Delmarva Power & Light Co. must defend itself against challenges to its formula transmission rate filings for 2011 and 2012, the Federal Energy Regulatory Commission ruled last week.

FERC unanimously rejected Delmarva’s claim that the challenges by municipal power agencies and electric cooperatives were impermissible on procedural grounds, though the commission did narrow the issues to be litigated.

The commission ordered a hearing on whether Delmarva’s filings are consistent with FERC rules regarding accounting for income taxes and whether it properly allocated expenses from its parent, Pepco Holdings, Inc. It encouraged the parties — which include Delaware Municipal Electric Corporation, Inc. (DEMEC), Easton Utilities, Old Dominion Electric Cooperative and the Public Power Association of New Jersey — to settle the issues before the hearing.

DEMEC contends that Delmarva has added new costs that were not included in its initial formula rate and that the company improperly booked some non-transmission expenses. The protestors also complained about an increase in Delmarva’s administrative & general costs since implementation of the formula rate.

The commission rejected Delmarva’s contention that that the terms of a 2006 settlement (Baltimore Gas and Electric Co., 115 FERC 61,066) do not permit prudence challenges and that the formula rate inquiry is limited to whether costs were booked to the correct account.

“The commission’s acceptance of a formula rate constitutes acceptance of the formula, but not the inputs to the formula,” the commission wrote. “Parties can challenge the inputs to the formula rate in the same way as they can challenge costs in a stated rate case, including by raising prudence issues. In order for formula rates to work properly, they must allow for after-the-fact corrections and updates.”

The commission dismissed challenges to Delmarva’s handling of taxes associated with deferred investment tax credits and non-deductible pensions and other benefits.

FERC also rejected DEMEC’s request to reduce Delmarva’s return on equity, saying that it was outside the scope of issues permitted in challenges to annual rate filings. The panel noted that DEMEC and the Delaware Consumer Advocate’s office are contesting the ROE in a separate challenge before the commission (EL13-48).