Porsche has announced that it will make a production version of its 918 Spyder plug-in hybrid concept car.

The car, which was first shown off this year at the Geneva Auto Show, can accelerate to 60 miles per hour in under 3.2 seconds, and reach a top speed of 198 miles per hour. It pairs an electric motor with an eight-cylinder engine. Drivers will be able to putter along for 16 miles using electricity alone. In ordinary hybrid mode, the car can get 94 miles per imperial gallon (about 78 mpg). For the highest performance, select Sport Hybrid or Race Hybrid mode. The latter includes a "push-to-pass" button that delivers a surge of power from the battery.

With Porsche getting in on the electric-powered action, one wonders how up-starts like Fisker and Tesla will manage.

GM has announced that it will sell the much-anticipated Chevrolet Volt--an electric car with a gas generator for extending driving range--for $41,000, which is about what people had been expecting. The automaker notes that with a federal tax credit, the actual cost to consumers is $33,500.

GM starts taking orders for the car today. It will be available initially in California, New York, Michigan, Connecticut, Texas, New Jersey and the Washington D.C. area. To buy one, you need to go to a Volt dealer, which you can find at http://www.getmyvolt.com.

The car costs more than the Nissan Leaf, which is also coming out this year. That car will sell for $32,780, or $25,280 after the tax rebate. Both are far more expensive than GMs new, more fuel efficient sedan called the Cruze, which costs $16,995 and is similar in size to the Volt.

With the Cruze, you can get 40 miles per gallon (with the Eco version). The Volt offers 40 miles of electric range with a charge, and 300-miles more with a range-extending gas generator. The Leaf offers 100 miles of gas-free driving range between charges.

Last week Nissan showed off the battery and drivetrain platform for its upcoming electric vehicle. Now it's revealed the car itself--the Leaf.

This zero-emissions vehicle, which has a range of 100 miles on a charge, will go on sale next year in Japan, the United States, and Europe. It will be powered by a lithium manganese battery developed in a joint venture between Nissan and NEC. Manganese-based lithium ion batteries are popular with automakers (GM plans to use one in the Volt) because they're more stable than the cobalt oxide batteries commonly used in laptops and other portable electronics.

Nissan is taking a markedly different strategy than companies such as Toyota, GM, and Chrysler, which have emphasized hybrid vehicles that can run on both electricity and gasoline. Even the Volt, which GM is describing as an electric vehicle, has an onboard gasoline generator that kicks in after 40 miles of driving to recharge its battery. Because gasoline stores orders of magnitude more energy than batteries, such vehicles can have longer range than pure battery electric vehicles like Nissan's Leaf. What's more, fuel tanks can be refilled much faster than batteries can be recharged, at least without special electrical connections, making long-distance road trips easier. (Electric vehicle enthusiasts like to brag about cross-country trips, but these require careful planning--it's good to find RV parks equipped with 220-volt outlets--and a willingness to take frequent breaks while the car charges.)

Nissan has been working with a company called Better Place on a strategy for extending the range of EVs. The idea is to build battery swap stations along major highways. Drive in and a simple robot takes out your car's depleted battery and inserts a charged one, and you're quickly on your way again. Nissan demonstrated one version of a swap station in May.

But it wasn't immediately clear whether the Leaf would be compatible with swap stations. A spokesperson for Nissan said that the company doesn't plan to use a swap strategy in the United States, but she expects the Leaf could be used with swap stations in other countries. She said she'd get back to me to confirm. (If she does, I'll add that here.)

Many EV supporters say it doesn't make sense to buy a car with a gasoline engine and fuel tank as well as an electric motor and battery pack. After all, most of the time either one or the other is just dead weight, sitting there unused. They say, if you commute less than 80 miles each day, buy an EV. Then, for those relatively rare occasions when a longer range is required, rent a car. Or use the EV as a second vehicle.

But one of the most expensive parts of an EV is the battery, and most people actually commute less than 40 miles a day. If you can make do with a battery pack half the size, you could save money, even with the added cost of a gasoline generator. So either strategy--pure EV or hybrid--could make sense.