Most Fuel-Efficient Hybrids

As Hybrids become more prevalent, Toyota and Honda continue to dominate the lot, with four of the industry's five most fuel-efficient models between them.

In Pictures: Most Fuel-Efficient Hybrids

Honda's Insight and Civic Hybrid, and Toyota's Prius and Camry Hybrid offer drivers 52, 42, 46 and 34 miles per gallon, respectively. Nissan's Altima Hybrid (34 miles per gallon), boasting hybrid technology licensed from Toyota, rounds out the group.

How Hybrids Work

Electric motors, regenerative braking and automatic engine shutoff contribute to these cars' impressive fuel economy.

A battery-powered electric motor allows for the car to run on a smaller and more efficient gasoline engine. At high speeds and while accelerating, the electric motor supplements the conventional engine's power, and at low speeds — when combustion engines are least efficient — the electric motor can power the vehicle. Not all hybrids are capable of running soley on electric power, though.

Regenerative braking converts the brakes' kinetic energy into electric energy, storing it in the battery to power the electric engine when needed.

When the vehicle is stopped, the engine shuts down automatically, and allows for a quick restart. In a conventional vehicle, depending on engine size, idling uses between one-tenth and one-third of a gallon of gasoline per half hour.

These tenets of hybrid technology have remained largely unchanged since Honda introduced the Insight Hybrid to the U.S. market in 1999. The company discontinued the Insight in late 2006 to make room for a new hybrid in 2009. But Honda continues to lead the industry in overall fuel economy — its cars and light trucks boast an average of 29 mpg, thanks partly to the four-cylinder, 110-horsepower Civic Hybrid, third on our list.

Impressive, yes. But the Toyota Prius can top that. Its distinct design and unmatched fuel economy have helped Toyota sell nearly half a million Priuses in the U.S. — more than any other hybrid model.

With the exception of the Insight, the Prius' 46 mpg fuel economy beats every other mass-market hybrid sedan by at least 10 percent. Toyota spokesman Bill Kwong says, "The Prius is like the icon for hybrids. For most people, there is no second choice."

But that hasn't stopped other carmakers from trying to dethrone it. Even Nissan CEO Carlos Ghosn, who said less than three years ago that hybrids were no more than a "niche" market with "anecdotal" demand, is introducing a hybrid verion of the Altima this year — it's stocked with a Nissan engine, but uses a Toyota transaxle, inverter, battery and control unit. The Altima Hybrid pairs a 158-hp, four-cylinder engine with a 40-hp electric motor to get 34 mpg.

Ford, which introduced the first hybrid SUV, the Escape Hybrid, in 2004, has continued to bolster its hybrid fleet with the Mercury Mariner Hybrid, and will roll out an even more efficient Escape in 2008. And in addition to making hybrid trucks, SUVs and sedans, GM boasts more vehicles that get over 30 mpg than any other manufacturer.

Still, despite America's best efforts, Japan leads the pack in overall sales. Toyota's U.S. sales jumped 12.9 percent in 2006, while Honda's sales rose 3.5 percent. U.S. automakers Ford and GM saw sales drop 8 percent and 8.7 percent, respectively.

For automakers, energy efficient technology is "crucially important," says Noriyuki Matsushima, an analyst from Nikko Citigroup. "If you lose, you'll get kicked out of the market."

In Pictures: Most Fuel-Efficient Hybrids