All receipts from the transmission and sale of electric power and energy under the provisions of section 825s of this title, generated or purchased in the southwestern power area, shall be covered into the Treasury of the United States as miscellaneous receipts, except that the Treasury shall set up and maintain from such receipts a continuing fund of $300,000, including the sum of $100,000 in the continuing fund established under the Administrator of the Southwestern Power Administration in the First Supplemental National Defense Appropriation Act, 1944 (57 Stat. 621), which shall be transferred to the fund established; and said fund of $300,000 shall be placed to the credit of the Secretary and shall be subject to check by him to defray emergency expenses necessary to insure continuity of electric service and continuous operation of the facilities, and to cover all costs in connection with the purchase of electric power and energy and rentals for the use of facilities for the transmission and distribution of electric power and energy to public bodies, cooperatives, and privately owned companies: Provided, That expenditures from this fund to cover such costs in connection with the purchase of electric power and energy and rentals for the use of facilities are to be made only in such amounts as may be approved annually in appropriation Acts.