(a) As used in this Section:(1) "CWIP" means those assets which are recorded as construction work in progress on a public utility's books of accounts maintained in accordance with the applicable regulations and orders of the Commission.(2) "Rate base" means the original cost value of the property on which a return is allowed.(3) "CWIP ratio" means the fraction, expressed as a percentage, calculated by dividing the amount of CWIP included in a public utility's rate base by the utility's rate base.(4) "Existing CWIP" means the amount of CWIP included in the rate base on December 1, 1983.(b) In any determination under Section 9-201, 9-202 or 9-250 of this Act in a proceeding begun on or after December 1, 1983: (1) For any public utility with a CWIP ratio on December 1, 1983, which is less than 15%, the Commission shall not include in the rate base for such public utility an amount for CWIP to exceed 80% of existing CWIP for the period from December 1, 1983 through December 31, 1984, and 60% of existing CWIP for the period from January 1, 1985 through December 31, 1985 and 40% of existing CWIP for the period from January 1, 1986 through December 31, 1986, and 20% of existing CWIP for the period from January 1, 1987 through December 31, 1987.(2) For any public utility with a CWIP ratio on December 1, 1983 which is greater than or equal to 15%, the Commission shall not include in the rate base for such public utility an amount for CWIP in excess of the amount of CWIP included in the rate base on December 1, 1983, plus 50% of the allowed construction expenses incurred by the public utility from the date of the most recent rate determination by the Commission prior to December 1, 1983.(c) The limitations set forth in paragraph (b) of this Section shall not be interpreted as an expansion of the Commission's authority to include CWIP in the rate base, but rather solely as a limitation thereon.(d) The Commission shall not include an amount for CWIP in the rate base for any public utility for the period after December 31, 1988.(e) Notwithstanding the provisions of paragraphs (b) and (d) of this Section the Commission may include in the rate base of a public utility an amount for CWIP for a public utility's investment which is scheduled to be placed in service within 12 months of the date of the rate determination. For the purposes of this paragraph nuclear generating facilities shall be considered to be in service upon the commencement of electric generation.(f) Notwithstanding the provisions of paragraph (b) and (d), the Commission may include in the rate base of a public utility an amount of CWIP for a public utility's investment in pollution control devices for the control of sulfur dioxide emissions and the purification of water and sewage; provided, however, that upon application by a public utility which is constructing one or more pollution control devices for the control of sulfur dioxide emissions as part of a Clean Air Act compliance plan approved by the Commission pursuant to subsection (e) of Section 8-402.1, the Commission shall include in such public utility's rate base an amount of CWIP equal to its investment in such pollution control device or devices, but not to exceed the estimated cost of such facilities specified in the Commission's order or supplemental order pursuant to subsection (e) of Section 8-402.1. For purposes of this subsection (f), the public utility's investment shall not include the amount of any state, federal or other grants provided to the public utility to fund the design, acquisition, construction, installation and testing of pollution control devices for the control of sulfur dioxide emissions.(g) Except for those amounts of CWIP described in paragraphs (e) and (f) of this Section, the Commission shall consider, in any rate filing subsequent to the coming on line of any new utility plant where CWIP funds have been allowed in rate base, a rate moderation plan directed towards allowing an appropriate return to ratepayers for previous amounts attributable to CWIP funds. Amended by P.A. 100-0840,§ 10, eff. 8/13/2018.