In February 2018, the U.S. government renewed the 25C tax credit for high-efficiency heating and cooling equipment. This credit is offered as part of a larger energy-efficiency incentive for home improvements. A credit of 10% of the cost of qualified energy-efficient improvements. Qualified improvements include adding insulation, energy-efficient exterior windows and doors, and certain roofs. The cost of installing these items is not included in the credit calculation. Additionally, a credit is available, including the costs of installation, for certain high-efficiency heating and air-conditioning systems, as well as high-efficiency water heaters and stoves that burn biomass fuel. There is a lifetime limitation of $500, of which only $200 may be used for windows.