The program established by section 8272 of this title shall provide for the acquisition of photovoltaic solar electric systems and associated storage capability by the Secretary for their use by Federal agencies, and for the acquisition of such systems and associated capability by Federal agencies for their own use in cases where the authority to make such acquisition has been delegated to the agency involved by the Secretary. The acquisition of photovoltaic solar electric systems shall be at an annual level substantial enough to allow use of low-cost production techniques by suppliers of such systems. The Secretary (or other Federal agency acting under delegation from the Secretary) is authorized to make such acquisitions through the use of multiyear contracts. Authority under this part to enter into acquisition contracts shall be only to the extent as may be provided in advance in appropriation Acts.