Power to the People: How to Run Your House on Your Car

Jim Motavalli

Jim Motavalli | Aug 11, 2011

Here’s a scenario: An electric storm knocks out power to your house just as the Super Bowl is starting. Do you knock on the neighbor’s door with a six-pack, a bag of pretzels and a contrite expression on your face, or do you try something much more innovative—plugging your television into your Nissan Leaf’s 24-kilowatt-hour battery pack.

Believe it or not, that’s not science fiction. In Japan, consistent power has been a huge problem since the earthquake and tsunami, and Nissan is one of many companies suffering through blackouts and shifting to a Saturday-to-Wednesday work week. And it’s a reason Japanese customers will now have "Leaf to Home" as an option, with two days of available electricity. Spokesman Shiro Nagai said the system will be commercialized in Japan sometime before next April, and that it is likely to be introduced to the U.S. and other foreign markets—adapted to local utility grids—shortly afterwards. Nissan North America told me it’s “working on it.”

Charging your house from your car will soon be routine for Japanese Leaf owners. (Nissan photo)
Charging your house from your car will soon be routine for Japanese Leaf owners. (Nissan photo)

This sounds like the technology of the future, but actually it’s not new—just new as an official automaker concept. A bunch of home experimenters were able to get their Toyota Priuses handling blackout duty way back in 2007. Chris Swinney, a Florida-based anesthesiologist, told me then that he’d connected his hybrid into the backup uninterruptible power supply at his house during a power outage, and soon had the refrigerator producing cold air and the lights blazing. “It was running everything in the house except the central air-conditioning,” he said.

This week, Swinney told me he's still an enthusiastic believer in plugging in to his Prius, and he applauds Nissan's action. "It's an awesome idea," he said. "Now we need 'Prius to Home' technology, because that would really be a killer app." Are you listening, Toyota? The company so far seems lukewarm to the idea. Swinney added that he'd buy a Leaf tomorrow if his work as a traveling anesthesiologist didn't take him from hospital to hospital, and sometimes well over 100 miles a day.

The Prius’ nickel-metal-hydride battery pack is only 1.3 kilowatt-hours, a fraction of the Leaf’s, but it can still be very useful in blackouts. On its own it would run out of power in an hour, but with the gas engine cycling on and off it will act like a generator, provide up to three kilowatts, and keep the lights on as long as there’s fuel in the tank—days, or even a week if you don’t plug in too much. The UPS unit’s inverter turns the DC from the batteries into AC for the house. You can read about how it’s done here.

Richard Factor is a New Jersey-based entrepreneur who’s powered his home from his hybrid cars many times. “It works just fine,” he told me. The necessary modifications to the car itself are minimal—just an output connector that can plug into the UPS unit. Factor says that his Prius is in many ways better for blackout duty than the Leaf he has on order, despite its small battery. The Leaf has plenty of power, but no generator to keep its pack charged up. Add a portable charging dock, and you could actually use your Prius to recharge your stranded Leaf.

“I like the idea—if you have a Prius, you might as well take advantage of it,” Ray Magliozzi told me. “Of course, that’s as long as it doesn’t cost too much. For $300, you can go down to Home Depot and get a back-up generator that will run all night.” You will probably save some money—really capable UPS units are $150 or so, and the rest is assorted wiring. The Prius is also a partial-zero emission vehicle, so it’s probably cleaner when it’s running than that Home Depot generator.

In the broader sense, cars can be backup power for electric utilities in a concept known as vehicle-to-grid (V2G). Imagine the collective power of an entire neighborhood of granola-eating Prius owners! Erica Gies of Forbes.com says your Prius can become a “cash-back car.” She writes that people could theoretically earn as much as $1,000 a year (netting $440 after paying for the gas) to keep your Prius (or other fine car) plugged in and available to the grid.

A scientist named Willet Kempton at the University of Delaware has been working on this since 1997. The Department of Defense, with 200,000 vehicles in the fleet, is taking it seriously. Google bought into the concept, too, and built a number of Priuses that could give power back to the grid. I saw a demonstration in Palo Alto, with an electric meter spinning backwards.

Kempton’s plan is moving forward, since he recently convinced PJM Interconnection, an electricity wholesaler that provides power to 13 states, to enable a system that paid people for giving power back to the grid. A pilot project is now underway, and the Federal Energy Regulatory Commission (FERC) has a pending rule to smooth the way for this, too.

It won’t work for solo Prius owners—at least 15 cars will have to be grouped together to aggregate as a big battery that would be worthwhile for utilities. Are there 15 Priuses (or Leafs) in your neighborhood? Soon they can be making money just plugging in, which may beat selling magazine subscriptions door to door as a source of pocket money in a sour economy.

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