Energy Tax Credit for Hybrids purchased or placed into service after December 31, 2005 may be eligible for a federal income tax credit of up to $3,400 according to Fuel Economy (http://www.fueleconomy.gov). Credit amounts begin to phase out for a given manufacturer once it has sold over 60,000 eligible vehicles.

Does the tax credit only available for taxpayers with curtain income bracket? Is there any income qualification?

Yes, there are limitations based on income brackets.