(a) The commissioner, in granting or denying an exemption under § 16a-13, may take into account past levels of energy consumption or changes therein on the part of the person seeking such exemption.

(b) The commissioner may adopt regulations, in accordance with chapter 54, which establish procedures for documenting past levels of energy consumption or changes therein for the purposes of an exemption under said § 16a-13.

(c) The commissioner may grant an exemption if he determines that the person seeking the exemption has fulfilled the conditions contained in such regulations. The regulations shall permit exemption: (1) In cases where the applicant documents an absolute reduction in energy consumption over such periods of time as the regulations may establish, which periods may vary for different categories of persons, and the reduction is the result of physical or behavioral changes or adjustments undertaken for energy conservation purposes and not from changes or modifications undertaken for other purposes, such as alterations in building size, extent or type of production capacity or utilization thereof, or changes in the nature or number of work force employed, which changes were not undertaken for energy conservation purposes; or (2) in cases where the applicant documents that his consumption of energy is substantially less than that of other persons in like circumstances over such period of time as the regulations may establish, which periods may vary for different categories of persons, and the level of consumption is due to physical or behavioral factors, changes or adjustments, undertaken for energy conservation purposes and not from factors, changes or modifications not so related.

(d) The regulations may provide that reductions in or levels of energy consumption which occur subsequent to the proclamation of an energy emergency pursuant to § 16a-11 or § 16a-12 shall not constitute the basis for exemption unless the reductions are due solely to actions undertaken prior to such proclamation.