JACKSON (AP) — Two of Mississippi’s major electric utilities are charging customers excessive interest rates as part of the state’s fuel adjustment policy and a public hearing is set for Nov. 6 to investigate the practice, regulators say.

The Mississippi Public Service Commission said Tuesday that it discovered the high interest rates during a July review of the policy, which allows utilities to predict the price of the fuel they’ll need to make electricity before actually buying it.

The policy forced customers to pay nearly $40 million too much for their utilities last year, according to the PSC. Customers will eventually get that money back, but the commission has argued that they never should have paid that much in the first place.

The commission says it found that Entergy Mississippi is currently charging a 12.83 percent interest rate in its fuel adjustment, while Mississippi Power Company is charging 13.25 percent.

‘‘There’s not a bank in Mississippi that is giving that kind of interest rate to people who go in and invest their money,’’ Commissioner Brandon Presley said.

Commission Chairman Leonard Bentz noted that utilities in other Southern states charge interest rates of 4 to 6 percent and that the prime lending rate is about 5 percent.

Any change in the rates in Mississippi would effect the amount customers get back after being overcharged or the amount customers will owe the utility after being undercharged, according to Bentz. In recent years, he said, utilities have rarely undercharged customers.

Presley said high interest rates should only be charged when there is a risk that an entity will not get its money back, and he says, the risk for utilities is low in Mississippi.

‘‘There is a statute that authorizes them to get that money back dollar for dollar,’’ Presley said.

‘‘So there isn’t any risk that they’re going to expend it and not get it back. … If you don’t bare much risk, you don’t get much interest, plain old economics.’’

Entergy spokeswoman Mara Hartmann said that historically her company has taken in too little money more often than it has recovered too much under the fuel adjustment policy.

She also said the interest rate was set through a complex formula by the commission, which now has new members, to give utilities a way to recoup the cost of borrowing money when customers are undercharged.

‘‘We are going to comply with whatever they decide,’’ Hartmann said.

Mississippi Power spokeswoman Cindy Duvall says her company is looking forward to the public hearing. ‘‘We respect the authority that the Public Service Commission has and we respect their right to look into these issues. We want them to do whatever they need to do to feel good about our process,’’ Duvall said.

Entergy provides power to 45 of Mississippi’s 82 counties. Entergy operates regulated power utilities in Louisiana, Mississippi, Arkansas and Texas that serve 2.5 million customers and has regulated natural gas businesses in Louisiana.

Mississippi Power Co. serves 23 counties in southeast Mississippi.

‘‘I don’t think that there is any secret that it’s some tough economic times out there,’’ Commissioner Lynn Posey said. ‘‘This is just an ongoing effort on the part of the commission to make sure that our rate payers are being treated fairly.’’