The conversions aren't cheap, and top-of-the-line kits with lithium-ion batteries can set you back as much as $35,000. Even a kit with lead-acid batteries — the type under the hood of the car you drive now — starts at five grand. That explains why most converted plug-ins are in the motor pools of places like Southern California Edison and the National Renewable Energy Laboratory. No more than 150 or so belong to people like Gannett, who had her $30,000 Ford Escape converted in December. Yes, that's right. The conversion cost more than the truck.

"They are crazy expensive right now," Gannett says of conversions, "but the goal is to inspire people by showing them what's actually possible. People have had enough preaching. They need real live examples."

Advocates expect more people to jump on the plug-in bandwagon as the cost of the kits come down. They argue there will be loads of used hybrids just waiting to be plugged in once the Volt and plug-in Prius push the technology into the mainstream. "The combination of gas and electric technology is a happy medium for getting us off of oil and appeasing those who need to travel long distances," says Protheroe. "Until batteries get good enough where you don't need the assistance of an internal combustion engine, plug-ins will become the dominant mode of technology for pushing cars around.”

For all their high-tech allure, conversions are straightforward and a decent shop can do the job in an afternoon. In many cases, it's a relatively simple matter of swapping the car's nickel-metal hydride battery for a lead acid or lithium-ion pack and installing the electronics needed to charge it from a wall socket. The kits add anywhere from 75 to 360 pounds to the car, depending on battery type, and some of them require ditching the spare tire.

The second-gen Prius is by far the most common car for the switch, but companies like Hybrids Plus will do the job on Ford Escape hybrids, and ConVerdant Vehicles has a kit for many of the pickups and SUVs Detroit's been cranking out for the better part of 20 years.

It wasn't all that long ago that converting your car meant rolling up your sleeves and setting to work, a task made somewhat easier with the help of California non profit CalCars (credited with the very first conversion) and the PriusPlus open-source wiki. But theses days shops like Advanced Vehicle Research Center or Luscious Garage will do the job for you. What's more, you don't have to worry about frying your car — or yourself — because many of the safety concerns have been addressed. The $9,995 kit from Hymotion, for example, has been crashed-tested and comes with a three-year warranty. The California Air Resources Board wants to take things a step further with a rule that would, among other things, require kits be warrantied for seven to 10 years.

Although the plug-ins burn less gas and emit a whole lot less CO2 — even when drawing their juice from coal-fired powerplants — than cars running on dino juice, you'll probably never save enough money to recoup the cost of the conversion. Uncle Sam so far hasn't been inclined to cut early adopters any slack. Although the Senate has approved a bill that includes some serious tax credits for plug-in hybrids built by the automakers, there's no word on whether it'll cover converted cars. But EV evangelists say money isn't the point. "If you're using payback to justify buying these systems, forget it," Protheroe says. "Ride a bicycle."

Photo by Alison Gannett.

Be sure to check out Wired.com's How-To Wiki for a rundown on converting your hybrid.