CHESAPEAKE, Va. (AP) — A state prison in Chesapeake says it’s using solar panels to cut down on propane costs.

The Virginia Department of Corrections says solar panel systems have been placed on the rooftop of the St. Brides Correctional Center’s housing units and kitchen.

The panels are being used to heat up ground water before it enters the building’s internal supply system. Officials say that means they don’t have to use as much propane to make the water hot enough for showers, kitchens and bathrooms.

Brian Newbern is buildings and grounds superintendent at the prison. He says in a statement that the project is saving the state around $35,000 a year in propane.

The corrections department says the project was fully funded with grants.