Mendocino County supervisors have formalized their intent to join public supplier Sonoma Clean Power in a bid to offer greener, cheaper electricity options to county residents.

More than 30,000 residential and commercial customers could be offered a choice between PG&E, the county’s dominant electricity supplier, and Sonoma Clean power by early next summer if things go as planned, said Christopher Shaver, Mendocino County deputy chief executive office.

The next step is for Sonoma Clean Power to grant Mendocino County membership. Its board already voted in early July to offer services in Mendocino County and several of its cities, excluding Ukiah, which has its own electric utility.

Mendocino County supervisors this week unanimously adopted a resolution stating their intent to join Sonoma Clean Power.

“I think this is a great opportunity,” said Supervisor Dan Hamburg.

While it’s expected to save residents money on their bills — Sonoma Clean Power officials claim to have saved Sonoma County customers more than $62 million since it launched in May 2014 — the transition was billed more importantly as a step toward reducing greenhouse emissions, supervisors and supporters said.

The agency’s basic service has an energy supply that is 36 percent renewable, from geothermal and wind sources. Contracts for solar projects have been signed, with construction underway on installations inside Sonoma County and outside the area.

PG&E’s basic service is 27 percent renewable. Under state rules the utility’s supply from large hydroelectric projects does not qualify as renewable.

Cities and counties throughout the state have been considering so-called “community choice aggregation” agencies like Sonoma Clean Power since they were authorized by state law in 2002. Marin County launched the first such program, Marin Clean Energy in 2008.

Lake County officials also are exploring energy options.

Once Mendocino County officially joins Sonoma Clean Power, customers in the unincorporated county will automatically become its consumers unless they take action to opt out. The eligible cities — Fort Bragg, Point Arena and Willits — will first need to join the agency before consumers in their jurisdiction are enrolled, with the same choice to opt-out.

Bills will continue to be sent by PG&E, which also will continue to own, maintain and operate the transmission system.

Sonoma Clean Power and similar ventures largely search out and buy power on the wholesale energy market.

The agency serves 196,000 residential and commercial accounts in Sonoma County, representing about 89 percent of eligible electricity customers.