(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 (as defined in section 54A(e)(4)) 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 one or more qualified facilities, (B) the bond is issued by— (i) a governmental body (as defined in paragraph (3) of section 54C(d)), (ii) a public power provider (as defined in paragraph (2) of such section), or (iii) a cooperative electric company (as defined in paragraph (4) of such section), 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 (a) or section 6433, (B) for purposes of section 148, the yield on a clean energy bond shall be determined without regard to the credit allowed under subsection (a), and (C) a bond shall not be treated as a clean energy bond if the issue price has more than a de minimis amount (determined under rules similar to the rules of section 1273(a)(3)) of premium over the stated principal amount of the bond. (3) Qualified facility The term qualified facility means