As part of his green energy plan, newly inaugurated U.S. president Barack Obama wants to see one million plug-in vehicles on the road in the next seven years.

The conversion will boost mileage dramatically, and conversion kits are already available to turn a Toyota Prius into a plug-in.

It's expensive, but Consumer Reports wanted to test to see what the future is going to bring.

Prius owner Lee-Ann Mercando says she would be happy to convert her vehicle.

"That would be fantastic," she says. "I would love it. Anything to get better gas mileage these days."

Now you can have a lithium-ion battery installed in your Prius, plug it in at night, and do just that.

The batteries are like a really big laptop battery. They're put in the wheel well where your spare tire normally goes and a small hole has to be made for the plug.

Tests found the plug-in Prius did not routinely get the fuel economy claimed, but still found the plug-in kits really boosted mileage.

Consumer Reports tests show that the fuel efficiency improved by almost 60 per cent.

You may wonder why it uses any fuel at all. That's because the Prius cycles the gasoline engine on and off to keep it warm for when it's needed and to provide heat in the winter.

But if you're ready to convert your Prius, you might be forced to wait.

"You can't do this installation yourself and there are only a handful of locations that are authorized to do the conversion," says Consumer Reports' Jon Linkoz. "We had to wait five months to get our kit installed."

And then there's the matter of the money -- converting the Prius to a plug-in costs more than $10,000.

"From a dollars-and-cents perspective, doing this conversion makes no sense because it would take decades to recoup the cost," says Linkov. "But the plug-in technology is a viable option if it becomes massed produced and costs come down."

In the meantime, tests show a Prius like Lee-Ann's is one of the best money-saving, fuel-saving deals on the road.

Several other plug-ins are planned, including the Chevrolet Volt that General Motors says comes out next year.

The plug-in Prius ran 55 kilometres before the battery ran down. When you consider a majority of people drive little more than that a day, a plug-in car could dramatically cut fuel consumption.

With a report by CTV British Columbia's Chris Olsen