BOSTON >> Electric and natural gas utility NStar has agreed to refund its customers almost $45 million for overcharges on capital improvements, pension expenses, and energy efficiency programs.

The agreement announced Wednesday resolves 11 cases before Massachusetts utilities regulators.

The state attorney general’s office says the utility collected the surcharges, but no timely reviews were conducted to determine whether they were excessive.

The settlement is subject to approval by the state Department of Public Utilities by an agreed upon deadline of March 2.

Customers should see rate reductions on their bills after the settlement is approved.

The exact amount coming back to each customer has not been determined.

NStar has 1.1 million electric customers and 300,000 gas customers in Massachusetts.