Wind Powering America Fact Sheet Series

The Montgomery 

County, Maryland 

buying group purchases 

wind energy from the 

Mountaineer Wind 

Energy Center in West 

Virginia.

This fact sheet provides an overview of how electricity generated from 

zero-emission wind energy can help states and municipalities improve 

air quality, achieve attainment of Clean Air Act standards, and reduce 

pollution control costs for taxpayers. 

States and municipalities are required to comply with the standard 

for ground-level ozone established under the Clean Air Act.1 Wind 

energy can help states and municipalities improve air quality. 

Electricity generated from zero-emission wind power can displace 

electricity generated from coal, oil, and natural gas plants, which 

reduces conventional air pollutants, such as nitrogen oxides (NOx), 

and greenhouse gas emissions (such as carbon dioxide). 

Wind energy is often less expensive than other control measures in 

achieving emission reductions. As a result, wind energy can help a 

state or municipality that does not meet the air quality standard 

reduce the pollution control costs paid by taxpayers. 

Wind Energy in State Implementation Plans (SIPs)

Under guidance issued by the U.S. Environmental Protection Agency 

(EPA) in August 2004, states and municipalities can receive emission 

reduction credit in their State Implementation Plans (SIPs) for wind 

power purchases that reduce air emissions and help achieve 

attainment of the National Ambient Air Quality Standard for ozone.2

The National Renewable Energy Laboratory (NREL) provides model 

SIP documentation to assist states in achieving this objective.3 In 

states with NOx emissions “cap and trade” programs, the EPA guidance 

generally requires the state to retire NOx allowances when the 

renewable generation comes online. As a result, the EPA guidance is 

particularly relevant to states that have adopted renewable energy setasides as part of their NOx emissions trading programs. These states 

include Indiana, Maryland, Massachusetts, New Jersey, New York, and 

Ohio.4 The renewable set-asides allow NOx allowances to be assigned 

to wind developers, states, or municipalities, thus providing a pool of 

NOx allowances that can be retired to achieve SIP credit. 

The EPA guidance and NREL documentation are also relevant to states 

that have not adopted renewable energy set-asides but are interested 

in promoting clean air with wind energy purchases. These states 

should implement mechanisms, such as new enforcement approaches 

or modifications to their NOx emissions trading regulations, to achieve 

SIP credit. Regulatory changes may be needed because most of the 

current state emission trading regulations only allow the assignment 

of NOx allowances to fossil fuel generating sources. As a result, these 

states often do not have a pool of allowances to assign to renewable 

energy generators.

Improving Regional Air 

Quality with Wind Energy

Improving Regional Air Quality with Wind Energy

Alden Hathaway/PIX13965

Improving Regional Air 

Quality with Wind Energy
Top photo page 1: Geothermal Education Office, Tiburon, California

A Strong Energy Portfolio for a Strong America

Energy efficiency and clean, renewable energy will mean a stronger economy, a cleaner 

environment, and greater energy independence for America. Working with a wide array of state, 

community, industry, and university partners, the U.S. Department of Energy’s Office of Energy 

Efficiency and Renewable Energy invests in a diverse portfolio of energy technologies. 

For more information contact:

EERE Information Center

1-877-EERE-INF (1-877-337-3463)

www.eere.energy.gov

Produced for the U.S. Department of Energy by the 

National Renewable Energy Laboratory, 

a DOE national laboratory

Printed with a renewable-source ink on paper containing at 

least 50% wastepaper, including 20% postconsumer waste

DOE/GO-102005-2134 • May 2005

States seeking to gain NOx emission reduction credit for wind energy 

purchases in their SIPs must demonstrate that the emission reductions are: 

• Quantifiable. The emission reductions must be subject to 

measurement.

• Surplus. The emission reductions cannot be included in both the 

baseline emissions inventory and a SIP control measure. The 

reductions must also be deemed in excess of requirements imposed 

by the state’s NOx emissions trading program.

• Enforceable. Properly structured wind energy purchases should 

be treated as enforceable under EPA’s voluntary measures policy.

• Permanent. The wind purchase should be permanent throughout 

the term of the SIP, unless necessary emission reductions can be 

secured from other actions later in the term.5

The state can ensure that air quality improvements are achieved by 

requiring the retirement of NOx allowances from future use from its 

renewable energy set-aside in an amount commensurate with the size 

of the wind energy purchase. This can be accomplished by: (1) the 

direct retirement of the NOx allowances by the state, or (2) the award 

of the allowances to a municipality or wind developer on the condition 

that the allowances be retired from future use.

Case Study: Montgomery County, Maryland 

Wind Energy Purchase 

The metropolitan Washington area was designated a “severe” ozone 

non-attainment area under the 1-hour standard. In February 2004, 

Maryland, Virginia, and the District of Columbia approved SIPs to 

improve air quality in the Washington metropolitan area to meet the 

National Ambient Air Quality Standard for ground-level ozone. These 

SIPs include the first state EPA submissions of wind energy purchases 

as control measures in regional air quality plans required under the 

Clean Air Act. The EPA issued a Federal Register notice in December 

2004 proposing the approval of these measures.6 The wind purchase 

measures are designed to reduce dangerous ozone transport caused 

by fossil fuel generation in upwind areas.

The wind purchases were spearheaded by Montgomery County and the 

State of Maryland through their joint membership in the Metropolitan 

Washington Council of Governments (MWCOG) Air Quality Committee. 

Montgomery County and its partners committed to purchase 5% of 

their total energy consumption through wind energy, which equals 

38,400 megawatt-hours (MWh) per year. This represents the largest 

wind purchase by a local government group. In its regional wind 

purchase initiative, Montgomery County successfully built a consortium 

of green power users by recruiting purchases from neighboring Prince 

George’s County, numerous cities and towns within the county, local 

schools and colleges, the local water and wastewater agency, several 

local housing authorities, and the local park authority to enhance the 

county’s ability to secure a cost-competitive bid. 

Based on information provided by electric utilities, the wind energy 

purchase by the Montgomery County buying group impacts electric 

generation from coal-fired units in the PJM West electric grid. This 

wind purchase results in the reduction of air emissions of NOx (as well 

as other pollutants and greenhouse gases) from these coal-fired units.

Displacement occurs among a set of plants that are on a variable 

dispatch schedule so that the actual generation rises and falls with 

the demand. 

The total emissions reduction credited in the SIP for the wind purchase 

is 2.9 pounds of NOx per MWh of wind electricity generated – 

equivalent to 9.2 tons during the summer ozone season.7 The Maryland 

Department of Environment plans to retire NOx allowances from its 

renewable energy set-aside commensurate with this reduction. 

According to Montgomery County, the cost of the wind purchase 

compared favorably with other control measures considered by the 

MWCOG, including compressed natural gas (CNG) refueling stations, 

CNG bus purchases, and bike lockers.

_____________

1 Ground-level ozone is formed when volatile organic compounds combine with 

nitrogen oxides in the presence of sunlight on hot, stagnant, summer days

2 EPA guidance can be found at www.epa.gov/ttn/oarpg/t1/memoranda/

ereseerem_gd.pdf 

3 Model documentation can be found at www.windpoweringamerica.gov/sips

4 See www.eandeclearinghouse.com for the state regulations implementing 

the NOx renewable energy set-aside in each of these states

5 Refer to EPA guidance at www.epa.gov/ttn/oarpg/t1/memoranda/ereseerem_

gd.pdf for a more complete description of these requirements

6 69 Fed. Reg. 76889, December 23, 2004

7 This estimate is conservative for several reasons, including the fact that the 

participants in the buying group and the MWh ultimately purchased increased 

substantially following the SIP submission 

For more information about wind energy in state implementation plans, 

please contact:

Debra Jacobson

DJ Consulting LLC

(703) 356-7448

djconsultingllc@earthlink.net

Alden Hathaway

Environmental Resources Trust, Inc.

(202) 785-8577

ahathaway@ert.net 

Colin High

Resource Systems Group

(802) 295-4999

chigh@rsginc.com