Electricity generation technologies, including combined heat and power (CHP), have traditionally been subject to input-based emissions regulations, which define limits on the amount of emissions that can be produced per unit of fuel input (e.g., pounds of sulfur dioxide per million Btu of coal).

On the other hand, output-based emissions regulations define emissions limits based on the amount of pollution produced per unit of useful output (e.g., pounds of sulfur dioxide per megawatt-hour of electricity).  A major benefit of output-based emissions standards is that they encourage cost-effective, long-term pollution prevention through process efficiency.  Efficient distributed production of electricity from fossil fuels reduces fuel inputs compared to conventional generation and transmission systems, and leads to fewer emissions of all pollutants, not just those limited by regulation.  Output-based emissions standards thus recognize both the efficiency and pollution prevention benefits of CHP and other distributed generation systems, which is not the case with input-based standards.

ACEEE tracks air emissions regulations at the state level in our state policy database and we assess them in our annual State Energy Efficiency Scorecard.

⇒ FInd out which states have output-based air emissions regulations in place with ACEEE's State Energy Efficiency Policy Database.

⇒ Learn about best practices for state air emissions regulations with ACEEE's State Technical Assistance Toolkit.