The Postmaster General of the United States Postal Service , the Administrator of the General Services Administration , the Secretary of Defense , and the heads of other Federal agencies shall— (1) carry out a study of the practicability of using electric and hybrid vehicles in the performance of some or all of the functions of their agencies; and (2) arrange for the introduction of electric and hybrid vehicles into their fleets as soon as possible. For competitive procurement purposes in purchasing such vehicles, life-cycle costing and any beneficial air pollution control characteristics of electric and hybrid vehicles shall be fully taken into account. If the head of the agency involved determines that electric or hybrid vehicles are technologically practicable, but that they are not completely economically competitive with conventional vehicles, the Secretary of Energy may, for purposes of the demonstration program described in section 2506 of this title , pay to such agency the incremental costs of the electric or hybrid vehicles, including differential operating costs. ( Pub. L. 94–413, § 11 , Sept. 17, 1976 , 90 Stat. 1268 ; Pub. L. 95–91, title III, § 301(a) , Aug. 4, 1977 , 91 Stat. 577 .) Statutory Notes and Related Subsidiaries Transfer of Functions “Secretary of Energy” substituted in text for “Administrator” pursuant to section 301(a) of Pub. L. 95–91 , see Codification note set out under section 2502 of this title .