PROVIDENCE, R.I. (AP) — National Grid wants to increase its distribution rates for electric and gas customers in Rhode Island, which would cause bills to rise next year.

The utility filed the proposal Monday with the state Public Utilities Commission. The hike in base distribution rates would be the National Grid's first since 2012. Residential electric bills would rise by 6 percent and gas bills would increase by 5 percent.

Any approved rates wouldn't be effective until Sept. 1, 2018.

President Tim Horan says resetting the rates allows the utility to "continue to improve service quality."

Democratic Gov. Gina Raimondo said Monday families and small business owners already face high energy costs, and called on the Public Utilities Commission to "open up National Grid's books."

Democratic Rhode Island U.S. Rep. David Cicilline called the proposed rate hike "unacceptable."