Power plant greenhouse gas standards

We set emissions standards for power plants in Washington. Power plants covered by Chapter 173-407 WAC are required to meet greenhouse gas emission performance standards and carbon dioxide sequestration conditions.

About this regulation

Ecology and local clean air agencies regulate small plants that generate more than 25 megawatts of electricity (MWe), but less than 350 MWe. Plants are required to meet greenhouse gas emission standards and offset, or mitigate, their carbon pollution under this rule.

The Energy Facility Site Evaluation Council (EFSEC) regulates plants larger than 350 MWe.

All power plants in Washington, or a power plant with an agreement with a retail utility serving customers in Washington, must meet a greenhouse gas emission performance standard. Renewable and nuclear-powered electricity, and long-term contracts with the Bonneville Power Administration, are exempt from the rule's requirements.

TransAlta, a power plant in Centralia, has special requirements set by the Legislature. The TransAlta plant must comply with the greenhouse gas emission performance standard for one boiler by 2020 and the other boiler by 2025.

Greenhouse gas emissions performance standards

Chapter 173-407 WAC establishes greenhouse gas emissions performance standards. The standard applies to electric generating plants or electric cogenerating plants that are designed and permitted to operate at 60 percent or greater capacity (known as their baseload generation).

The Washington Department of Commerce must review the emissions performance standard every five years.

Applicable dates

Greenhouse gas emissions performance standard
(pounds per megawatt-hour)

July 1, 2009 – March 23, 2018 1100
March 24, 2018 – Sept. 19, 2018  970
Sept. 20, 2018 – forward  925

When does the standard apply?

  • A new power plant starts operating.
  • An existing power plant changes ownership.
  • An existing power plant installs a new unit.
  • An existing power plant or unit gets modified and increases fuel usage.
  • An investor-owned or consumer-owned utility signs a long-term contract (5 or more years) with a baseload generating or cogenerating plant. 

Sequestration plans

A power plant using non-geologic sequestration of greenhouse gases must submit a sequestration plan to Ecology or EFSEC for approval to meet the emissions performance standards.

Permanently-sequestered greenhouse gas emissions do not count toward compliance.

Carbon dioxide mitigation

New or modified thermal power plants larger than 25 megawatts must mitigate or offset their carbon dioxide emissions. 

A fossil-fueled thermal electric generation unit must mitigate or offset the equivalent of 20 percent of the potential carbon dioxide (CO2) emissions that could be emitted over 30 years. Examples of these types of units are:

  • Boilers that run on coal, oil, natural gas, or coke.
  • Combustion turbines.
  • Coal gasification units that produce synthesis gas or hydrogen for a fuel cell.
  • Hydrocarbon reformer emissions where the hydrogen produced is used in fuel cells.

Mitigation plans may include any combination of:

  • Payment to a third party to provide mitigation.
  • Direct purchase of a permanent carbon credit.
  • Direct investment in an applicant-controlled carbon dioxide (CO2) mitigation project including cogeneration.

When does a mitigation plan apply?

  • A new power plant starts operating.
  • An existing plant increases its carbon dioxide emissions by 15 percent or more.
  • An existing plant modifies its operations to increase its capacity by at least 25,000 kilowatts.