As used in this part—

(1) The term "appliance" means any article, such as a room air-conditioner, refrigerator-freezer, or dishwasher, which the Secretary classifies as an appliance for purposes of this part.

(2) The term "building" means any structure which includes provision for a heating or cooling system, or both, or for a hot water system.

(3) The term "energy audit" means any process which identifies and specifies the energy and cost savings which are likely to be realized through the purchase and installation of particular energy conservation measures or renewable-resource energy measures and which—

(A) is carried out in accordance with rules of the Secretary; and

(B) imposes—

(i) no direct costs, with respect to individuals who are occupants of dwelling units in any State having a supplemental State energy conservation plan approved under section 6327 ¹ of this title, and

(ii) only reasonable costs, as determined by the Secretary, with respect to any person not described in clause (i).

Rules referred to in subparagraph (A) may include minimum qualifications for, and provisions with respect to conflicts of interest of, persons carrying out such energy audits.

(4) The term "energy conservation measure" means a measure which modifies any building, building system, energy consuming device associated with the building, or industrial plant, the construction of which has been completed prior to May 1, 1989, if such measure has been determined by means of an energy audit or by the Secretary, by rule under section 6325(e)(1) of this title, to be likely to maintain or improve the efficiency of energy use and to reduce energy costs (as calculated on the basis of energy costs reasonably projected over time, as determined by the Secretary) in an amount sufficient to enable a person to recover the total cost of purchasing and installing such measure (without regard to any tax benefit or Federal financial assistance applicable thereto) within the period of—

(A) the useful life of the modification involved, as determined by the Secretary, or

(B) 15 years after the purchase and installation of such measure,

whichever is less. Such term does not include (i) the purchase or installation of any appliance, (ii) any conversion from one fuel or source of energy to another which is of a type which the Secretary, by rule, determines is ineligible on the basis that such type of conversion is inconsistent with national policy with respect to energy conservation or reduction of imports of fuels, or (iii) any measure, or type of measure, which the Secretary determines does not have as its primary purpose an improvement in efficiency of energy use.

(5) The term "industrial plant" means any fixed equipment or facility which is used in connection with, or as part of, any process or system for industrial production or output.

(6) The term "renewable-resource energy measure" means a measure which modifies any building or industrial plant, the construction of which has been completed prior to August 14, 1976, if such measure has been determined by means of an energy audit or by the Secretary, by rule under section 6325(e)(1) of this title, to—

(A) involve changing, in whole or in part, the fuel or source of the energy used to meet the requirements of such building or plant from a depletable source of energy to a nondepletable source of energy; and

(B) be likely to reduce energy costs (as calculated on the basis of energy costs reasonably projected over time, as determined by the Secretary) in an amount sufficient to enable a person to recover the total cost of purchasing and installing such measure (without regard to any tax benefit or Federal financial assistance applicable thereto) within the period of—

(i) the useful life of the modification involved, as determined by the Secretary, or

(ii) 25 years after the purchase and installation of such measure,

whichever is less.

Such term does not include the purchase or installation of any appliance.

(7) The term "public building" means any building which is open to the public during normal business hours.

(8) The term "transportation controls" means any plan, procedure, method, or arrangement, or any system of incentives, disincentives, restrictions, and requirements, which is designed to reduce the amount of energy consumed in transportation, except that the term does not include rationing of gasoline or diesel fuel.