Clean Energy Standards: Selected Issues for the March 26, 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.
Members of Congress have demonstrated a longstanding interest in CES policies, with proposals for a national CES dating at
least to 1997. None has been enacted. Most recently, seven bills introduced in the 116th Congress would have established a
national CES (sometimes in conjunction with other policies). The measures differed in eligible sources, final targets, and
implementation details. For example, one bill would have required 100% of covered electricity sales to come from renewable
energy sources by 2035. Another measure would have established CES targets consistent with 80% reductions in electricity
GHG emissions. Four of the bills would have established a 100% clean energy requirement for U.S. electricity generation
with target dates ranging from 2035 to 2050.
Other proposals put forward in 2020 also might be relevant to CES discussions in the 117th Congress. Two separate House
committees supported 100% CES policies. One aimed to achieve 100% clean energy used for electricity generation by 2050
and the other aimed for 100% by 2040. Additionally, President Biden campaigned on a goal of 100% clean energy used for
electricity generation by 2035, and an executive order issued in January 2021 reiterates that goal.
For context, renewable sources made up 18% of U.S. electricity generation in 2019, nuclear power made up 20%, natural gas
made up 38%, and coal (without CCS) made up 24%. 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 non-emitting sources (i.e.,
renewables and nuclear) in 2050 varied from 44% to 67% in the projections, and the share from non-emitting sources
together with natural gas varied from 86% to 93%.
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). The ongoing coronavirus disease 2019 (COVID-19) pandemic makes such
outlooks especially challenging, because of the impact the pandemic is having on U.S. energy consumption and production.
Another complicating factor is the possibility that the 117th Congress could change U.S. energy policy (not including
consideration of a CES). For example, legislation might aim to change the relative price of certain energy sources through tax
incentives, carbon pricing, or other means. Legislation could seek to alter future U.S. electricity demand, for example with
policies to increase electricity use for transportation or, alternatively, policies to decrease electricity use through improved
efficiency. Legislation not directly targeting the U.S. electricity system also could be relevant, for example legislation
directed towards affecting overall economic activity or infrastructure. Finally, non-congressional action such as executive
actions or state policies also could affect the U.S. electricity system.
In short, numerous policies the 117th Congress might consider could affect the future makeup of the U.S. electricity system,
as could non-congressional actions. The interactions among some or all of these factors might be relevant, should Congress
choose to debate a CES.
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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 called 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
Congressional and constituent interest in this policy continues in the 117th Congress.
As of 2020, thirty states and the District of Columbia have a CES.2 Of these, 10 ultimately will
require all covered electricity sales to come from eligible clean energy sources. The 10
jurisdictions are California, Colorado, the District of Columbia, Hawaii, Massachusetts, New
Jersey, New Mexico, New York, Virginia, and Washington.3 Additionally, five states have non-
binding goals of 100% covered electricity sales from eligible clean energy sources: Connecticut,
Maine, Nevada, Rhode Island, and Wisconsin.
This report provides two analyses to inform potential CES policy discussions in the 117th
Congress. First, this report summarizes CES proposals from the 116th Congress. Second, this
report analyzes the current and potential future makeup of the U.S. electricity system, for context.
Bills Introduced in the 116th Congress
CRS identified seven bills introduced in the 116th Congress that would have established a national
clean energy standard.4 Table 1 summarizes the CES proposals identified in these seven bills,
focusing on two key policy features: the final target and eligible sources. The final target is
typically 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

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 non-renewable 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 116th Congress. For more information about CES, see CRS Report R45913,
Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations, by Ashley J. Lawson.
2 Some of these states have an RPS in place, setting goals for renewable energy use only. Three U.S. territories also
have an RPS. Eight additional states and one additional territory have voluntary renewable portfolio goals in place.
N.C. Clean Energy Technology Center Database of State Incentives for Renewables & Efficiency (DSIRE), Renewable
Portfolio Standards and Clean Energy Standards, September 2020.
3 The District of Columbia, Hawaii, Massachusetts, and Virginia each require 100% of covered electricity sales to come
from renewable energy sources. The dates for achieving those targets vary. In 2020, Arizona regulators approved a
100% CES, but the policy is not yet finalized.
4 Bills were identified by searching Congress.gov using the phrases “clean energy,” “clean energy standard,”
“renewable electricity standard,” “renewable energy,” “renewable energy standard,” 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

policies and past legislative proposals applied across all utilities; however, several bills in the
116th Congress would have set targets for each utility individually. This distinction is noted in the
table. Eligible sources are the sources that may be used for compliance with the CES. Bills in the
116th Congress 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).
Table 1. National Clean Energy Standard (CES) Legislative Proposals
in the 116th Congress
Selected
Distinguishing
Short Title
Bill Number(s)
Final Target
Eligible Sources
Feature(s)
Climate Solutions
H.R. 330
100% by 2035
Renewables
Additional policy
Act of 2019
details not set in
legislation; instead,
to be determined by
DOE regulations.
Clean Energy
S. 1359 / H.R. 2597
100% by 2050, or
Renewables,
Targets set
Standard Act of
potentially later for
nuclear, CCS,
individually for
2019
some utilities
natural gas
every electric utility
up to 90% before
2040, then
increasing 1
percentage point
each year after
utility reaches 90%.
Renewable
S. 1974
1.5 percentage
Renewables
Targets set
Electricity Standard
points greater than
individually for
Act
2019 levels in 2020;
every electric utility.
increasing by 2
percentage points
annually for 2021-
2029 and by 2.5
percentage points
annually for 2030-
2035
Clean Energy
H.R. 7516
100% by 2050
Renewables,
Targets set
Innovation and
nuclear, CCS,
individually for
Deployment Act of
natural gas
every electric utility.
2020
Emissions
reductions outside
the power 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
Renewable Energy
administered by the
and Efficiency Act
Federal Energy
Regulatory
Commission (as
opposed to DOE)
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Selected
Distinguishing
Short Title
Bill Number(s)
Final Target
Eligible Sources
Feature(s)
Clean Energy Future H.R. 9054
Target set to
Any source with
CES comes into
Through Innovation
achieve 80%
annual carbon
effect 10 years after
Act of 2020
reductions in power intensity less than
enactment, or
sector emissions by
0.825 metric tons
earlier if defined
2050
carbon dioxide per
market penetration
megawatt-hour
criteria are met for
certain technologies
(e.g., coal-fired
power plants with
CCS).
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 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 (e.g., limitations on
biomass sources, minimum carbon intensity requirements for natural gas). Some bil s contain additional policy
provisions.
Other legislation introduced in the 116th Congress would have addressed 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 potentially affect the
share of electricity coming from different sources.5
Other Proposals
Several other CES proposals were released during the 116th Congress.6 Generally, these had fewer
specific policy details compared to the introduced bills. Unlike some introduced bills, none of
these other CES proposals call for 100% renewable energy.
On January 28, 2020, majority leaders of the House Committee on Energy and Commerce
released draft legislative text of the Climate Leadership and Environmental Action for our
Nation’s Future Act (the CLEAN Future Act). Its sponsors describe the CLEAN Future Act as “a
comprehensive proposal of sector-specific and economy-wide solutions to address the climate

5 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. This 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 Emission Reduction Legislation: 108th Through 116th Congresses, by Jonathan L. Ramseur.
6 In addition to the other proposals discussed in this report, the Senate Democrats’ Special Committee on the Climate
Crisis released a report, The Case for Climate Action: Building a Clean Economy for the American People. The report
identified a CES as a policy that “could guarantee the electric sector’s contribution to meeting the global target of net-
zero by no later than 2050,” but the report did not make a specific recommendation or proposal for a CES. Senate
Democrats’ Special Committee on the Climate Crisis, The Case for Climate Action: Building a Clean Economy for the
American People, August 2020, p. 20.
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crisis.”7 Among the provisions in the CLEAN Future Act is a CES with a final target of 100% by
2050.8
On June 30, 2020, Democrats on the House Select Committee on the Climate Crisis released a
majority staff report, Solving the Climate Crisis: The Congressional Action Plan for a Clean
Energy Economy and a Healthy, Resilient, and Just America. The report aims to “[lay] out the
Climate Crisis Action Plan, full of detailed, ambitious and actionable climate solutions that
Congress should enact to benefit American families in communities across the nation.”9 Among
the recommendations in the report is that Congress should enact a CES with a final target of
100% by 2040.10
Outside of Congress, President Biden supported a goal of “a carbon pollution-free power sector
by 2035” in his campaign, and has continued to support that goal in his administration. For
example, an executive order issued January 27, 2021, aims to use federal procurement authorities
to “achieve or facilitate a carbon pollution-free electricity sector no later than 2035.”11
Putting a 100% Target in Context
As summarized above, most CES proposals in the 116th Congress would have required nearly all
electricity to come from eligible clean energy sources in the 2035-2050 timeframe. The
distinction between “all” and “nearly all” 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 small utilities or allow
alternative compliance payments. The actual amount of clean energy used would be affected by
utility compliance choices, future technology costs, and other factors.
The U.S. electricity system is large and complex, and many power plants and associated
infrastructure have lifetimes of 40 years or more. Experts disagree about the extent to which these
features present cost and feasibility challenges to achieving a 100% CES in three decades or less.
Much of the debate focuses on wind and solar energy because of their unique operating
characteristics.12 Assessing the cost and feasibility of a 100% CES is beyond the scope of this
report. However, this section provides some relevant data and discussion to put a 100% CES
target in context.

7 House Committee on Energy and Commerce, “E&C Leaders Release Draft CLEAN Future Act Legislative Text to
Achieve a 100 Percent Clean Economy,” press release, January 28, 2020, https://energycommerce.house.gov/
newsroom/press-releases/ec-leaders-release-draft-clean-future-act-legislative-text-to-achieve-a-100.
8 Title II-Power, Subtitle A-Federal Clean Electricity Standard, CLEAN Future Act discussion draft,
https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/
0128%20CLEAN%20Future%20Discussion%20Draft.pdf.
9 House Select Committee on the Climate Crisis, “Select Committee Democrats Release ‘Solving the Climate Crisis,’ a
Congressional Roadmap for Ambitious Climate Action,” press release, June 30, 2020, https://climatecrisis.house.gov/
news/press-releases/climate-plan-press-release.
10 Solving the Climate Crisis: The Congressional Action Plan for a Clean Energy Economy and a Healthy, Resilient,
and Just America, p. 4, https://climatecrisis.house.gov/sites/climatecrisis.house.gov/files/
Climate%20Crisis%20Action%20Plan.pdf.
11 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.
12 For more information on issues associated with using high levels of wind and solar, see CRS In Focus IF11257,
Variable Renewable Energy: An Introduction, by Ashley J. Lawson, and CRS Insight IN11065, An Electric Grid Based
on 100% Renewable Energy?, by Richard J. Campbell.
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How much clean energy was used in the U.S. electricity sector in 2019? The answer depends
upon what sources are considered to be clean, as shown in Figure 1 and discussed in the
following paragraphs. In 2019, renewable energy fueled 18% of U.S. electricity, while renewable
energy plus nuclear power fueled 38%.13 These sources together with natural gas fueled 76% of
U.S. electricity in 2019.
Figure 1. 2019 U.S. Electricity Generation by Source Type

Source: U.S. Energy Information Administration, Electric Power Monthly, “Table 1.1. Net Generation by Energy
Source: Total (Al Sectors).”
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 all renewable energy
sources, including small-scale and distributed sources (e.g., rooftop solar), all hydropower, and all
biomass. Some CES bills introduced in the 116th Congress 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 CES bills introduced in the
116th Congress would allow 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.

13 This estimate does not include the 3,959,824 megawatt-hours (MWh) generated in 2019 by Unit 8 of the W.A. Parish
power plant in Texas, widely known as Petra Nova. That unit is equipped with carbon capture and sequestration (CCS)
capable of sequestering about 33% of the unit’s carbon dioxide (CO2) emissions. Petra Nova’s output was 0.1% of total
U.S. electricity generation in 2019. For readability, the main body of this report rounds values to zero decimal places
and does not identify Petra Nova’s generation. Petra Nova’s operators shut down the CCS equipment in 2020, citing
impacts of the COVID-19 pandemic. Generation data is from U.S. Energy Information Administration (EIA), Form
EIA-923, https://www.eia.gov/electricity/data/eia923/. Additional information about Petra Nova comes from EIA,
Petra Nova Is One of Two Carbon Capture and Sequestration Power Plants in the World, October 31, 2017.
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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 typically is challenging, especially over multi-decadal periods. The
COVID-19 pandemic and other factors make such outlooks especially challenging.
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).14 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 will 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.”15
In EIA’s 2021 projections, the share of total U.S. electricity generation coming from renewable
sources in 2050 varied from 33% to 57%, depending on factors such as future energy prices and
economic growth. The share from non-emitting sources (i.e., renewables and nuclear) in 2050
varied from 44% to 67% in the projections, and the share from non-emitting sources together with
natural gas varied from 86% to 93%.16 Figure 2 compares EIA’s 2021 projections for the share of
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.

14 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.
15 EIA, Annual Energy Outlook 2021 Narrative, February 2021, p. 12, https://www.eia.gov/outlooks/aeo/pdf/
AEO_Narrative_2021.pdf.
16 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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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.
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.

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It is unknown how the COVID-19 pandemic ultimately will affect clean energy’s trajectory,
because the pandemic is ongoing and the economic impacts could still change. In any case, two
key factors affecting the share of clean energy in the future U.S. electricity system are (1) the
pace of additions of new clean energy, and (2) total electricity demand.17 Legislative responses to
the pandemic or other issues such as climate change could affect either or both of these factors,
increasing the uncertainty in long-term projections.
The pace of clean energy additions is affected by the pace of new power plant construction
overall, and the share of clean energy within new power plants. New power plants are planned
when needed to meet increasing electricity demand, but demand in the United States overall was
mostly unchanged from 2005 to 2019.18 Generally, electricity demand increases with increasing
population and economic activity, though energy efficiency and conservation can offset these
factors. New power plants also are planned to replace retired power plants as part of the natural
aging and turnover of the U.S. power plant fleet.
While a number of factors affect the share of clean energy within new power plant additions,
technology and fuel costs are two main drivers. Power plant developers generally choose an
energy source primarily based on economics. In other words, the sources that usually are used by
new power plants are the ones that can generate electricity at the lowest cost per unit of
electricity, inclusive of tax incentives or other financial factors. Policies, like state CES
requirements, also can influence decisions about new power plants. Economics and policy have
been favorable for new power plants using wind and solar energy for several years, and most
experts expect that will continue. For example, wind and solar are expected to make up 70% of
new capacity additions in 2021.19
Currently, when overall demand for electricity decreases, the share of clean energy goes up, all
else being equal. This outcome is driven mostly by wind and solar energy. Those sources have
relatively low operating costs (because the “fuel” is free), so they typically are used to generate
electricity whenever the wind is blowing and the sun is shining. In other words, once a power
plant using wind or solar is built, it often operates to the maximum extent possible, for economic
reasons. Decreases in electricity demand disproportionately affect non-renewable sources (e.g.,
coal) because of their relatively higher operating costs. These economic factors are part of the
reason why generation from coal-fired power plants fell in 2020.20
As noted above, Congress could enact non-CES legislation that could affect the pace of additions
of new clean energy, total electricity demand, or both. For example, legislation could influence
power plant developers’ choice about energy sources by altering their relative prices in the market

17 Retirement of existing clean energy power plants is another factor, mostly for nuclear power plants. For more
information, see CRS Report R42853, Nuclear Energy: Overview of Congressional Issues, by Mark Holt. The relative
share of different energy sources used for electricity additionally might be affected by other factors such as state
policies, but those are not discussed in this report.
18 From 2005 to 2019, total annual U.S. electricity generation was 4.1 trillion kilowatt-hours (kWh) on average, with a
high of 4.2 trillion kWh in 2018 and a low of 4.0 trillion kWh in 2009. EIA, Electricity Data Browser. Despite national
trends, some regions of the country may be experiencing electricity demand growth and a corresponding higher
buildout of new power plants.
19 EIA, Renewables Account for Most New U.S. Electricity Generating Capacity in 2021, January 11, 2021,
https://www.eia.gov/todayinenergy/detail.php?id=46416.
20 According to EIA, total U.S. electricity consumption fell an estimated 4% in 2020, compared to 2019 levels. At the
same time, the share of generation from coal fell from 24% in 2019 to an estimated 20% in 2020. In contrast, the share
of generation from natural gas and renewables increased from 2019 to 2020. EIA, Short-Term Energy Outlook,
December 2020, https://www.eia.gov/outlooks/steo/archives/dec20.pdf.
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(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
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Clean Energy Standards: Selected Issues for the 117th Congress

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 overall
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,
non-congressional actions (e.g., executive actions, state policies) affect the U.S. electricity
system. In short, numerous policies the 117th Congress might consider (and non-congressional
actions as well) could affect the future makeup of the U.S. electricity system. Should Congress
also choose to debate a CES, the interactions among some or all 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
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under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other
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