In this Aug. 15, 2016, file photo, three wind turbines stand in the water off Block Island, Rhode Island. Credit: Michael Dwyer / AP

A Maine official who is responsible for representing the interests of utility consumers has voiced concerns that an offshore wind electricity supply contract could add to residents’ power bills.

The developers of the offshore wind research array want Maine to approve a 20-year electricity supply contract. Backers of the proposal have described it as integral to Maine’s renewable energy goals.

Public Advocate William Harwood said this week that it’s possible the contract could increase bills if the proposed price is far above wholesale market rates, the Portland Press Herald reported.

Details of the contract are not publicly available yet. The developers of the project could potentially build it by 2028.

Pine Tree Offshore Wind filed papers about the project last month. That group is an affiliate of New England Aqua Ventus, which is in the process of building a demonstration turbine off Maine that would be able to power 5,000 Maine homes annually.

The Mills administration also is working with University of Maine and New England Aqua Ventus on a research array that could contain 10 offshore wind turbines.

Lobster fishermen have voiced concerns that the offshore project could disrupt their industry. The Mills administration has prohibited wind projects in state waters, where most lobster fishing occurs.