Achieving greater energy efficiency means using less energy to do the same amount of work.

Houses can achieve big energy savings through efficiency. About 43 percent of the energy consumed in the United States is used for residential heating and cooling, and almost 12 percent is used for residential lighting. Most U.S. homes are not very energy-efficient. Compared to the average home, an energy-efficient home can save up to 40 percent on energy by installing efficient heating and cooling systems, light fixtures, adequate insulation and high-performance windows.

Figure 12 Residential energy distribution Source: U.S. Department of Energy, 2004