DOVER — Delmarva Power is currently issuing credits to about 74,000 customers after the discovery of a billing mistake.



Residential customers will on average receive a $15 credit, according to the company. Refunds are being issued this week.



“Delmarva Power realized a billing error that affected some customers who were assessed late payment charges. Actions to correct the error are already underway,” Delmarva Power said in a statement.

“Affected customers in Delaware and Maryland will receive a credit for the inadvertent additional charges, and interest from when that charge occurred. Delmarva Power regrets the error and is working closely with both the affected customers and program administrators to ensure this error cannot occur again.”



About 45,400 impacted consumers are in Delaware, with the rest in Maryland.

Delmarva Power spokesman Timothy Stokes wrote in an email the company has “high confidence that this is a unique situation.”



He was unsure of the amount of the largest refund Delmarva Power is giving out.



According to the Delaware Division of the Public Advocate, which represents the public’s interest in utility matters, the refund was spurred by a complaint from a Delaware woman.



The woman, a resident of New Castle County, called the division to inquire about her bill, leading to staff noticing various late payment charges. After the division contacted Delmarva Power, the company reviewed its files and concluded thousands of customers were due refunds, with some cases dating back four years.



“This goes to show how important it is to not only pay your utility bills promptly, but to review and understand your billing statements,” Public Advocate Drew Slater said in a statement. “The old adage that one person can make a difference rings true in this case. Had this customer not contacted our office and shared her concern, an issue affecting thousands of households may have gone unnoticed.”



Delmarva Power provides electricity to about 321,000 people in Delaware and 206,000 individuals in Maryland. It also supplies natural gas to 134,000 natural gas delivery customers in northern New Castle County.



Incorporated in 1909, it is currently owned by Exelon.