Without regard to the limitations specified in sections 837a and 837b of this title, the Secretary may enter into contracts for the exchange with areas other than the Pacific Northwest of (1) surplus energy during the Pacific Northwest storage refill period, (2) any hydroelectric energy during the Pacific Northwest storage refill period which will be returned to the Pacific Northwest in equal amounts during the same Pacific Northwest refill period or the succeeding storage drawdown period, (3) any hydroelectric energy which will be returned to the Pacific Northwest in equal amounts during the same Pacific Northwest storage drawdown period, (4) hydroelectric peaking capacity, or (5) surplus peaking capacity for energy. All benefits from such exchanges, including resulting increases of firm power, shall be shared equitably by the areas involved, having regard to the secondary energy and other contributions made by each.