property (A) In general The Secretary, in consultation with the Administrator of the Environmental Protection Agency, shall establish safe-harbor greenhouse gas emissions rates for types or categories of qualified property which are for use in a dwelling unit, which a taxpayer may elect to use for purposes of this section. (B) Rounding In establishing the safe-harbor greenhouse gas emissions rates for qualified property, the Secretary may round such rates to the nearest multiple of 32.5 grams of CO 2 e per KWh (or, in the case of a greenhouse gas emissions rate which is less than 16.25 grams of CO 2 e per KWh, by rounding such rate to zero). (b) Qualified property The term qualified property means property— (1) which is tangible personal property, (2) which is used for the generation of electricity, (3) which is constructed, reconstructed, erected, or acquired by the taxpayer, (4) the original use of which commences with the taxpayer, and (5) which is originally placed in service after December 31, 2018. (c) Energy storage property The term energy storage property means property which— (1) receives, stores, and delivers electricity or energy for conversion to electricity which is consumed by the taxpayer, and (2) is equipped with a metering device which is owned and operated by an unrelated person. (d) Carryforward of unused credit If the credit allowable under subsection (a) exceeds the limitation imposed by section 26(a) for such taxable year reduced by the sum of the credits allowable under this subpart (other than this section), such excess shall be carried to the succeeding taxable year and added to the credit allowable under subsection (a) for such succeeding taxable year. (e) Credit phase-Out (1) In general If the Secretary determines that the annual greenhouse gas emissions from electrical production in the United States are equal to or less than the percentage specified in section 48E(g), the amount of the credit allowable under subsection (a) for any qualified property or energy storage property placed