The following papers by U.S. experts describe a new approach to power plant air emission regulation: output-based Generation Performance Standards (GPS). The concept of 'generation performance standards,' or equivalently 'emission performance standards,' has evolved in the U.S. in recent years as state and federal regulators, addressing the consequences of electric industry restructuring, have sought mechanisms for assuring environmental protection in newly competitive electricity markets. Output-based standards are well suited to a competitive electric industry and they provide a mechanism for promoting greater efficiency in the generation of electric power regardless of plant age or historic fuel use.
Output-Based Emission Control Programs: U.S. Experience (May 2000)

Setting and Administering Output-Based Emission Standards for the Power Sector: A Case Study of the Massachusetts Output-Based Emission Control Programs (October 2001)