means a fan used in a natural gas, propane, or oil furnace and which has an annual electricity use of no more than 2 percent of the total annual energy use of the furnace (as determined in the standard Department of Energy test procedures). (e) Special rules For purposes of this section— (1) Application of rules Rules similar to the rules under paragraphs (4), (5), (6), (7), and (8) of section 25D(e) shall apply. (2) Joint ownership of energy items (A) In general Any expenditure otherwise qualifying as an expenditure under this section shall not be treated as failing to so qualify merely because such expenditure was made with respect to two or more dwelling units. (B) Limits applied separately In the case of any expenditure described in subparagraph (A), the amount of the credit allowable under subsection (a) shall (subject to paragraph (1)) be computed separately with respect to the amount of the expenditure made for each dwelling unit. (3) Property financed by subsidized energy financing For purposes of determining the amount of expenditures made by any individual with respect to any property, there shall not be taken into account expenditures which are made from subsidized energy financing (as defined in section 48(a)(4)(C)). (f) Basis adjustments For purposes of this subtitle, if a credit is allowed under this section for any expenditure with respect to any property, the increase in the basis of such property which would (but for this subsection) result from such expenditure shall be reduced by the amount of the credit so allowed. (g) Termination This section shall not apply with respect to any property placed in service— (1) after December 31, 2007, and before January 1, 2009, or (2) after December 31, 2021. . (b) Conforming amendments (1) Section 1016(a)(33) is amended by striking section 25C(g) and inserting 25C(f) . (2) Section 6213(g)(2) is amended— (A) by adding and at the end of subparagraph (P), (B) by striking the comma at the end of subparagraph (Q) and inserting a period, and (C) by striking