It's like having a second small fuel tank in your car. You fill it at home by plugging it into the socket at night - and it gives you transportation around town for the equivalent of less than $1 a gallon.

Our goal for the build kit is this summer, but making this happen will be a volunteer project--as are most open-source efforts--so I'm not in a position to promise.

I get about 99 miles to the gallon. When gasoline costs $3 a gallon, driving most gasoline cars costs 8 to 20 cents a mile. With a plug-in hybrid, your local travel and commuting can go down to 2 to 4 cents a mile.

Many hybrid owners realize how sharply fuel efficiency goes down over 55 mph because they get instant mileage feedback.

You're substituting electricity for gasoline - that's the big benefit.

It's wonderful. In about a year, everyone's going to hear about plug-in hybrids.