; (C) codes and standards savings of natural gas; and (D) fuel switching energy savings that results in net savings of natural gas. (13) Power pool The term power pool means an association of two or more interconnected electric systems that have entered into an agreement to coordinate operations and planning for improved reliability and efficiencies, including a Regional Transmission Organization or an Independent System Operator, as determined by the Secretary. (14) Reporting period The term reporting period means— (A) calendar year 2019; and (B) each successive 2-calendar-year period thereafter. (15) Retail electricity supplier (A) In general The term retail electricity supplier means, for any given calendar year, an electric utility that sells not less than 1,000,000 megawatt hours of electric energy to electric consumers for purposes other than resale during the preceding calendar year. (B) Inclusions and limitations For purposes of determining whether an electric utility qualifies as a retail electricity supplier under subparagraph (A)— (i) deliveries by any affiliate of an electric utility to electric consumers for purposes other than resale shall be considered to be deliveries by the electric utility