1. Exclusion of energy efficiency projects, pollution control projects, and reliability projects from the definition of a modification Section 111(a) of the Clean Air Act ( 42 U.S.C. 7411(a) ) is amended— (1) in paragraph (4)— (A) by striking The term modification means and inserting the following: The term modification — (A) means ; (B) by striking the period at the end of the paragraph and inserting ; and ; and (C) by adding at the end the following: (B) excludes any energy efficiency project, pollution control project, or reliability project. ; and (2) by adding at the end the following: (9) For purposes of paragraph (4)(B): (A) The term energy efficiency project means any project or activity undertaken at a stationary source (including any physical change in, or change in the method of operation of, such source) or any group of projects, activities, or changes undertaken during the same outage period— (i) as a result of which the maximum hourly carbon dioxide emissions rate of the source is lower than it was immediately before such project or activity, or such group of projects, activities, or changes, was undertaken