Factor in the price of gas — currently sloshing around at $3 a gallon — and there may be no better time to give that Toyota Prius or Saturn VUE a try.

More cars, increasing demand
Enterprise currently operates the nation’s largest fleet of hybrid cars, with approximately 5,000 vehicles. Four models are available nationwide, but they’re not broken out individually on the company Web site, making reserving one a bit of a challenge.

At Hertz, hybrids are offered at the company’s top 50 airport locations and can be reserved as part of the company’s Green Collection, which lets customers book, not just a class or size of car, but a specific make and model. With the new arrivals, the company’s hybrid fleet will total 3,400 vehicles.

Avis, meanwhile, offers 2,500 hybrids in three classes. They’re available primarily at major airports in California and cities including Portland, Ore., Seattle, Chicago, New York, Washington and Boston. Fox Rent A Car, a Los Angeles-based discount operation, offers hybrids in Phoenix and seven locations in California.

Given the chance, most companies would like to offer even more hybrids. “There’s such high demand at retail,” says Pat Farrell, Enterprise’s vice president of corporate responsibility. “We’d go for 10 times the number we have if we could get them.”

For consumers, of course, the big draw is the breed’s impressive environmental credentials. According to Toyota, the Prius emits 70 percent fewer smog-producing emissions than the average new car. It’s also a genuine gas-sipper, earning a combined city/highway EPA rating of 46 miles per gallon.

At $3 per gallon, the savings can be significant. “If you drive 500 miles and get 50 miles per gallon, it will cost you $30 in gas,” notes Hertz spokesperson Paula Rivera. “In an ordinary car that gets 20 miles per gallon, you’ll spend $75.” The farther you go, the greater the savings.

Conversely, you’re less likely to come out ahead — at least financially — on shorter trips. “If economics are more important and you won’t be putting a ton of miles on the car,” says Avis spokesperson John Barrows, “you might be better off with a [traditional] compact car that has high fuel efficiency and a lower day rate.”

Pay a premium (or not), protect the environment
So what should you know about renting a hybrid?

Most important, recognize that you’ll usually (though not always) pay a higher day rate for a hybrid compared to a like-sized non-hybrid. For example, a recent search for cars in New York and Los Angeles revealed that the added cost to “go green” ranged from zero to $24 per day. Company, location, length of rental — it all comes down to who has cars available.

Note, too, that policies vary by company. At Avis, Fox and Hertz, you can specifically reserve a hybrid online or by phone; at Enterprise, you can only reserve a class or size of car. To get a hybrid, the company suggests expressing your interest when reserving and following up by phone with the destination branch to explore the options.

Still, even if you don’t get a hybrid at Enterprise, you can help the environment. This week, the company will launch an industry-leading program that will let renters at its three company brands (Enterprise, Alamo and National) offset the greenhouse gases produced by their rentals.

During the reservation process, renters are given the option of paying $1.25 per rental to offset their emissions. (The figure is pegged to the CO2 produced during the average car rental.) Funds collected are passed on to TerraPass, a carbon-offset company that supports projects that work to remove CO2 from the atmosphere.

The program is part of a much larger environmental initiative that ranges from funding renewable-fuel research to helping plant 50 million trees over the next 50 years. In total, the company’s efforts on behalf of the environment are in the neighborhood of $100 million.

Still, says Farrell, the carbon-offset program is new ground, and there’s no way to know how customers will respond — one reason the company will match contributions up to $1 million. “We don’t know how it will play out,” he says. “I’m hopeful that we’ll spend the million.”