Thanks to the Energy Policy Act of 2005, certain hybrid and alternative-fuel vehicles can earn credits of up to $4,000. To be eligible for the Energy Policy Act of 2005, vehicles have to fall into one of four categories: fuel cell, advance lean burn technology, hybrid or alternative fuel. Currently, the only mass-market cars that qualify are hybrids and one alternative-fuel car, the Honda Civic GX.

Some popular hybrid cars, like the Toyota Prius, may no longer be eligible for the credit, depending on when you purchased one. The act called for the credits to be phased out once manufacturers reached 60,000 sales of hybrid models. Under the policy, credits are reduced and then phased out all together, correlating with sales numbers.

"So far, Toyota and Honda are the only automakers to have reached the 60,000 mark, so credits for those manufacturers are being phased out or, in the case of Toyota, were completely gone as of Oct. 1," said Cars.com editor in chief Patrick Olsen. "It will take manufacturers like GM and Nissan, who got into the hybrid market more recently, a bit longer to reach the 60,000 threshold."

Consumers who purchased a Toyota or Lexus hybrid before March 31, 2007, are eligible to claim 50 percent of the original deduction. For example, a Prius purchased in the first three months of 2007 qualifies for a $1,575 credit instead of the original $3,150. Those who purchased between April 1, 2007, and Sept. 30, 2007, can claim 25 percent of the credit, while those who bought a Toyota or Lexus hybrid on or after Oct. 1, 2007, are ineligible for the tax credits.

If you are looking to purchase a hybrid or alternative-fuel vehicle in 2008 and want to receive a tax credit, keep in mind that no Toyota and Lexus models will be eligible for a credit. Partial credits will be available on Honda hybrids through 2008. It's possible Ford will reach the 60,000 mark some time in 2008, which will start the credit phase-out for all qualifying Ford vehicles. Full tax credits are likely to be available for all GM and Nissan vehicles purchased in 2008.

What Credits Are Offered for the 2007 Tax Year?
The experts at Cars.com have detailed credits for all qualifying 2007 models. For those who purchased any of these models in 2007, credits can be claimed on their 2007 tax return.

Tax Credits by Make, Model and Year
Chevrolet
2008 Malibu Hybrid: $1,300
2008 Tahoe Hybrid 2WD and 4WD: $2,200
2007 Silverado Hybrid: $250 (2WD) or $650 (4WD) Ford
2008 Escape Hybrid: $3,000 (2WD) or $2,200 (4WD)
2007 Escape Hybrid: $2,600 (2WD) or $1,950 (4WD) GMC
2008 Yukon Hybrid 2WD and 4WD: $2,200
2007 Sierra Hybrid: $250 (2WD) or $650 (4WD) Honda
2008 Civic Hybrid: $2,100*
2008 Civic GX: $4,000**
2007 Accord Hybrid: $1,300*
2007 Civic Hybrid: $2,100*
Lexus
2008 RX 400h 2WD and 4WD: $1,100? or $550?
2008 LS 600h L: $900? or $450?
2007 GS 450h: $775? or $387.50?
2007 RX 400h 2WD and 4WD: $1,100? or $550?
Mazda
2008 Tribute Hybrid: $3,000 (2WD) or $2,200 (4WD) Mercury
2008 Mariner Hybrid: $3,000 (2WD) or $2,200 (4WD)
2007 Mariner Hybrid 4WD: $1,950
Nissan
2008 Altima Hybrid: $2,350
2007 Altima Hybrid: $2,350
Saturn
2008 Aura Green Line: $1,300
2008 Vue Green Line: $1,550
2007 Aura Green Line: $1,300
2007 Vue Green Line: $650
Toyota
2008 Camry Hybrid: $1,300? or $650?
2008 Prius: $1,575? or $787.50?
2008 Highlander Hybrid 4WD: $1,300? or $650?
2007 Camry Hybrid: $1,300? or $650?
2007 Prius: $1,575? or $787.50?
2007 Highlander Hybrid 2WD and 4WD: $1,300? or $650?
*When purchased in 2007; credits for purchases in 2008, which can be claimed on a 2008 tax return, will be lower.
**Natural-gas powered Civic GX available in California and New York.
?If purchased from 1/1/07 to 3/31/07.
?If purchased from 4/1/07 to 9/30/07. There is no credit for models bought on or after 10/1/07.

For more information about hybrid and alternative-fuel tax credits, visit Cars.com's special section on tax credits and cars at: http://www.cars.com/go/advice/Story.jsp?section=buy&subject=tax&story=taxCredit