Sec. 1. As used in this chapter, "applicable percentage" means the percentage determined as follows:
(1) If a plant was placed in service at least fifteen (15) years ago but less than thirty (30) years ago, the applicable percentage is fifteen percent (15%).
(2) If a plant was placed in service at least thirty (30) years ago but less than forty (40) years ago, the applicable percentage is twenty percent (20%).
(3) If a plant was placed in service at least forty (40) years ago, the applicable percentage is twenty-five percent (25%).
The time that has expired since a plant was placed in service shall be determined as of the date that an application is filed with the corporation. However, in the case of an industrial recovery site described in section 5(2) of this chapter, the time that has expired since a plant was placed in service shall be determined as of the date on which the demolition of the vacant plant was completed.