Hybrid vehicles reduce America's dependence on foreign oil and minimize emissions from greenhouse gases. But it's still a question whether they save money in the long run. The answer: maybe.

Some models achieving well over 40 miles per gallon cost thousands more than equivalent gas models, which get 30 miles per gallon. Even with gas prices at $4 a gallon, it could take driving 15,000 miles per year for 12 years to make up the difference, according to U.S. News & World Report.

That's not all. According to data compiled by InsWeb.com, the auto insurance comparison shopping Web site, it costs slightly more to insure the hybrid for a 30-year-old single male driver with a clean driving record as opposed to the gas-only model.

Another thing to consider: A report by the Automotive Lease Guide found that, after three years, certain gas models hold 60 percent of sticker value, about 2 percent more than the same model hybrid.

On the other hand, a Ford Escape Hybrid runs about $3,000 more than the conventional model, but at 32 miles per gallon will make up the price difference in less than five years and is projected to maintain more residual value than the gas-only model.

So are hybrids worth it or aren't they? It depends on which model you choose, how many years you plan to own it, fuel prices and average mileage per year.

For example, for a commuter logging 40,000 miles a year, a hybrid's increased fuel efficiency may well make it worthwhile. A retiree who drives to the grocery store once a week, however, should probably stick with a gas-only vehicle. For someone who trades in his or her car every year, gas models make more sense. For someone who plans to drive the car long into the future, it might be worthwhile to go green.

The fact is, hybrids cost more and the fuel savings only make sense if you can afford that up-front cost. You will certainly save on gas later on. If you cannot afford the outlay, then you will have to settle now for the gas-only model.