Maybe we’re used to them by now: Hybrids silently sliding up behind us in the grocery store parking lot or on the street in front of the pharmacy, the only identification being a slight hum or a green badge on the tailgate. Whether they’ve become commonplace or not, we shouldn’t downplay that hybrid drive systems represent a colossal leap forward in terms of environmentally conscious automotive technology — and there have been only a handful of big jumps in the last century. Like that prehistoric guppy morphing into a landlubber, the addition of electric power is auto evolution in the making. In 2000 just one hybrid was available in the U.S. The 2009 model year has 20 from which to choose. But are all of them created equal?

We decided to put them to the test and wrangled up the 10 most efficient hybrids available in the U.S. We based our list on the Environmental Protection Agency’s fuel economy stats. Incidentally, these ratings have been updated starting with model year 2008. They are now more accurate, taking in real-world factors including cold weather, faster acceleration and air conditioner use. In fact, many drivers now find they get better mileage than what’s printed on the EPA window sticker. Here’s how the hybrids ranked:

Toyota Prius

Click to enlarge picture2009 Toyota Prius (© Toyota Motor Sales, U.S.A.)

Though the Toyota Prius sacrifices performance in the pursuit of fuel-efficiency, its interior is well-built and reasonably comfortable.

Love it or loathe it, the Prius is the most fuel-efficient car you can buy in America. The poster child for the green revolution is also the most popular hybrid in the world, with more than 1 million sold. The EPA ranks the 2009 model at 48/45 mpg (city/hwy). At its heart is Toyota’s Synergy Drive, which debuted in 2003. It is the same technology found in the Toyota Camry and Highlander hybrids, and also is licensed by Nissan for their hybrids, as well as Ford, but to a lesser extent. The manufacturer’s suggested retail price for a 2009 Prius runs from $22,000 to $24,270, depending on trim level.

View Pictures:  The Top 10 Most Efficient Hybrids

Honda Civic Hybrid

Click to enlarge picture2008 Honda Civic Hybrid (© American Honda Motor Co., Inc.)

Honda's fuel-sipping Civic lineup has just been updated — albeit barely — for 2009 with a midcycle enhancement and the addition of two new sedan trim levels.

Honda’s Integrated Motor Assist pairs an i-VTEC engine with an electric motor, bumping the mpg up to 40/45 (city/hwy). With 90.9 cubic feet of passenger space and 10.4 cubic feet of storage, the Civic Hybrid is slightly less spacious than the Prius. However, the hybrid Civic’s five-star frontal crash rating beats four stars for the Prius. The Civic Hybrid’s base MSRP is $23,550; leather and a nav system will bump you up to $26,750.

Nissan Altima Hybrid

Click to enlarge picture2008 Nissan Altima Hybrid (© Rod Hatfield)

The Nissan Altima is largely unchanged for 2009, although the automaker is expanding availability of its gas-electric hybrid model.

Drivers demanding more performance should take a look at Nissan’s Altima Hybrid. With a 40-horsepower electric motor alongside its 2.5-liter 4-cylinder engine, it has the feel of a V6. But at 35/33 mpg (city/hwy), it doesn’t burn gas like one. With a $26,650 MSRP, the Altima is trying to give the hybrid Camry a run for its money, but only in the nine states where it’s available: California, New York, Massachusetts, Connecticut, Vermont, Oregon, Rhode Island, Maine and New Jersey.

EscapeTributeMariner

Click to enlarge picture2009 Ford Escape Hybrid (© Ford Motor Company)

The Ford Escape, Mazda Tribute and Mercury Mariner Hybrids are basically all the same under the sheet-metal facade. Talk about two too many.

Although Ford claims its Escape Hybrid is “the most fuel-efficient SUV on the planet,” it is actually in a three-way tie with two other compact SUVs: the Mazda Tribute Hybrid and Mercury Mariner Hybrid. We’ll cover the triplets together, since they bear the same vital stats. The 2009 models of these three compact SUVs test at 34/31 mpg (city/hwy) in their front-wheel-drive models. However, all three compact hybrid SUVs drop to 29/27 mpg when adding four-wheel drive. All three carry the same 2.4-liter 4-cylinder engine that is paired with an electric motor and nickel-metal hydride battery pack. While these compact SUVs offer only a bit more passenger space than a Prius, there is much more cargo space to be found behind the rear seats.

If the goals of hybrids are efficiency and environmental responsibility, should all hybrids be created equal? Why or why not?

Toyota Camry Hybrid

Click to enlarge picture2008 Toyota Camry Hybrid

Unchanged for 2009, the Toyota Camry is soft on sport and excitement, but offers good to great levels of comfort, convenience and options.

One of the most popular cars on the road — somewhat sexier after its 2007 redesign — the Camry Hybrid is also one of the most sought-after hybrids. A 105-kilowatt electric motor and 4-cylinder engine give this car considerably more punch in the pants than the Prius, and fuel economy of 33/34 mpg (city/hwy). The Camry also offers more cubic footage for passengers than its Prius sibling. A 2009 Camry Hybrid carries a base MSRP of $26,150.