The Specs on Toyota's Plug-in Prius

(page 2 of 2)

Among the main differences, the plug-in Prius has twice the battery power of a conventional hybrid Prius, which adds 100kg to its weight. That also means that there's no space for a spare tire. Instead, the test models come with a puncture repair kit.

There are some key design differences between the plug-in Prius and GM's Volt. For instance, the Prius plug-in, like a conventional Prius, is powered by either its gasoline engine or its electric motor. The Volt, by contrast, is essentially an electric vehicle, powered by an electric motor, which uses an auxiliary engine and a generator to recharge its batteries.

Green Benefits Vary

Toyota reckons its system is more cost-effective and will require less space for batteries. "We concluded that Toyota would build a plug-in using the Toyota hybrid system, which has been in use since 1997, as a base," says Takimoto.

In terms of environmental performance, Toyota's plug-in Prius is cleaner than current hybrids on the market. Even with heavy nickel metal hydride batteries, the environmental benefits are impressive. In Japan, Toyota calculates that the reduction of carbon dioxide emissions, including emissions created in the production of the electricity used to recharge the batteries, will be 13% better than for a normal Prius, assuming it's driven 25km a day. That's on top of the 40%-50% less carbon dioxide a conventional Prius emits compared with an equivalent gasoline model.

However, the level of emissions reduction varies from country to country, depending on how the electricity is produced. In France, which relies heavily on nuclear power, the projected carbon dioxide reduction could be as much 45%, Toyota estimates. But in the U.S., where most energy is created by burning fossil fuels, the benefits are far smaller, at an estimated 4%. Toyota says those benefits could be boosted by the use of biofuels, which the plug-in Prius accepts.

Current Range: 13km

Operating costs are also lower. Toyota estimates that, in Japan, the plug-in Prius will cost 8% less to run if recharging is conducted during the daytime. If recharging is carried out at night, when electricity is cheaper, that savings could rise to 41%.

And what about performance? In electric mode, the maximum speed of the plug-in Prius is 100 kilometers per hour, after which the 1.5-liter gasoline engine kicks in. That's an improvement over the current Prius, where the maximum speed before the gasoline engine kicks in is 68kmh. Recharging takes 1-1.5 hours at 200 volts or 3-4 hours at 100 volts.

Still, it's the cruising range—at just 13km—in electric mode that shows just how much Toyota needs lithium-ion cells. Even in Japan, where 70% of people drive less than 30km per day, that's not a great distance. "The cruising range of 13km is purely a provisional figure," says Takimoto. "The testing will clarify the necessary requirements for the batteries." For Toyota, like GM, developing those batteries remains the key requirement for its plug-in plans.

Rowley is a correspondent in BusinessWeek's Tokyo bureau.