92 STAT. 3176
PUBLIC LAW 95-618—NOV. 9, 1978 " (6) CARRYOVER OF UNUSED CREDIT.—
" (A) IN GENERAL.—If the credit allowable under subsection (a) for any taxable year exceeds the limitation imposed by paragraph (5) for such taxable year, such excess shall be carried to the succeeding taxable year and added to the credit allowable under subsection (a) for such succeeding taxable year.
N o CARRYOVER TO TAXABLE YEARS BEGINNING AFTER
DECEMBER 31, 198 7.—No amount may be carried under subparagraph (A) to any taxable year beginning after December 31, 1987.
" (c) DEFINITIONS AND SPECIAL
section— " (1) E N E R G Y CONSERVATION EXPENDITURES.—The term 'energy
conservation expenditure' means an expenditure made on or after April 20, 1977, by the taxpayer for insulation or any other energyconserving component (or for the original installation of such insulation or other component) installed in or on a dwelling unit— " (A) which is located in the United States, " (B) which is used by the taxpayer as his principal residence, and " (C) the construction of which was substantially completed before April 20, 1977. " (2) RENEWABLE ENERGY SOURCE EXPENDITURE.—
" (A) IN GENERAL.—The term 'renewable energy source expenditure' means an expenditure made on or after April 20, 1977, by the taxpayer for renewable energy source property installed in connection with a dwelling unit— " (i) which is located in the United States, and " ( i i) which is used by the taxpayer as his principal residence. "(B)
CERTAIN LABOR COSTS INCLUDED.—The term 'renew-
able energy source expenditure' includes expenditures for labor costs properly allocable to the onsite preparation, assembly, or original installation of renewable energy source property. " (C) S W I M M I N G POOL, ETC., USED AS STORAGE MEDIUM.—The
term 'renewable energy source expenditure' does not include any expenditure properly allocable to a swimming pool used as an energy storage medium or to any other energy storage medium which has a p r i m a r y function other than the function of such storage. " (3) INSULATION.—The term 'insulation' means any item— " (A) which is specifically and primarily designed to reduce when installed in or on a dwelling (or water heater) the heat loss or gain of such dwelling (or water h e a t e r), " (B) the original use of which begins with the taxpayer, " (C) which can reasonably be expected to remain in operation for a t least 3 years, and " (D) which meets the performance and quality standards (if any) which— " (i) have been prescribed by the Secretary by regulations, and " ( i i) are in effect a t the time of the acquisition of the item.