of construction Section 48(c) is amended by adding at the end the following new paragraph: (5) Special rule for determining beginning of construction The construction of any facility, modification, improvement, addition, or other property shall not be treated as beginning before any date unless there is a continuous program of construction which begins before such date and ends on the date that such property is placed in service. . (l) Effective date (1) In general Except as otherwise provided in this subsection, the amendments made by this section shall apply to periods after December 31, 2016, under rules similar to the rules of section 48(m) of the Internal Revenue Code of 1986 (as in effect on the day before the date of the enactment of the Revenue Reconciliation Act of 1990). (2) Extension of combined heat and power system property The amendment made by subsection (d) shall apply to property placed in service after December 31, 2016. (3) Phaseouts and terminations The amendments made by subsections (g), (h), (i), and (j) shall take effect on the date of the enactment of this Act. (4) Special rule for determination of beginning of construction The amendment made by subsection (k) shall apply to taxable years beginning before, on, or after the date of the enactment of this Act. 3503. Extension and phaseout of residential energy efficient property (a) Extension Section 25D(h) is amended by striking December 31, 2016 (December 31, 2021, in the case of any qualified solar electric property expenditures and qualified solar water heating property expenditures) and inserting December 31, 2021 . (b) Phaseout (1) In general Paragraphs (3), (4), and (5) of section 25D(a) are amended by striking 30 percent each place it appears and inserting the applicable percentage . (2) Conforming amendment Section 25D(g) of such Code is amended by striking paragraphs (1) and (2) of . (c) Effective date The amendments made by this section shall apply to property placed in service after December 31, 2016. 3504. Repeal of enhanced oil