The return of cheap gas has been the one light moment in this tear-jerking economy. However, relief at the pump has been crushing for sales of hybrid cars, which have tanked faster than even the auto market at large.

When gas prices ballooned to over $4 a gallon last year, gas-electric cars were widely viewed as the clear successors to today's gas-only dinosaurs. Flush buyers happily shelled out thousands of extra dollars for these environmentally conscious autos, because hybrids were better for the environment and would deliver better fuel economy. But now that the average cost of a gallon of regular in the U.S. is only $2.05 (AAA, March 30, 2009) and recession-riddled consumers are watching every penny, hybrids seem to cost too much and do too little in return. As a result, struggling automakers — which start designing new models several years before they go on sale — are begging the government for an energy policy that helps them anticipate what consumers will be buying.

The travails of show the conundrum for automakers. Last July, when gas prices peaked at $4.11 a gallon, Toyota couldn't crank out enough Priuses to meet demand. The company immediately idled a newly christened plant in Texas, which was dedicated to full-size, gas-guzzling pickups and SUVs, and hastily redesigned the plant it had just broken ground for in Mississippi, shifting production from the Highlander SUV to the coveted .

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Eight months later, with gas prices cut in half, Prius sales are tanking, along with those of most other hybrids. The Mississippi plant is completed, yet there's no firm date to begin building the redesigned 2010 Prius there, which goes on sale this spring. A factory in Japan will continue to make the Prius for U.S. customers.

"The project is on hold until hybrid markets recover," Toyota spokesman Wade Hoyt says. "It shows how hard it is to plan years ahead as you design new models or even assembly plants. We'd like some stability in both fuel prices and consumer confidence so we know where we're going."

Some automakers saw an upside in hybrid SUVs, figuring that consumers wanted better mileage from the big trucks they'd come to love. General Motors and Chrysler bet on these hulking hybrids and failed spectacularly: Priced roughly $6,000 above their gasoline versions, the hybrid , GMC Yukon and have found few takers. Chrysler's own hybrid Dodge Durango and SUVs, using the same 2-mode hybrid system developed with GM, BMW and Mercedes-Benz, were canceled just weeks after they went on sale.

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Those failures may not bode well for upcoming Mercedes and BMW SUVs that employ the same hybrid system. The long lag between the drawing board and showroom means that automakers have no choice but to move forward with existing hybrid plans.

Undeterred, will send a redesigned Insight to showrooms in April. Honda believes the Insight, as the nation's lowest-priced hybrid, will hold mass appeal. Starting at just $20,470, the Insight is rated at 40 mpg city/43 mpg highway. It will battle the new Prius, which Toyota estimates will achieve roughly 50 mpg in both city and highway driving. The , whose 41 highway mpg makes it the nation's most economical midsize sedan, is already on sale. Later this summer, Lexus will offer the roughly 33-mpg HS 250h sedan, the first Lexus available only in hybrid form. GM will try again with a Saturn Vue 2-mode hybrid that delivers 32 mpg on the highway.