Toyota says that it has developed a "plug-in hybrid" that's certified for use on public roads in Japan. The move may put Toyota, at least for now, ahead in a race among major automakers to bring such vehicles to market--vehicles that would allow drivers to rely on electricity from the grid for short trips. For longer trips or to help with acceleration, a gas engine kicks in. And unlike with electric cars, plugging in plug-ins is optional.

In the case of the new Toyota vehicle (dubbed for now simply Plug-in HV), the electric-only trips will be very short--just eight miles on a single charge. That electric range is a fraction of the 33 miles that Americans drive on average each day. But those electric miles will still save a considerable amount of gas.

Toyota's chief competitor is General Motors (GM), which less than a year ago began touting its plan to develop two plug-in hybrid vehicles, neither of which is ready yet. (See "Powering GM's Electric Vehicles" and "GM's New Electric Vehicle.") One plug-in hybrid, a version of its Saturn Vue, would have an electric range similar to that of the Toyota car: about 10 miles. The other is an entirely new vehicle called the Volt, an electric car that would use power stored from the grid for the first 40 miles, then rely on electricity from an onboard gasoline-powered generator for another 600 miles.

Toyota may be slightly ahead at bringing a plug-in to market. But the company has done this by relying on conventional batteries--the same nickel-metal-hydride batteries it uses now in the Toyota Prius. GM is opting for advanced lithium-ion batteries, which are much lighter and smaller, and therefore can provide greater range without sacrificing cargo space. (Advanced lithium-ion batteries are not prone to explosions, unlike the lithium-ion batteries used in laptops today, which have led to massive product recalls.) But lithium-ion batteries have yet to be proved in production vehicles.

The question is whether it's better to go with established battery technology at first, then shift to better technology later, as Toyota seems to be doing, or to follow GM's approach, which is to specifically design vehicles from the beginning for a superior battery technology, even though this could delay the first vehicles.

Felix Kramer, a longtime advocate of plug-in hybrids at an organization called Cal Cars, supports the first approach. The idea is to get vehicles on the road, driven by actual customers, as soon as possible as a way to gain valuable insight for a next-generation car. In practice, this is what happened with the Toyota Prius. Most people won't recall the early version of this car, which looked like an ordinary sedan. The next iteration, with the distinct styling of today's Prius, improved as a result of lessons learned from the first iteration and performed much better. Sales of the Prius have taken off in the past few years.

But GM is betting that the new battery technology will be worth the wait. Toyota may have the first plug-in on the market, but GM may have the first plug-in that most Americans can use for commuting without using gasoline. The Volt's anticipated 40-mile plug-in range is more than Americans, on average, drive each day, allowing many to skip trips to the gas station. For most drivers (who drive farther than eight miles between charges), the Toyota vehicle will offer only fewer trips to top off with $3-a-gallon gas, a less-compelling incremental improvement.

In all of this, however, Toyota has the huge advantage of having led the way with hybrids, while GM is perhaps best known for gas-guzzling SUVs and for scrapping its electric car, the EV-1. Overall, the best news for consumers is that the automakers are competing. That keeps the pressure on to get these cars on the market.