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Updated February 24, 2021
A Brief History of U.S. Electricity Portfolio Standard Proposals
Electricity portfolio standards are designed to change the
Some proposals include hydropower in their definition of
set of energy sources used to generate electricity, usually by
renewable sources, albeit often with restrictions based on
establishing requirements on utilities to procure a
size or age, while other proposals exclude hydropower in
percentage of electricity from specified eligible sources.
favor of non-hydro renewables. Many of the proposals
Since the 105th Congress, 76 proposals for a national
identified by CRS (42) took an intermediate approach,
portfolio standard have been introduced, but none has
exempting hydropower from the compliance requirement.
become law. This analysis provides historical context on
In general, sources that are exempted from a portfolio
federal portfolio standard proposals.
standard requirement could receive indirect financial
support. The level of support for exempted sources would
Previous Federal Proposals
likely be less than the support for eligible sources, but more
CRS sought to assemble a comprehensive list of federal
than the support for ineligible sources. Some proposals also
portfolio standard proposals through a search in
exempted other sources in addition to hydropower such as A full description of the search methodology
municipal solid waste (24 proposals) and new nuclear
and the list of previous legislation is available in CRS
power plants (5 proposals).
Report R45913, Electricity Portfolio Standards:
Background, Design Elements, and Policy Considerations
Figure 1 categorizes bills according to the types of sources
that would be eligible. All bills included some non-hydro
Of the proposals CRS identified, the earliest bill was
renewables, though there were differences about eligibility
introduced in 1997 in the 105th Congress. Some proposals
for some types of sources, especially biomass. The
were stand-alone; in other words, a national portfolio
introduced bills that only included non-hydro renewables
standard was the only provision in the bill. Other proposals
are represented by blue bars in the figure. Five bills defined
included a portfolio standard alongside other provisions.
eligible sources as “renewable sources” without further
clarification. These also are represented by the blue bars.
As Figure 1 shows, the number of introduced bills was
The majority of bills explicitly included some hydropower
highest in the 110th Congress. The 115th Congress saw the
for eligibility in addition to non-hydro renewables (red
fewest number of introduced bills of any Congress in which
bars), though some of these had age or size restrictions. The
a portfolio standard was proposed. Of the bills included in
figure does not distinguish bills that exempted hydropower
this analysis, 14 (18%) had some action in addition to
or any other source from the compliance requirement. The
introduction and referral to committee. Seven of these were
third category of bills included non-hydro renewables,
passed in at least one chamber, but in all cases as part of a
hydropower, and additional nonrenewable sources like
more comprehensive energy or environmental bill. For
nuclear or CCS (yellow bars) as eligible sources. No
example, H.R. 2454 in the 111th Congress, the American
proposals included only nonrenewable sources.
Clean Energy and Security Act of 2009, passed the House.
Figure 1. Federal Portfolio Standard Proposals, by
Source Eligibility
Source Eligibility
A chief distinction among portfolio standard proposals is
which electricity generation sources may be used to fulfill
the requirement (i.e., source eligibility). A portfolio
standard might establish a requirement to procure electricity
from renewable sources such as wind, solar, biomass, or
geothermal energy. Many stakeholders refer to these as
renewable portfolio standards (RPS).
Alternatively, a portfolio standard might establish
requirements to procure electricity from a broader set of
sources like nuclear, efficient natural gas-fired, or fossil
fuel-fired power plants equipped with carbon capture and
sequestration (CCS) technology in addition to renewable
sources. Many stakeholders refer to this type of policy as a
clean energy standard (CES).

Source: CRS analysis,
Portfolio standard proposals differ in their treatment of
Notes: Bil s are categorized according to the set of eligible sources
hydropower, possibly reflecting the varying levels of
under the proposed portfolio standard. Differences in other design
support hydropower has among different stakeholders.
aspects, such as exemptions for certain sources from compliance
requirements, are not shown.

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A Brief History of U.S. Electricity Portfolio Standard Proposals
Of the 76 bills included in this analysis, 19 (25%) included
Other Developments
only non-hydro renewables or did not define “renewable
Market conditions and state policies might be relevant to
sources,” 47 (62%) included non-hydro renewables and
congressional consideration of portfolio standards.
hydropower, and 10 (13%) also included some
nonrenewable sources. Most proposals in the 105th-107th
The U.S. electricity generation profile has changed since
Congresses included non-hydro renewables only. In the
1997, as shown in Figure 3. The figure shows the share of
108th-115th Congresses, proposals that included non-hydro
generation from different sources. The total amount of
renewables and at least some hydro were the most common.
electricity generation was 3,492 terrawatt-hours (TWh) in
CES proposals that would include nonrenewable sources
1997 and 4,153 TWh in 2019. In both absolute terms and as
have been the least common overall, but were the majority
a share of the total, generation from coal has decreased
of proposals in the 116th Congress.
while generation from natural gas, wind, and solar has
increased. These trends are driven, in part, by changing
Target Stringency
capital costs for some technologies, changing fuel costs,
Another distinction among proposals is the stringency of
and changing consumer preferences, some of which may
the portfolio standard. Often, stringency is expressed as the
have been affected by federal tax incentives or other
final target, in terms of the percentage of covered electricity
policies. Many projections show these trends continuing.
sales to be procured from eligible sources. This topline
number often is interpreted as a measure of expected policy
Figure 3. U.S. Electricity Generation by Source
outcome, although it is an imperfect measure. The date by
which a final target must be achieved and other policy
design choices together determine the expected changes
from a business-as-usual scenario. Nonetheless, using final
targets as a proxy for policy outcome may be useful in
understanding changing congressional interest over time.
As Figure 2 shows, both the minimum proposed final target
and the maximum proposed final target in any Congress
have increased over time. In the 105th-108th Congresses, the
most stringent portfolio standard proposals by this measure
would have 20% of electricity procured from eligible
sources (target dates varied among proposals). In
comparison, no proposal from the 112th Congress onward
had a final target less than 25%. Beginning in the 112th
Congress, some proposals would target 80% or more of

electricity sales in the United States coming from eligible
Source: EIA, Electric Power Annual
sources. Of the eight proposals with this level of stringency,
Notes: Other includes EIA categories Petroleum, Other Gases, and
four include some nonrenewable sources. Additionally, one
Other. Generation shown as share of total because most portfolio
CES proposal in the 116th Congress did not specify final
standard proposals to date have expressed final targets in this way.
targets, but rather directed the Secretary of Energy to set
them to achieve 80% reductions in power sector carbon
The first state portfolio standard was established in Iowa in
dioxide emissions by 2050.
1983, and many states adopted similar policies in the 2000s.
Figure 2. Range of Final Targets in Federal Portfolio
Now, 30 states, the District of Columbia, and 3 U.S.
Standard Proposals
territories have mandatory portfolio standards. Eleven of
these jurisdictions have amended their portfolio standard to
have a final target of 100%, with most amendments
occurring since 2015: 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. These policies
vary in their policy details (e.g., eligible sources).
Additional Analysis
CRS Report R45913, Electricity Portfolio Standards:
Background, Design Elements, and Policy Considerations

CRS Report R46691, Clean Energy Standards: Selected
Source: CRS analysis,
Issues for the 117th Congress
Notes: Bottom and top of the bars indicate the minimum and
maximum proposed final target in any Congress, respectively. Al bil s
Ashley J. Lawson, Analyst in Energy Policy
in the 113th Congress had the same final target of 25%.

A Brief History of U.S. Electricity Portfolio Standard Proposals

This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
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