1. The amount of the adjustment must:
(a) Permit the applicant to recover the cost of the conversion, net of any taxes which may be imposed on the applicant for revenue received because of the adjustment, within the period of recovery authorized by the Commission.
(b) Be at least two-thirds, but not more than three-fourths, of the cost of the fuel saved.
2. The Commission shall not recognize, when calculating any rate, price or charge, other than the amount of the adjustment, the costs of the conversion subject to the requirements of this section.