DETROIT - Over the next few years automakers will be rolling out a variety of electrified vehicles to help them meet sharply higher government fuel economy requirements. But absent higher gas prices or larger consumer incentives, the new technologies are still too costly to justify. What's worse, you're often paying for more than just better fuel economy.

All things being equal, a hybrid power train adds about $3,000 to the cost of a car in exchange for a 25 per cent improvement in fuel economy. At current prices of fuel, would take about eight years to break even on the purchase, says research firm CSM Worldwide.

But hybrid versions of vehicles typically carry an even higher premium. Why? A new study by the Union of Concerned Scientists found that too often the price includes thousands of dollars' worth of luxury features you might not otherwise have chosen, like DVD players, keyless entry systems and leather interiors.

You'll save gas, but it'll take even longer to break even on your hybrid purchase because of the inflated sticker price. 

"Hybrids don't have to be luxury vehicles," said Don Anair, an analyst with the Union of Concerned Scientists who ranked green vehicles according to their environmental bang for the buck. "Car buyers shouldn't be forced to buy high-end bells and whistles when fuel economy and reducing emissions are their top priority."

The Toyota Prius, whose hybrid power train costs an estimated US$3,000, scores highest for its environmental benefits and hybrid value. But even the lowest-priced Prius comes with US$1,600 worth of extra features not found on the entry-level Toyota Matrix, which is comparable in size and performance.

The study found that consumers often don't have the option of simply adding a hybrid system to a base model; instead, many hybrid models come with premium or upgraded features as standard equipment. These "forced features" inflate the cost of the hybrid, putting it out of reach for many consumers.

The 2009 Honda Civic hybrid is a good example.

This car gets high marks for its environmental performance. But you can get the hybrid Civic only as a fully loaded model, with features like cruise control, security system with remote entry, rear spoiler and vehicle stability assist with traction control. All that stuff adds US$3,362 to the price, on top of the US$4,000 hybrid power train. You'll end up paying US$23,550 for a hybrid version of a car that starts around US$16,000.

At $3 per gallon of gas it'll take more than 15 years to break even on the purchase. It would take 8 years if you weren't paying for all the added features.

The 2009 Ford Escape hybrid has the same problem. At US$31,395 it costs US$8,000 more than the conventional all-wheel-drive Escape crossover. It reduces CO2 emissions by 25 per cent and gets 28 mpg. But the hybrid system costs $5,795 -- pricey compared with the one in Ford's 41 mpg Fusion hybrid, which costs an estimated $4,190. And you have to pay $2,205 for features on the Escape hybrid you might not want, like satellite radio, Ford's SYNC communications and entertainment system; fog lamps; leather-wrapped steering wheel with audio and cruise controls and power adjustable seats.

It, too, would take 15 years to break even on the purchase (or about 11 years without all the extra equipment).

Even worse is the 2009 Chevy Tahoe Hybrid. General Motors had the right idea by trying to give consumers their big SUV and better fuel economy, too. But the hybrid version of this four-wheel-drive truck doesn't make much of an environmental impact. It reduces CO2 emissions by about 20 per cent, but the EPA gives it a low score on tailpipe emissions. And it costs US$53,260, compared with US$41,025 for the gasoline version.

That huge price gap is only partially explained by the cost of the hybrid power train (US$5,275). The remaining $6,960 is for all the features that come standard on the hybrid model: a bigger gasoline engine, heavy-duty rear-locking differential; rear parking assist; a Bose audio system with DVD-based navigation and nine speakers; rearview camera system; universal home remote; and remote vehicle starter.

The payback time for the hybrid Tahoe would be a little over nine years if you weren't paying for all those bells and whistles. But you can't get it without them, extending the payback time to 22 years.

The luxury Lexus LS 600h L hybrid is the worst offender, according to the Union of Concerned Scientists study. At $106,035 it costs $38,685 more than the base model LS 460L. That includes more than $17,000 in forced features beyond the normal luxury amenities found in a Lexus.

What about its environmental benefit? Forget it. This is a muscle hybrid: At 438 hp it's about boosting performance, not saving the planet. You're not likely to live long enough to break even on the purchase. At the current price of fuel, it would take 108 years to break even (only 48 years if you didn't have to pay for so many extra features).

CSM figures the technology behind a range-extended plug-in hybrid like the Fisker Karma or the upcoming Chevrolet Volt costs US$10,000. You'll get 40 miles or so on electricity, and 50 miles per gallon when you're using the backup gasoline engine for longer distances. But it'll take 6.4 years to break even on the technology, says CSM.

A pure electric vehicle will take even longer. CSM estimates the technology costs US$20,000 (mostly for an advanced lithium-ion battery capable of 100-mile range). You'll pay only 34 cents a mile, the payback period is 14.7 years.

None of these analyses accounts for federal tax credits ranging from US$2,500 to $7,500, depending on the car's battery capacity, for the first 200,000 vehicles sold. Many states also offer incentives. (California, for instance, offers up to a US$5,000 rebate on top of the $7,500 federal tax credit for the purchase of a pure electric vehicle.)

Anair says the big lesson for car buyers trying to go green is to run the numbers before opening their wallets. "The good news for consumers is there are a lot of great hybrids out there," Anair said. "But you can't trust the hybrid label alone. You need to look at how much environmental performance you're getting for your money."