The Maryland Public Service Commission has authorized Delmarva Power to increase electric delivery rates by nearly 4 percent, the utility announced Wednesday.

The increase for Delmarva's Maryland customers is effective for electric service rendered on and after Sept. 15. According to the company's website, Delmarva has 5,342 residential and business customers in northeastern Harford County and 45,007 customers in Cecil County, among 195,000 customers in Maryland.

The rate increase will add 3.6 percent to monthly residential bills, the company said in a news release posted on its website.

A typical bill for a residential customer using 1,000 kilowatt-hours a month would increase by approximately $5.09, moving the average monthly bill from $140.22 to $145.31, or approximately 16 cents more per day, according to the release. The bill's impact on commercial and industrial customers would vary according to usage.

The approval of the $14.98 million revenue increase is less than the company's request for $22.57 million, the release notes.

"While we believe the entire amount of our rate increase request was fully reasonable, the PSC's decision reflects an effort to balance our need for additional revenues to maintain the reliability of our electric system while having a fairly modest effect on our customers," said Gary Stockbridge, Delmarva Power region president. "We will continue to make the necessary investments in our electric system to meet customers' needs and regulatory requirements."

The PSC also approved a Grid Resiliency Charge which amounts to approximately $0.03 cents per month, starting in 2014, for the average residential customer, the company said, explaining that this charge will cover costs associated with Delmarva Power's plans to accelerate its reliability improvements by upgrading key equipment in the next two years.

Delivery rates cover the cost of poles and wires that carry electricity to customers' homes and businesses and are separate from supply rates, the news release notes. Supply rates are determined by wholesale energy markets and reflect the cost of power that Delmarva Power purchases on behalf of its Maryland customers who do not buy power from an alternate supplier. Supply costs are driven primarily by the cost of fuel to make electricity.

Customers who buy electricity from a competing supplier will see the same increase in their delivery rates, Delmarva said.