of national significance in accordance with paragraph (2). (2) Cost allocation principle The Commission shall require that any tariff described in paragraph (1) allocate the cost to construct, modify, and operate a transmission facility of national significance to customers within the applicable transmission planning region or regions in a manner that is roughly commensurate with the reasonably anticipated transmission benefits. (b) Definition of transmission facility of national significance In this section, the term transmission facility of national significance means— (1) an interstate electric power transmission line (and any facilities necessary for the operation of such electric power transmission line)— (A) that has a transmission capacity of not less than 1,000 megawatts