PETITION FOR REHEARING

United’s petition for rehearing alleges some confusion among the parties because of the wording of the ordering paragraph of our previous opinion. Our reversal vacates the orders of the Commission which were the basis of the appeal.

We note that said Orders of the Commission were based on facts and figures at December 31, 1975 and for the test year ended that date, with adjustments for “known, fixed and measurable changes” that would occur within 12 months after December 31, 1975 (24 months for property taxes). Those facts and figures are now nearly 4% years old. In further proceedings before the Commission the further use of the evidence relating to said “test year”, 1975, would now be subject to serious ques*1269tion of practical materiality upon reintroduction, unless stipulated,' and thus the further proceedings might well include dismissal of the 1975 petition by United, at its option. Although the Commission, not this Court, has the expertise and the jurisdiction to fix the reasonable rates and charges that a utility may charge and collect, the applicable statute and case law requires the Commission to fix rates and charges prospectively, not retroactively.

In all other respects United’s petition for rehearing is denied.