The Prius You Can Plug In

What’s a Plug-In?

This modified Toyota hybrid, developed by Energy CS of Monrovia, Calif., operates just like any other Prius, but it can get more than 100 mpg on long trips because the 1.3-kilowatt hour (kWh) battery has been replaced with a more powerful 9-kWh Valence Technologies lithium-ion battery pack that can be recharged from a standard electrical outlet. At residential neighborhood speeds (less than 35 mph), specialized monitoring and control circuits in the Energy CS Prius automatically select electric operation — resulting in almost zero tailpipe emissions — during the first 50 to 60 miles, minimally “boosted” by the gas engine until the battery charge is depleted. After that, the Energy CS plug-in falls back to the mileage of a standard Prius.

As a result, the Energy CS Prius would stay almost exclusively in electric mode for short, local trips and use only a small fraction of the gasoline consumed by conventional cars. In low-speed city driving and 55-mph highway driving, it’s possible to average more than 200 mpg. Faster 65-mph driving, however, will result in 100 mpg or less, and 75-mph highway driving will average less than 80 mpg. For longer, mixed-driving trips up to 70 miles, the modified Prius averages between 120 and 180 mpg, depending on driving habits, hills and car speed. Because electric motors are much more efficient than gas engines, the air pollution from a plug-in is much less than that produced by an internal-combustion, gas-powered vehicle (for more information, see The Potential of Plug-ins, which is available in the October/November issue).

“They’re basically like some current hybrids, but with larger batteries and the ability to recharge conveniently so local travel is electric, yet the vehicle has unlimited range when it switches to the gas engine,” says Felix Kramer, founder of The California Cars Initiative (CalCars). “While currently available hybrids may cut gasoline use by one-third, plug-in hybrid-electric vehicles can cut out another third.”

A Hesitant Auto Industry

So why don’t all hybrids get this kind of mileage? The whole industry — not just Toyota — took great lengths to distance itself from the plug-in idea because automakers felt Americans wouldn’t cozy up to the idea of plugging in their vehicles each night, and because the cost of the higher-voltage batteries is currently prohibitive. The lithium-ion batteries found in the Energy CS Prius at the Tour de Sol, for instance, cost $15,000 alone, and they weigh 160 to 190 pounds more than the standard Prius battery pack.

“We think the plug-in concept is interesting, and Toyota will be doing its own research into it,” says Cindy Knight, a spokesperson for Toyota. “But we see a big distance between tinkering with a prototype and bringing one to market. When better breakthroughs in technology become available, we’ll be interested.” In fact, a number of environmental organizations, such as the American Council for an Energy Efficient Economy, are researching the long-term viability of plug-in hybrids.

The Plug-In Revolution

While major automakers claim current plug-in hybrids are too costly to successfully market, CalCars is busy trying to narrow the cost gap through incentives, subsidies and rebates from public and private sources. Kramer says eager plug-in hybrid buyers are the key piece of the puzzle to reach mass production. On the commercial side, Energy CS’s newly formed company, EDrive, has successfully demonstrated the effectiveness of the technology — proven by the company’s finish in the Tour de Sol. In 2006, EDrive intends to sell its plug-in conversion services to Prius owners for about $12,000. While the price of such a conversion is steep, the goal not only is to revolutionize the market, but also to convince large automakers such a market exists. Once EDrive can show interest and investment in its own plug-in conversion kit, related products will enter the market at increasingly competitive prices.

“Our goal is to persuade Toyota and other automakers to build plug-in hybrids for a market we expect to expand as state and international greenhouse gas initiatives are phased in,” Kramer says. “We’re exploring with public officials ways to provide incentives to automakers to build them. We’re demonstrating demand initially from early-adopter individuals and institutions.” One organization helping to promote the plug-in hybrid concept is the South Coast Air Quality Management District, which gave Energy CS $130,000 to convert four Prius’ to plug-ins that will be tested in several car fleets.

Making Plug-Ins Affordable

The high cost of plug-ins is directly related to their increased number of batteries, and the availability of affordable advanced battery technology will be a crucial challenge to the growth of the plug-in market. But battery technology is improving rapidly, and when combined with larger scales of production and more dollars for research and development, the upfront cost of lithium-ion batteries could be reduced.

Assuming EDrive and other proponents such as CalCars can prove there’s a viable market and cost-effective blueprint for selling a plug-in hybrid, it could become an option on any hybrid car. People currently pay extra for such luxuries as automatic transmission, leather seats and more powerful engines, so it shouldn’t be hard to convince car buyers to pay more for the plug-in option.

The big question is just how much money will the general public pay for this option? A 2004 study by J.D. Power & Associates suggests the answer is directly affected by the price of gas. As the cost of gas rises, so does the demand for more efficient automobiles. Experts think that a mass-produced plug-in hybrid could be built for as little as $3,000 more than that of a regular hybrid model. If this is true, fuel savings could offset the upfront cost of a plug-in hybrid quickly — especially if incentives and subsidies are available.