The residential energy tax credits were set to expire on 12/31/10 for projects such as installing additional insulation, qualified roofs, doors, windows, HVACs, etc.  Congress let the previous rules go away but did add a $500 credit for 2011.  However, there are a bunch of caveats.  The percentage of the credit has been reduced from 30% of expenditures to 10%.  In addition, there are limitations (below the $500 amount) depending upon the type of project that you are implementing.  Finally, if you have claimed over $500 in energy tax credits since 2005 you are not eligible to claim this extended credit in 2011  As always, the bottom line is to look at all the details and be sure that you will qualify before you start on that big product.  With some quick questions your friendly neighborhood tax accountant can help you determine if you will qualify for the 2011 $500 Energy Tax Credit.