IMAGINE a car that powers your home during a blackout. Or one that produces so much extra energy, the utility company pays you.

Stop imagining.

Pacific Gas & Electric Co., joining a growing number of advocates for plug-in hybrid cars, showcased a converted Toyota Prius at an alternative energy gathering in Sunnyvale on Monday. The investor-owned utility, which appears to be the first in the United States to demonstrate a car that can power a home, says customers will be able to use plug-ins to cut greenhouse gas emissions as well as high home-energy bills.

"If there has ever been a place to start and capture the possibilities and imagination of consumers, California is the place," said Bob Howard, PG&E vice president of gas transmission and distribution.

While sales of conventional hybrids such as the Toyota Prius that run on a combination of electric and gasoline motors have skyrocketed the past few years, major automakers have been reluctant to build mass-market plug-in hybrid vehicles, which can be recharged with a home's electrical outlet. They said consumers weren't interested because the cars would be too expensive.

But as manufacturing prices have dropped and gas prices have risen, attitudes have shifted.

"We have a race going on between the carmakers," said Felix Kramer, founder of CalCars and a guru in the plug-in hybrid industry. "It's a complete change from a few years ago, when everybody said nobody wants this."

A study by the Palo Alto-based nonprofit Electric Power Research Institute projected that if gas prices nationwide hovered near $3 a gallon and electricity costs averaged 8.5 cents per kilowatt-hour, plug-in hybrids make more economic sense than conventional cars. Average gas prices are $3.40 a gallon in the San FranciscoSan Mateo area, $3.29 in the East Bay and $3.28 in the San Jose area. And PG&E said its plug-in hybrid costs 2 to 4 cents per mile to operate, compared with a typical car that costs 8 to 20 cents per mile.

(PAI - MediaNews; Source: Pacific Gas & Electric, Toyota)

San Francisco-based PG&E, which uses more renewable energy than most utilities in the nation, must continue to increase its use of renewable energy sources such as wind and solar to meet aggressive global warming goals passed by lawmakers the past few years. Plug-ins help that goal, the company said, because they enable homeowners to use more energy at night — when wind and other cleaner fuels are available — and less energy during high-demand days, when it's more likely natural gas and coal plants that produce carbon are providing energy.

Most of the major automakers, from Toyota to Ford, have also felt pressure to cut carbon emissions that take a toll on the environment. Last year, General Motors became the first manufacturer to pledge that it would market a plug-in hybrid, while the others have said they are considering it. GM spokesman Jeff Holland said Friday that its Saturn Vue sport-utility vehicle will be available as a plug-in by the end of 2009. He couldn't say how much it would cost.

Prices for plug-in hybrids are expected to range from $3,000 to $5,000 more than conventional hybrids, which would mean cars such as the Toyota Prius would be in the high $20,000 price range, said Bill Van Amburg, senior vice president for the industry trade group CALSTART.

The small number of plug-ins on the road today are custom-converted vehicles, much like PG&E's tricked-out Prius.

PG&E's conversion, done by EnergyCS, cost $40,000. The car's lithium battery, which takes up the bottom of the back trunk where a tire would go, adds an extra 180 pounds to the car's weight. It produces 9 kilowatts of electricity; the average house uses about 2.5 kilowatts of electricity an hour.

Like a traditional hybrid, plug-ins have both electric motors and batteries as well as a gasoline engine. The gas engine kicks in when the car is moving about 20 to 25 miles per hour.

A 2007 Toyota Prius gets 55 miles per gallon in combined city and highway driving, according to a government report late last year. But a plug-in hybrid has a bigger battery, allowing it to use the gasoline engine less and reach 100 mpg. 

Most hybrid plug-in prototypes simply take energy from a home's electricity outlet. But a growing number of engineers, including those at PG&E, say any plug-in can also be used as a two-way generator.

These so-called vehicle-to-grid, or V2G, cars charge by plugging into a three-prong 110- to 120-volt outlet. If the home needs energy, such as during a blackout or on a peak day when electricity prices are high, a switch can be flipped to send the charge the other way.

It's unclear how much money a homeowner would save on energy costs using a plug-in hybrid. To be sure, consumers would buy more electricity from the utility, but they would probably cut their gasoline bills.

PG&E hopes the concept car will show consumers new ways to use hybrids, thus increasing consumer demand.

During a demonstration Friday, the PG&E car powered a small electric heater and lights. If needed, the car could run home appliances for several hours after being charged all night.

PG&E said it would like to pay consumers a credit for extra energy the car's battery sent back onto the state's electricity grid, the same way the utility pays credits to solar homeowners who feed energy back into the grid. That would need approval from regulators.

Contact Sarah Jane Tribble at stribble@mercurynews.com or (408) 278-3499.