under subparagraph (A) is not a whole percentage point, such percentage shall be rounded to the nearest whole percentage point. (C) Safe harbor rules Rules similar to the rules of sections 45T(b)(3) and 45U(b) shall apply for purposes of this section. (c) Limitation based on amount of tax (1) In general The credit allowed under subsection (a) for any taxable year shall not exceed the excess of— (A) the sum of the regular tax liability (as defined in section 26(b)) plus the tax imposed by section 55, over (B) the sum of the credits allowable under this part (other than subpart C and this subpart). (2) Carryover of unused credit If the credit allowable under subsection (a) exceeds the limitation imposed by paragraph (1) 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 taxable year (determined before the application of paragraph (1) for such succeeding taxable year). (d) Clean energy bond (1) In general For purposes of this section, the term clean energy bond means any bond issued as part of an issue if— (A) 100 percent of the excess of the available project proceeds of such issue over the amounts in a reasonably required reserve (within the meaning of section 150(a)(3)) with respect to such issue are to be used for capital expenditures incurred by an entity described in subparagraph (B) for— (i) 1 or more qualified facilities, (ii) qualified carbon capture and sequestration equipment (as defined in subsection (c)(2) of section 48D), or (iii) energy storage property (as defined in subsection (d)(2) of such section), (B) the bond is issued by— (i) a governmental body, (ii) a public power provider, or (iii) a cooperative electric company, and (C) the issuer makes an irrevocable election to have this section apply. (2) Applicable rules For purposes of applying paragraph (1)— (A) for purposes of section 149(b), a clean energy bond shall not be treated as federally guaranteed by reason of the credit allowed under subsection