operational characteristics than conventional ener gy sources (e.g., coal, natural
gas, nuclear power), and they are variable in nature. Because the electricity grid was primarily designed to
accommodate conventional sources that can be called upon as needed (barring extreme events or regular maintenance
requirements), some system design and operational changes may be required to integrate large amounts of wind and
solar energy. For a discussion of these issues and potential solutions, see CRS In Focus IF11257, Variable Renewable
Energy: An Introduction, by Ashley J. Lawson.
18 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Oversight and Investigations, Power
Struggle: Exam ining the 2021 Texas Grid Failure, 117th Cong., 1st sess., March 24, 2021. Most experts do not identify
changing energy sources as a main contributor to the T exas outages, though some observers see the two issues as being
connected. For further discussion, see CRS Insight IN11608, Power Outages in Texas, by Richard J. Campbell.
19 See, for example, Molly Christian and Zack Hale, “Gas T reatment, Infrastructure T ensions Hamper Clean Electricity
Standard Efforts,” S&P Global Market Intelligence, June 10, 2021.
20 T he CLEAN Future Act would set an emissions intensity threshold for eligibility, including greenhouse gas (GHG)
emissions associated with fuel production and transport. Some natural gas-fired generators meet the eligibility
threshold when considering onsite emissions. It is unclear how many such generators would be eligible after accounting
for upstream emissions because the determination would be made pursuant to a to -be-determined U.S. Environmental
Protection Agency standard. See the CLEAN Future Act, §204(d).
21 T he point of regulation can also affect the extent to which a 100% target requires 100% of electricity to come from
eligible sources. Regulating load serving entities (typically, distribution utilities), as is frequently the case, can leave
“headroom” under the policy due to losses associated with electricity transmission and distribution. See discussion in
Electric Power Research Institute, “Analyzing Federal 100% Clean Energy Standards,” February 2021, available at
https://www.epri.com/research/products/000000003002020121.
22 U.S. Energy Information Administration (EIA), Monthly Energy Review, T able 7.2a and T able 10.6, July 2021.
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Figure 1. 2020 U.S. Electricity Generation by Source Type

Source: U.S. Energy Information Administration, Monthly Energy Review, “Table 7.2a. Electricity Net Generation:
Total (Al Sectors)” and “Table 10.6. Solar Electricity Net Generation.”
Notes: Other includes petroleum and gases derived from fossil fuels. Details of energy source classification are
provided in this report and in the EIA source.
Figure 1 uses the following classifications. Renewable energy means al renewable energy
sources, including smal -scale and distributed sources (e.g., rooftop solar), al hydropower, and al
biomass. Some introduced CES bil s would limit the eligibility of hydropower and biomass, for
example by specifying types of eligible biomass feedstocks, but those limitations are not
considered here. Natural gas means any power plant using primarily natural gas, regardless of
technology type or carbon intensity. Some bil s would al ow natural gas plants to be eligible if
they met certain carbon intensity thresholds, but those limitations are not considered here. Should
Congress debate a national CES, it could set eligibility criteria based on energy source, carbon
intensity, or other characteristics.

State Targets and Utility Commitments
As noted above, eleven states plus the District of Columbia have enacted legislation to achieve
carbon-free electricity generation, and at least eight additional states have goals or executive
orders targeting carbon-free electricity generation. Beyond these state requirements, some electric
companies have made voluntary commitments to reduce GHG emissions from their electricity
generation.23

23 T hese utility decarbonization goals vary in st ringency, scope, and final target date. T he most stringent
decarbonization goal is for 100% carbon-free electricity, also referred to as carbon neutral, net zero, or 100% clean.
Different terms for decarbonization are sometimes used interchangeably, though they can imply different
implementation options. For example, 100% carbon -free generally means all generation sources will be carbon -free,
while carbon neutral and net zero potentially leave open the possibility of offsetting some emissions with reduction s
outside the utility’s generation supply (e.g., retirement of renewable energy credits [RECs] from other states). Many
decarbonization target dates are between 2040 and 2050, outside the typical planning horizon for utilities. As a result,
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Combined, these state targets and utility commitments cover 77% of U.S. electricity sales.24 The
most stringent of these commitments—the carbon-free state targets and the utility commitments
of at least an 80% reduction in GHG emissions—cover 69% of U.S. electricity sales.25
Outlook for Clean Energy in the U.S. Electricity System
The possible future makeup of the U.S. electricity system might affect (among other things)
congressional perceptions related to the necessity or feasibility of a CES. Estimating the future
energy system makeup typical y is chal enging, especial y over multi-decadal periods. The
COVID-19 pandemic and other factors make such outlooks especial y chal enging.
One prominent estimate of future changes in the U.S. energy system is made each year by the
U.S. Energy Information Administration (EIA) in its Annual Energy Outlook (AEO).26 The AEO
accounts for most federal and state energy policies (e.g., state CES policies) in place at the time
of its preparation. In February 2021, EIA released its first long-term projections accounting for
the pandemic. In EIA’s assessment, the pandemic’s impacts on the electricity sector wil be
mostly felt in the next few years. After that, long-term sectoral trends return to dominance: “EIA
does not project long-term structural changes in electricity demand resulting from the pandemic,
and the AEO2021 Reference case projects that demand largely returns to 2019 levels by 2025.”27
In EIA’s 2021 projections, the share of total U.S. electricity generation coming from renewable
sources in 2050 varies from 33% to 57%, depending on factors such as future energy prices and
economic growth. The share from nonemitting sources (i.e., renewables and nuclear) in 2050
varied from 44% to 67% in the projections, and the share from nonemitting sources together with
natural gas varied from 86% to 93%.28 Figure 2 compares EIA’s 2021 projections for the share of

many decarbonization targets—regardless of what they are called—do not have associated implementation plans.
Because of this uncertainty, it is difficult to assess meaningful differences among terms.
24 T otal electricity sales reported by the EIA. T he most recent annual data available are for 2019. CRS estimated the
share of total U.S. electricity sales covered by a utility commitment by compiling lists of companies with a
commitment from three sources: Smart Electric Power Alliance (SEPA), “Utility Carbon Reduction T racke r,” accessed
August 23, 2021, at https://sepapower.org/utility-transformation-challenge/utility-carbon-reduction-tracker/; Clean Air
T ask Force (CAT F), “ State and Utility Decarbonization Commitments,” October 1, 2020; and Jeffrey Ryser, “ Utility
Emissions, Renewables Goals Accelerate, But Coal Retirements May Be T oo Slow,” S&P Global, February 25, 2021.
In some cases, the names of companies provided by SEPA, CAT F, or S&P Global do not match the utility names in the
EIA dataset. In these cases, CRS identified corresponding utilities (an exact name match was required to analyze the
EIA data) using utility websites and other public documents. Some identified utilities are also covered by a state target.
Sales from these utilities were counted once in the final estimate.
25 For this analysis, CRS assessed utility target stringency based on its characterization by SEPA, CAT F, and S&P
Global. CRS did not independently verify utility targets. Most identified utility targets are based on an absolute (i.e.,
mass-based) reduction in GHG emissions. For example, a utility might target a 90% reduction in carbon dioxide
emissions from 2005 levels by 2050. Some targets are based on relative (i.e., intensity-based) reduction in GHG
emissions. In theory, intensity-based reduction targets can be achieved without a reduction in absolute emissions.
Estimating future GHG emissions is beyond the scope of this analysis, so n o attempt was made to “ convert” intensity-
based targets into absolute targets. For example, a utility might target a 70% reduction in GHG intensity from 2005
levels by 2040. For purposes of estimating the share of electricity sales covered by commitments, that target is treated
the same as a 70% mass-based reduction target.
26 For an overview of the Annual Energy Outlook, see CRS In Focus IF11691, The Annual Energy Outlook (AEO): A
Brief Overview, by Ashley J. Lawson and Kelsi Bracmort .
27 EIA, Annual Energy Outlook 2021 Narrative, February 2021, p. 12, https://www.eia.gov/outlooks/aeo/pdf/
AEO_Narrative_2021.pdf.
28 CRS calculations based on data from EIA, Annual Energy Outlook 2021, February 3, 2021. EIA’s projections do not
include projections for CCS.
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total U.S. electricity generation coming from these different source types. The classifications in
Figure 2 match those in Figure 1, and are used to provide context.
Figure 2. Projected Share of Total U.S. Electricity Generation, by Source Type

Source: CRS calculations based on data from EIA, Annual Energy Outlook 2021, February 3, 2021.
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Notes: Details of energy source classification are provided in this report and in the EIA source. EIA side cases
include alternative assumptions about future energy supply and prices, technology costs, and economic growth.

Concluding Observations
Congressional debate on options to reduce GHG emissions is ongoing, including consideration of
a CES. Other issues being debated by the 117th Congress, such as infrastructure, could also affect
future GHG emissions from the power sector. For example, non-CES legislation could influence
power plant developers’ choice about energy sources by altering their relative prices in the market
(e.g., tax incentives to lower prices for certain sources or carbon pricing to increase prices for
certain sources). Legislation also could affect electricity demand by increasing use of electricity
in the economy (e.g., for transportation) or decreasing electricity demand by promoting efficiency
measures. Legislation not directly targeted at the electricity system also could affect the outlook
for clean energy in the U.S. electricity system. For example, legislation affecting overal
economic activity could affect future electricity demand, and infrastructure policy could influence
the private sector’s decisions about what energy sources to use for electricity generation. Also,
noncongressional actions (e.g., executive actions, state policies) affect the U.S. electricity system.
For example, the Federal Energy Regulatory Commission initiated a rulemaking process in July
2021 aimed at “improv[ing] transmission planning and cost al ocation and generator
interconnection processes as the nation transitions to a cleaner energy future.”29
In short, numerous policies the 117th Congress might consider (and noncongressional actions as
wel ) could affect the future makeup of the U.S. electricity system. Should Congress also choose
to debate a CES, the interactions among some or al of these factors might be relevant.

Author Information

Ashley J. Lawson

Analyst in Energy Policy

Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan
shared staff to congressional committees and Members of Congress. It operates solely at the behest of and
under the direction of Congress. Information in a CRS Report should n ot be relied upon for purposes other
than public understanding of information that has been provided by CRS to Members of Congress in
connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not
subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in
its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or
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copy or otherwise use copyrighted material.

29 Federal Energy Regulatory Commission, “ News Release: FERC Begins Reform Process to Build the T ransmission
System of the Future,” July 15, 2021.
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