There have been no tax credits announced for 2012. See below for rules on past 2011 tax credits.

Extended HVAC Tax Credits for 2011
What if you could make home improvements that increase your comfort, lower your energy costs, add value to your home, and do something good for the environment? And what if you could get some money back from Uncle Sam at the same time?

Updated Tax Incentives for Homeowners
Part of the tax extender bill passed by Congress in December 2010 made significant changes to tax incentives for federal taxpayers who install qualified energy efficient retrofits in their home, including higher efficiency heating, ventilation, and air conditioning (HVAC) equipment in their primary residences. An eligible taxpayer may claim up to $500 in tax credits, subject to caps based on the type of equipment installed.

You may now qualify for tax credits equal to 10% of the costs (up to a $300 limit) for installing a high efficiency central air conditioner, heat pump, or hot water heater. You may also qualify for tax credits equal to 10% of the costs (up to $150 limit) for installing a qualified furnace or hot water boiler. A smaller tax credit of 10% of the installed costs (up to $50 limit) is available for installing a system with an advanced main air circulating fan.

But you have to hurry because these tax credits are only available for improvements made in 2011. Not taking advantage of this incentive just leaves money on the table.

What Is Considered a High Efficiency Unit?
A split system central air conditioner must meet or exceed 16 SEER and 13 EER; package system central air conditioners must meet or exceed 14 SEER and 12 EER.

An air source heat pump must meet or exceed 15 SEER and 12.5 EER and 8.5 HSPF, in order to qualify for the tax credit. Package heat pump systems must meet or exceed 14 SEER and 12 SEER and 8 HSPF.

Natural gas furnaces, propane furnaces, natural gas hot water boilers, propane hot water boilers, oil furnaces, and oil hot water boilers all must meet or exceed 95% AFUE.

If I claimed more than $500 in tax credits under the previous tax credit programs, am I still eligible?
No. The new law reinstates the lifetime tax credit limits, which disqualify any homeowner who has claimed more than $500 in 25c tax credits since January 1, 2005, from any further credits.