Hybrid cars have been getting a lot of buzz the last three or four years, and now with the soaring cost of oil and gasoline, hybrids are expected to get hotter than ever. Here are some Questions and Answers about hybrids.

1. What is a hybrid car?

A vehicle is a hybrid when it combines two or more sources of power. Hybrid cars almost always have a gasoline engine and an auxiliary electric motor system that runs off rechargeable batteries.

We normally assume that the point of hybridization is to save fuel, and that is definitely the case with most of the smaller compacts and sedans. But in fact some of the more upscale hybrid models are more concerned with boosting power and "performance" without the usual loss in fuel efficiency.

2. Do you have to plug your hybrid in at night?

You may assume because a hybrid car runs part of the time off its battery pack, that it is necessary to plug it in at night and recharge the batteries (like a golf cart!). But this is almost never the case. Hybrid cars recharge their batteries "on the fly" by making use of unused energy which is normally wasted during normal driving.

For instance, most have a system that captures some of the energy used while applying the brakes, and converts it to electrical energy to charge the battery. This is called "regenerative braking".

If hybrids had larger battery packs that you could plug into the electricity grid, they would be able to transfer more of the vehicle's power requirements over to the electric motor(s), and use even less gasoline. But most auto makers have been unwilling to go this route, arguing that today's batteries could not take the extra load and more extensive usage.

3. Do you have to replace the batteries?

The short answer is No. Hybrid batteries typically have an 80,000 - 100,000 mile warranty. The U.S. Department of Energy tested them to 160,000 miles and stopped testing because they still performed almost like they were brand new. Some taxi drivers have gone more than 200,000 miles in a Toyota Prius without battery problems.

In any event, since hybrid battery packs have hundreds of cells, individual cells or modules could be replaced if there was a problem.

The best way to keep nickel metal hydride batteries performing at their peak is to keep their charge between 40% and 60% -- never fully charged and never fully drained to zero power.

4. How long have hybrids been around?

Alternatives to the ICE (internal combustion engine) in automobiles have been around since at least 1900. The first patent for a gasoline-electric hybrid vehicle was filed in 1905. Alternative fuel sources were wiped out as a result of two things. First was the development of the electric self-starter (in 1913) that made gasoline driven cars much easier to start.

The second development was the advent of the age of cheap oil that started around the time of the first World War. This completely removed the economic incentive to look for alternative fuel sources. This is only starting to change now, 80 years later.

5. Are hybrids expensive to purchase?

In January, 2006, there were 10 different hybrid models available from $19,000 to $53,000. The most popular models -- the Insight, Civic, and Prius -- are less than $30,000. According to auto maker announcements there should be more than 50 models available by 2010. As sales and production increase the prices should not be significantly more than for standard ICE models.

Even with the slightly higher average cost for a hybrid -- usually around $3,000 -- these additional initial costs can be offset by federal and state tax incentives, lower maintenance costs, and exceptionally strong resale values.

6. Are hybrids small and underpowered?

Initial hybrid models emphasized