Synergy North says has overcharged about 47,000 of it's customers a small amount for the past four years.
The overpayment amounts to about $0.36 for the average customer.
The utility company, which provides electricity in Kenora and Thunder Bay, adds that many of the people affected are no longer customers of Synergy North.
The company says it notified the Ontario Energy Board when it discovered the billing error.
As a result, Synergy North says it will contribute $20,276 to the Low-income Energy Assistance Program to help customers in need in the service area.
The company adds that it has also corrected the billing error.