Green power will cost you some green

San Francisco is about to find out how much it costs to be clean and green. After years of study and initial approvals, city residents will learn the price of a new energy diet, one that promises electricity from only renewable sources.

The plan, known as CleanPowerSF, won support from city supervisors and appears on track to win backing from the city Public Utilities Commission, which will oversee it. Then it will be time to test bigger questions. Will customers join a program whose costs are rising, with rules that seemed skewed and the chance that the city will be left holding the bag?

The program comes with ample appeal. Most customers are aware that renewable energy from solar, wind and biofuels is more expensive. A poll by the city showed that 47 percent would pay extra for renewable power, a level of support that may get the plan off the ground.

But the cost of renewable power won't be known until contracts are signed, an uncertainty that city officials are trying to rein in by imposing ceiling prices to be devised in coming weeks.

The program comes with a feature that's consumer-unfriendly. Under terms of a state law that allowed cities and counties to set up energy-buying programs, customers are automatically enrolled unless they opt out. It was created to give a fledging idea an instant constituency, but it puts the onus on customers to protect their wallets.

This is the wrong approach. The default position should be that customers stay with PG&E unless they choose to make a change.

There is a reason San Francisco is stacking the deck for this new scheme. If the city can't keep roughly a quarter of available homes and businesses enrolled, it will need to make up the difference or risk losing $13.5 million under a contract with Shell Energy, the only bidder.

Beginning this month, the city is rolling out a $1.4 million publicity campaign to explain the options and advantages of the program. It needs to counteract a noisy push by the electrical workers union, which opposes the renewable plan because its members believe it doesn't guarantee the power will come from unionized sources.

San Francisco wants to be in front on issues involving technology, green energy and climate change. If it really can deliver what it promises at a reasonable price, then it should have no trouble persuading consumers to opt in.

A risky scheme

Here are the key advantages and drawbacks to the city's CleanPowerSF program:
PRO

-- Customers can buy 100 percent renewable power. PG&E's power is now 19 percent renewable.

-- The city plan offers customers an outside option to PG&E.

-- The city's risk is limited to $13.5 million if plans go awry.
CON

-- Average electric bills will rise. The city says most users will pay between $10 and $20 more each month.

-- Customers must opt out or they will be enrolled automatically

-- The city needs 90,000 customers out of 380,000 households to break even.