Toyota Prius hybrid owners convert their cars to plug-ins

• Six Prius dealerships in the US convert standard Priuses • Lithium-ion battery is installed in space for spare tire

Suzanne Goldenberg
guardian.co.uk, Thursday 16 April 2009 12.30 BST

The major US automakers are not due to roll out their first electric cars until late 2010, but for those unwilling to wait, there is a new trend for DIY plug-in hybrids.
Owners of the popular Toyota Prius hybrid, which runs on petrol and a nickel-metal battery, have begun a slow-but-steady move towards converting their cars into plug-in vehicles. A few hundred Prius owners around America are believed to have taken the plunge.
Six Prius dealerships in the US now convert standard Priuses into plug-ins using commercially produced lithium-ion batteries.
The process is straightforward. The mechanics install a lithium-ion battery in the spot formerly reserved for the spare tire. They then drill a hole in the rear of the car to put in a plug point for charging. The battery has a range of 35 to 40 miles, and takes about five hours to recharge completely.
Prius owners have long had a reputation for trying to eke the maximum miles out of every drop of petrol – trading tips on the web. But the conversions began gaining a following in mid-2008 when prices at the pump rose above $4 (£2.68) a gallon.
With that in mind – along with moves into plug-ins from Chevrolet and Chyrsler as well as tax incentives from the Obama administration for hybrid vehicle owners – Toyota moved up the date for its roll-out of the first 500 purpose-built plug-in Priuses to later this year.
The cost of the conversions is prohibitive. Steve Rosenstock spent $10,900 converting his red 2008 model Prius to a plug-in – roughly half the cost of the entire car.
Rosenstock showed off his newly converted Prius at a renewable energy conference in Washington this week. On the open road, at constant speeds and in flat conditions, he has achieved mileage of well over 100mpg. That's a considerable increase in efficiency over the standard Prius model which gets around 60mpg on the motorway.
In terms of running costs, if the petrol engine never comes on, Rosenstock says it costs about 1.57 cents to run his Prius. If the engine does engage, it comes to 4 cents a mile.
Rosenstock, who works at the Edison Electric Institute, a lobbying group for the US electricity industry, does not use the car to go to work and so does not charge it up regularly. He said there was no real increase in his electricity bills. Even so, he admitted he is unlikely to ever recover his investment.
"The first plasma TV cost $10,000. The first DVD player cost $1,000," he said. "I like being an early adopter in this case."