PALO ALTO, Calif. - With the backdrop of a nation caught in the grip of skyrocketing fuel prices, a San Carlos, Calif., auto repair shop is trying to convert Toyota Priuses and possibly other hybrids to plug-ins that could be charged overnight through a standard outlet and get even better gas mileage.

Eric Sevim, a co-owner of A + Japanese Auto Repair with his brother Adam, said he wants to start converting hybrids by mid-August. Experts in the field have called his plans ambitious, but Sevim says his research the past year convinces him it can be done if he makes the right contacts.

"I wouldn't say the gas prices are the first motivation. The first motivation is to be green," Sevim said. "We are doing everything in our power to promote efficient vehicles."

The shop is looking at installing the most proven system available, A123 Systems, which has been crash-tested and certified, or Energy CS, which is a design that Pacific Gas & Electric is testing. But other kits available can be installed on a car.

"What is nice about it, it is just simply a (lithium ion) battery pack and there is no additional maintenance," Sevim said.

Pat's Garage in San Francisco has installed the A123 Systems plug-in conversion on Google vehicles and other companies' cars. It is available nationwide at six places, four of them Toyota dealers.

"It is just now entering sort of the public arena," said Pat Cadam, owner of Pat's Garage. "For the past couple of years we have been doing the beta testing. We are going to start selling to the public."

Cadam said he would not be opposed to other repair shops in the area offering the A123 System because his shop played a pivotal role in developing it, and his goal is to get as many of the plug-ins on the streets as possible.

Already, 150 people have lined up to have their Priuses converted to plug-ins before the end of the year at Pat's Garage.

The conversion would boost a Prius' gas mileage from 40-45 miles per gallon to 70-90 mpg. However, with a price tag of $10,400, the plug-in system is not for people who simply want to save money at the pump. Rather, it's for those who want to go green and be the first to have it done, Cadam said.

"Until the car makers are mass producing the cars, you are not going to save money because the conversions are expensive," said Felix Kramer, founder of the Palo Alto-based California Cars Initiative, a nonprofit that advocates for plug-ins.

Kramer was in Washington D.C., recently at a conference sponsored by Google and the Brookings Institution called "Plug-In Electric Vehicles 2008: What Role for Washington?"

He claims to have done the first conversion on a Prius in 2004. There are only 150 such vehicles in the world, he said.

"It gives you the cleanest extended-range vehicle," Kramer said.

PG&E officials said they have found other benefits beyond greenness and fewer fill-ups. The utility has been testing since 2006 a plug-in Prius that uses the Energy CS-designed system. They boast that their plug-in gets 100 miles per gallon for a typical commute of about 20 to 40 miles round trip to work.

"The purpose for us to do it was to research plug-in electric vehicles and see if there are any grid benefits," said Jennifer Zerwer, a PG&E environmental news representative. "We were the first utility to demonstrate the ability of the plug-ins to feed energy back to the grid."

The utility has also shown it could run lights and fans with the plug-ins by attaching a power inverter to the system and flipping a switch, Zerwer said.

PG&E partnered with Tesla Motors in San Carlos, which produces an all-electric $100,000 sports car, on what the companies call smart charging. The technology would allow the car being plugged in to communicate with the power grid, so someone could plug their hybrid in when he or she gets home from work, but the car would not get the OK to start charging until after midnight, when electricity usage declines.

PG&E envisions a day when people can drive to work in their plug-ins, recharge there and the utility could e-mail the vehicle's owner to ask if the power company could buy electricity if there's high demand that day, Zerwer said.

"Certainly the response we got from our customers is it is something they are interested in," she said about the plug-ins.