1. Exclusion of energy efficiency proj­ects, pollution control projects, and reliability projects from the definition of a modification Section 111(a)(4) of the Clean Air Act ( 42 U.S.C. 7411(a)(4) ) is amended— (1) by striking (4) The term modification means and inserting the following: (4) Modification (A) In general The term modification means ; and (2) by adding at the end the following: (B) Exclusion The term modification does not include any energy efficiency project, pollution control project, or reliability project. (C) Associated definitions For purposes of subparagraph (B): (i) Energy efficiency project 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, the stationary 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 stationary source is lower than that rate was immediately before the project or activity, or the group of projects, activities, or changes, was undertaken