Does my Mitubishi high efficiency energy star split system qualify for an energy saving improvement

Possibly. First of all, the unit must be in the highest efficiency rating group as defined by the standards of the Consortium for Energy Efficiency (CEE) as in effect on January 1, 2009.  This is not the same as an energy star rating, you may have to check with the manufacturer or the installer to see if your unit meets the efficiency requirement.

Then, the credit for installing an efficient air conditioner is 10% of the cost, including labor, up to a maximum of $300. There is also a lifetime maximum of $500 for all such energy efficient credits, so if you have claimed the efficient credit before, your credit now may be limited or used up.  (There is a $500 lifetime maximum for the non-business energy property credit, which covers efficient air conditioners, furnaces, doors, windows, and insulation. This is separate from the energy efficient credit that covers solar panels, fuel cells, and other alternative energy sources which does not have a lifetime cap.)

finally, the credit is nonrefundable, which means that he can only reduce the tax you owe and can’t be added to your refund if you go no income tax. If your income tax for this year is zeroed out by the stimulus, the expanded child tax credit or your low income, you won’t get a benefit from claiming the credit.

Entering Qualified Energy-Saving Improvements:

You can enter them in the Deductions & Credits section:

1. Open your return.
2. Search for energy improvements. (Don't search for energy credit as this will take you to the wrong place.)
3. Click the Jump to energy improvements.
4. At the bottom of the Energy-Saving Home Improvements screen, answer Yes and continue. Follow the instructions.
   1. Page 1 of the interview covers solar, geothermal, wind, and fuel cell. If you're looking for other improvements, like doors, windows, furnace, air conditioning, or heat pump, just keep going to the next page.