Grace Edwards says she discovered the billing error after a prospective buyer for the house in Cheshire asked for a history of utility charges.
Connecticut Light & Power says a developer who previously owned the home had agreed to pay for the lights.
The company initially refused to reimburse Edwards but relented when the state’s Office of Consumer Counsel got involved.
The overcharges amounted to about $35 each month.
CL&P spokesman Mitch Gross says the utility has apologized to Edwards for the error and inconvenience.