DONOFRIO, J.

In these consolidated cases, appellants, the Association of Businesses Advocating Tariff Equity (ABATE) and the Michigan Attorney General, appeal as of right an order of the Michigan Public Service Commission (PSC) that allowed petitioner, Michigan Consolidated Gas Company (Mich. Con), to include through charges applied to its ratepayers more than $5 million in funding for the Low-Income and Energy Efficiency Fund (LIEEF). The Attorney General additionally appeals that part of the order that allowed Mich. Con to continue to use an uncollectible expense true-up, or tracking, mechanism (UETM) as a way to reconcile recovery of estimated and actual losses stemming from customers who fail to pay their bills. We affirm the PSC's decision to allow Mich. Con to continue using its UETM, but reverse the PSC's decision to allow Mich. Con to charge its ratepayers for funding of the Low-Income and Energy Efficiency Fund.

I. FACTS

The PSC's opinion and order in this case contains the following concise statement of the facts:

The PSC approved the continued use of the UETM intended to adjust future rates to make up for 80 percent of the difference between Mich. Con's estimated and actual burdens in connection with customers from whom it could not collect amounts due on their bills, approved a base level of uncollectible expenses of $69.9 million, and rejected the Attorney General's objections that such tracking mechanisms are not statutorily authorized. The PSC also approved $5,069,000 in test-year funding for the LIEEF and rejected appellants' objections that the Legislature had repealed the legislation authorizing such funding in the first instance.

This appeal followed.

II. STANDARDS OF REVIEW

All rates, fares, charges, classifications, joint rates, regulations, practices, and services prescribed by the PSC are presumed prima facie to be lawful and reasonable. MCL 462.25; see also Mich. Consol. Gas Co. v. Pub. Serv. Comm., 389 Mich. 624, 635-636, 209 N.W.2d 210 (1973). A party aggrieved by an order of the PSC has the burden of showing by clear and satisfactory evidence that the order is unlawful or unreasonable. MCL 462.26(8). To establish that a PSC order is unlawful, the appellant must show that the PSC failed to follow a statutory requirement or abused its discretion in the exercise of its judgment. In re MCI Telecom. Complaint, 460 Mich. 396, 427, 596 N.W.2d 164 (1999).

A final order of the PSC must be authorized by law and supported by competent, material, and substantial evidence on the whole record. Const. 1963, art. 6, § 28; In re Consumers Energy Co., 279 Mich.App. 180, 188, 756 N.W.2d 253 (2008). A reviewing court gives due deference to the PSC's administrative expertise and is not to substitute its judgment for that of the PSC. Attorney General v. Pub. Serv. Comm. No. 2, 237 Mich.App. 82, 88, 602 N.W.2d 225 (1999).

Issues of statutory interpretation are reviewed de novo. In re Rovas Complaint Against SBC Mich., 482 Mich. 90, 102, 754 N.W.2d 259 (2008). A reviewing court should give an administrative agency's interpretation of statutes it is obliged to execute respectful consideration, but not deference. Id. at 108, 754 N.W.2d 259.

Whether the PSC exceeded the scope of its authority is a question of law that is reviewed de novo. In re Pelland Complaint Against Ameritech Mich., 254 Mich.App. 675, 682, 658 N.W.2d 849 (2003).

III. UNCOLLECTIBLE EXPENSE TRUE-UP MECHANISM

The UETM addresses the utility's burden in supplying power to customers from whom it cannot collect.2 Mich. Con sought to change its base level of uncollectible expenses from $37.3 million to $69.9 million to reflect its recent experience with increasing numbers of customers from whom it could not collect. Mich. Con had been using its UETM to ensure its recovery of 90 percent of unpaid bills—less than 100 percent so that the utility would retain an incentive to expend efforts to collect from its customers. However, the hearing referee proposed adjusting that recovery rate to 80 percent on the ground that Mich. Con had shown something less than due diligence in the matter. The PSC accepted the higher figure for the base rate of uncollectible expenses and accordingly approved a continuation of the UETM, while adopting the referee's recommendation to shift Mich. Con's risk factor from 90 to 80 percent. It is not in dispute that all cost-tracker mechanisms operate by comparing actual revenues to the base revenues approved by the PSC for the purpose of adjusting future rates to compensate for the differences.

Retroactive ratemaking in utility cases is prohibited, absent statutory authorization. Mich. Bell Tel. Co. v. Pub. Serv. Comm., 315 Mich. 533, 547, 554-555, 24 N.W.2d 200 (1946). The Attorney General argues that use of the challenged tracking mechanism runs afoul of that principle. But retroactive ratemaking does not occur if only future rates are affected, with no adjustment to previously set rates. Attorney General v. Pub. Serv. Comm., 262 Mich.App. 649, 655, 658, 686 N.W.2d 804 (2004).

This Court recently reiterated its approval of the PSC's use of the accounting convention whereby certain expenses dating from one year are characterized as expenses incurred in a subsequent year to which they are then deferred. In re Consumers Energy Co. Application for Rate Increase, 291 Mich.App. 106, 114, 804. N.W.2d 574 (2010), citing Attorney General, 262 Mich.App. at 658, 686 N.W.2d 804.

This Court has specifically approved Mich. Con's use of a UETM on the ground that

This weight of authority compels affirmance of the PSC's approval of Mich. Con's use of the UETM.

IV. THE LOW-INCOME AND ENERGY EFFICIENCY FUND

The Customer Choice and Electricity Reliability Act, MCL 460.10 et seq., was enacted by 2000 PA 141, with an effective date of June 5, 2000. Consumers Energy, 279 Mich.App. at 182-183, 756 N.W.2d 253. The act in part created the LIEEF, the purpose of which was "`to provide shut-off and other protection for low-income customers and to promote energy efficiency by all customer classes.'" Id. at 183, 756 N.W.2d 253, quoting MCL 460.10d(7).

As originally enacted, MCL 460.10d(6)— redesignated as MCL 460.10d(7) by 2002 PA 609-required the PSC to "establish standards for the use of the [LIEEF]...." See also In re Consumers Energy, 279 Mich.App. at 190, 756 N.W.2d 253. That subsection further commanded the PSC to "issue a report to the legislature and the governor every 2 years regarding the effectiveness of the fund." Former MCL 460.10d(6). The subsection also provided for funding the LIEEF through "securitization savings exceed[ing] the amount needed to achieve a 5% rate reduction for all customers ... for a period of 6 years," id., but this Court has declared that the latter provision did not limit the PSC's options for funding the LIEEF after the running of that six-year period, Consumers Energy, 279 Mich.App. at 191, 756 N.W.2d 253. However, MCL 460.10d was amended by 2008 PA 286, effective October 6, 2008, with the result that the Customer Choice and Electricity Reliability Act no longer refers to a LIEEF. Appellants assert that the legislative debates attendant on the enactment of the 2008 legislation included a proposal to authorize a LIEEF factor and extend LIEEF requirements to all Michigan utilities, but this proposal did not win passage.

Yet MCL 460.9p(3), added by 2009 PA 172, effective December 15, 2009, directs that civil fines assessed against municipally owned electric or natural gas utilities be deposited "in the low income and energy efficiency fund." And the appropriations act that appropriated funds for the PSC for the 2009-2010 fiscal year, 2009 PA 130, included provisions for the LIEEF. In particular, § 114 of the act listed an appropriation of $90 million for "[l]ow-income energy efficiency assistance," along with one for the same amount for "[l]ow-income energy efficiency fund[.]" Section 361(1) of the act in turn called upon the PSC to "implement a process for the low-income energy efficiency fund grants that shall require an application deadline of May 1 and the award announcements on October 1 of each year," while § 361(2) required the PSC to "report by November 1, 2009 to the subcommittees, the state budget office, and the fiscal agencies on the distribution of funds appropriated in part 1 [of the act] for the low-income/energy efficiency assistance program."

If this recent legislative activity indicates the Legislature's intention that the LIEEF continue to exist, and that the PSC retain some role in managing it, the deletion of all references to the LIEEF from the Customer Choice and Electricity Reliability Act—whose now-deleted provisions were recognized as the fund's enabling legislation in the first instance, see Consumers Energy, 279 Mich.App. at 183, 756 N.W.2d 253—nonetheless indicates a legislative intent to withdraw any obligation, or prerogative, on the part of PSC-regulated utilities to raise money for that fund. See Ford Motor Co. v. Unemployment Compensation Comm., 316 Mich. 468, 473, 25 N.W.2d 586 (1947) ("The court is not at liberty to read into the statute provisions which the legislature did not see fit to incorporate, nor may it enlarge the scope of its provisions by an unwarranted interpretation of the language used.").

Moreover, while MCL 460.6a(2) grants the PSC authority to establish procedures for considering and deciding petitions from regulated utilities and allow a utility to recover its reasonably and prudently incurred costs, it does not grant the PSC authority to approve a utility's collecting funds from its ratepayers in general to fund a program designed to offer some protection against interruptions in services, or other such relief, to distressed ratepayers. That activity has less to do with regulating a utility than with helping the poor. Similarly, a program to promote energy efficiency in general has more to do with environmentalism and conservation than with assessing a utility's reasonably and prudently incurred costs.

For these reasons, we hold that administration of a LIEEF does not fall within the scope of the PSC's general statutory powers, but depends in every instance on specific statutory authorization. Accordingly, we reverse the PSC's order below insofar as it approved more than $5 million in LIEEF funding to come from Mich. Con's ratepayers and remand this case to the PSC for appropriate proceedings consistent with this opinion with respect to the LIEEF, and any remaining implementation regarding the UETM.

Affirmed in part, reversed in part, and remanded for further proceedings. We do not retain jurisdiction. Because no party has prevailed in full, we do not award costs pursuant to MCR 7.219.

SAAD, P.J., and JANSEN, J., concurred with DONOFRIO, J.