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Robb Protheroe, chief executive and founder of Petaluma, Calif.-based Plug-In Supply, isn’t sure if the business he’s in will be around for much longer.

Plug-In Supply’s proposition is simple. For about $5,000, plus installation costs, it’ll juice up your Toyota Prius with old-fashioned lead-acid batteries that will give you a gasoline-free commuting range of about 10 miles.

For $11,000, you can get lithium-ion batteries that can deliver an all-electric range of up to 20 miles, Protheroe said. Both kits can increase fuel economy up to 100 miles per gallon, he said.

But the plug-in hybrid conversion-kit manufacturer faces the same challenges as many of its peers.

First of all, the kit doesn’t save drivers enough gas money to pay back the cost in less than 10 years.

And don’t Toyota Motor Corp. and General Motors Corp. intend to come out with their own plug-in hybrids by the end of the decade, hitting the market with what are likely to be cheaper alternatives to conversions?

Protheroe said he hopes they’ll do it as quickly as they can.

That’s because his future is in converting purely gasoline-powered vehicles to hybrid-electric power, supplying electric-vehicle parts and systems to manufacturers, and just generally "making cars better.”


"I’m not a car company, and I’m not going to compete with a car company," he said. "I'm selling this system in order to bring pressure on the car companies to do this."

But the pressure from companies like Plug-In Supply has brought some results.

Phil Gott, director of automotive consulting at Global Insight, estimates that about 2.8 million hybrids will be on the road by 2013, 1.5 million of them in the United States.

That’s not a bad leap from the approximately 150 plug-in hybrids on the road today, according to plug-in hybrid advocacy site

Big guys also are getting in on the act. Toyota has promised plug-in Prius models for commercial fleets by 2009, although it has set no firm date for the consumer market, and General Motors expects to bring its Chevrolet Volt to the market in 2010.

So plug-in hybrid converters – Hymotion, Hybrids Plus, EDrive Systems and a handful of others – can take a certain satisfaction in the idea that they’ve helped jump-start a movement.

But as an 18-year veteran of the electric-vehicle business, who built aircraft tugs for the U.S. Air Force and hybrid buses for the Denver Regional Transportation District, he knows that his business is, well, converting itself.

"It became pretty obvious pretty quickly that we had to do battery systems in general," Lawrence said. "We know there’s a limited window of opportunity for the conversions. We’ve already planned past that point."

Those plans include building prototypes for manufacturers of specialty vehicles like parking patrol cars, as well as the new field of vehicle-to-grid technologies that could let utilities draw on the batteries of electric or hybrid vehicles when they're plugged in for recharge in order to meet peak power demands.

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