Peco has asked federal regulators to approve a $21.7 million increase in its transmission charge, which would boost a typical residential customer's monthly bill by 29 cents, or 0.3 percent. The increase would cost small business customers about $1.78 more a month, and the largest industrial customers about $76 more per month.

Philadelphia-based Peco filed papers Monday with the Federal Energy Regulatory Commission to pay for the cost of the high-voltage system that transmits electricity from power plants to the local distribution system. The charge is typically included in the commodity charge, or "price to compare," and not broken out separately on bills.

Peco says it it needs a higher rate to maintain the transmission system, which is carrying less power because of energy efficiency and load-shifting to off-peak hours. The $21.7 million increase would boost revenue 12.4 percent, to $196.8 million.

"Peco is submitting this filing because its existing rates, set almost two decades ago, fail to recover Peco's costs – a situation that will only get worse if, as projected, Peco's transmission costs rise and its transmission load declines," the company said in its filing.

The utility also is asking FERC to approve a new formula for adjusting the transmission charge annually to allow for more immediate recovery of its investments. The formula has been adopted by most other utilities that are members of the regional grid operated by PJM Interconnection, Peco said.

The complete 1,127-page filing is available on PJM's website.