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Updated October 20, 2020
A Brief History of U.S. Electricity Portfolio Standard Proposals
Electricity portfolio standards are designed to change the
Portfolio standard proposals differ in their treatment of
set of energy sources used to generate electricity, usually by
hydropower, possibly reflecting the different levels of
establishing requirements on utilities to procure a
support hydropower has among different stakeholders.
percentage of electricity from specified eligible sources.
Some proposals include hydropower in their definition of
Since the 105th Congress, over 70 proposals for a national
renewable sources, albeit often with restrictions based on
portfolio standard have been introduced, but none has
size or age, while other proposals exclude hydropower in
become law. This analysis provides historical context on
favor of non-hydro renewables. Many of the proposals
federal portfolio standard proposals.
identified by CRS (41) took an intermediate approach,
exempting hydropower from the compliance requirement.
Previous Federal Proposals
Sources that are exempted from a portfolio standard
CRS searched to assemble a comprehensive
requirement could receive indirect financial incentives. The
list of all federal portfolio standard proposals. A full
level of support for exempted sources would likely be less
description of the search methodology and the list of
than the support for eligible sources, but more than the
previous legislation is available in CRS Report R45913,
support for ineligible sources. Some proposals also
Electricity Portfolio Standards: Background, Design
exempted other sources in addition to hydropower such as
Elements, and Policy Considerations.
municipal solid waste (23 proposals) and new nuclear
power plants (5 proposals).
CRS identified 74 proposals, with the earliest identified bill
introduced in 1997 in the 105th Congress. Some proposals
Figure 1 categorizes bills according to the types of sources
were stand-alone; in other words, a national portfolio
that would be eligible. All bills included some non-hydro
standard was the only provision in the bill. Other proposals
renewables, though there were differences about eligibility
included a portfolio standard alongside other provisions.
for some types of sources, especially biomass. The
introduced bills that only included non-hydro renewables
As Figure 1 shows, the number of introduced bills was
are represented by blue bars in the figure. The majority of
highest in the 110th Congress. The 115th Congress saw the
bills included some hydropower for eligibility in addition to
fewest number of introduced bills of any Congress in which
non-hydro renewables, though some of these had age or
a portfolio standard was proposed. Of the bills included in
size restrictions (orange bars). The figure does not
this analysis, 14 (19%) had some action other than
distinguish bills that exempted hydropower or any other
introduction and referral to committee. Seven of these were
source from the compliance requirement. The third category
voted favorably in at least one chamber, but in all cases as
of bills in this analysis included non-hydro renewables,
part of a more comprehensive energy or environmental bill.
hydropower, and additional nonrenewable sources like
For example, H.R. 4 in the 107th Congress, the Energy
nuclear or CCS (gray bars) as eligible sources. No
Policy Act of 2002, passed both chambers, though it did not
proposals included only nonrenewable sources.
become law. H.R. 2454 in the 111th Congress, the American
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).
A portfolio standard might alternatively 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

Source: CRS analysis,
clean energy standard (CES).
Notes: Bil s are categorized according to the set of eligible sources
under the proposed portfolio standard. Differences in other design
aspects, such as exemptions for certain sources from compliance

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A Brief History of U.S. Electricity Portfolio Standard Proposals
requirements, are not shown. Information for the 116th Congress is
Other Developments
as of October 14, 2020.
Congressional interest in portfolio standard policies can be
influenced by many factors, including market conditions
Of the 74 bills included in this analysis, 19 (26%) included
and state policy developments. Some of the developments
only non-hydro renewables, 46 (62%) included non-hydro
that may have influenced past proposals are discussed here.
renewables and hydropower, and 9 (12%) also included
No attempt has been made to attribute any specific external
some nonrenewable sources. Most proposals in the 105th-
factor or motivation to any particular proposal.
107th Congresses included non-hydro renewables only.
Beginning with the 108th Congress, proposals that include
The U.S. electricity generation profile has changed since
non-hydro renewables and hydropower have been the most
1997, as shown in Figure 3. The figure shows the share of
common. CES proposals that would include nonrenewable
generation from different sources. The total amount of
sources have been the least common overall. They were
electricity generation was 3,492 terrawatt-hours (TWh) in
also the latest type to be introduced, with the first proposal
1997 and 4,153 TWh in 2019. In both absolute terms and as
in the 110th Congress.
a share of the total, generation from coal has decreased
while generation from natural gas, wind, and solar has
Target Stringency
increased. These trends are driven, in part, by changing
Another distinction among proposals is the stringency of
capital costs for some technologies, changing fuel costs,
the portfolio standard. Stringency is often expressed as the
and changing consumer preferences, some of which may
final target, in terms of the percentage of electricity sales to
have been affected by federal tax incentives or other
be procured from eligible sources. This topline number is
policies. Many projections show these trends continuing.
often interpreted as a measure of expected policy outcome,
although it is an imperfect measure. The date by which a
Figure 3. U.S. Electricity Generation by Source
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 has
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

sources. Of the seven proposals with this level of
Source: EIA, Electric Power Annual,
stringency, four include some nonrenewable sources.
Notes: Other includes EIA categories Petroleum, Other Gases, and
Figure 2. Range of Final Targets in Federal Portfolio
Other. Generation shown as share of total because most portfolio
Standard Proposals
standard proposals to date have expressed final targets in this way.
The first state portfolio standard was established in Iowa in
1983, and many states adopted similar policies in the 2000s.
Now, 30 states, the District of Columbia, and 3 U.S.
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 details including final target year and eligible
Source: CRS analysis,
Notes: Bottom and top of the bars indicate the minimum and
maximum proposed final target in any Congress, respectively. Al bil s
Additional Analysis
in the 113th Congress had the same final target of 25%.
CRS Report R45913, Electricity Portfolio Standards:
Background, Design Elements, and Policy Considerations
by Ashley J. Lawson

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

Ashley J. Lawson, Analyst in Energy Policy

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