The tax credit for energy-efficient home improvements has been slashed from $1,500 to $500 and you’ll have to make any qualifying purchase by Dec. 31. But any tax credits are valuable tools. You get a dollar-for-dollar tax reduction for 10% of the cost of insulating, installing efficient windows, replacing old furnaces and air conditioners and making other home energy efficiency improvements—up to $500. The credit for installing efficient windows is capped at $200, furnaces and boilers at $150 and $200, and water and wood heating systems at $300.