Green power for Marin is a concept that has merit along with a loyal and growing fan base. But before the concept becomes a reality, it needs broad public support.

The best way to prove that support is with the validation of a countywide vote.

County officials are soon likely to propose a joint power authority for Marin. This new governmental entity would supply residents and businesses with electricity from renewable sources.

A state program called "community choice aggregation" allows municipalities to go into the power business. In Marin, Pacific Gas & Electric would still deliver the electricity and maintain the lines, but a county power authority would contract with power suppliers.

Marin is one of the pioneers in community choice aggregation. The county proposal, which has been in the study stage for years, is focused on delivering green power, not just saving customers' money.

Advocates say two levels of green power would be offered. The first would cost about the same as PG&E power and offer electricity that is up to 50 percent from renewable sources, such as wind and solar. The second tier would be 100 percent green and cost slightly more than PG&E. The county say surveys have indicated 58 percent of residents are willing to pay 10 percent more for green power.

One important caveat: While the local authority would sign contracts with green power suppliers, there is no way to promise that green juice actually flows to homes in Marin. Once electricity is added to the grid, it all gets mixed together - like water in a reservoir fed by many streams.

Most of Marin's green power would be generated outside Marin. What the local power authority is actually doing is increasing the demand for green energy, which will, in turn, lead to increases in the supply of green power. At least that's the theory.

Here's how the deal would play out:

- The county Board of Supervisors and the councils of Marin's 11 cities and towns would vote separately on whether to join a new joint authority.

- To move forward, cities representing at least half of Marin's energy use must take part. Areas that don't join won't provide customers for the new power authority.

- An outside vendor would be hired to obtain the power.

Green power is a good idea, but we are troubled by one aspect of the proposal.

The enabling state law only allows residents and businesses to opt out of the program. In other words, if your city council decides to participate, you are automatically part of the program unless you fill out paperwork to stay with PG&E power.

Experts say the law was written that way because if users were required to join - opt-in - too few customers would make the switch. County officials backing the plan promise there will be aggressive education and outreach efforts to let people know what is coming before they are switched.

We prefer an opt-in approach, but it is not permitted under current law.

To make sure residents make an informed and conscious choice, we believe the county should put an advisory measure on the ballot to gauge support for a green power authority.

A countywide vote would accomplish two things:

- It would give every city and town council member and county supervisor a clear idea of how their constituents feel about the proposal. This is important: Our elected officials will be asked to vote to have their city or town join the power authority. If they vote yes, they are making an economic decision that would affect every resident and business. That is a lot to ask of an elected official. A clear mandate from a countywide election would make their "yes" votes much easier to cast.

- A countywide election campaign would help educate residents about the power plan. Letting people know as much as possible is vital. Getting the message out will be difficult. One obstacle is inertia. How many people take a close look at the information that comes with their monthly utility bills? And for tens of thousands of county residents, there is a language barrier that must be overcome.

November is the ideal time for an advisory measure. That election could have a record turnout in Marin, thanks to the presidential race.

A high turnout will give strong evidence of voters' positions on the power issue.

The green power proposal isn't just about green power. It also is about good government that listens to its constituents and acts on their behalf and with their knowledge and support.

We urge county officials and green power supporters to put an advisory initiative on the November ballot.