Making homes, vehicles, and businesses more energy efficient is seen as a largely untapped solution to addressing global warming and energy security. The energy efficiency of a consumer item is generally defined as the relative amount of power used (usually in the form of electricity) by an item in satisfying its purpose. For example, a washing machine is designed to wash clothes. The more energy efficient the washing machine, the less electricity that is consumed in performing this task.

To fully evaluate the energy efficient of a consumer item however, running costs and expected life must be included in the calculation. Energy consumption can be measured per kilogram, for example, when comparing the efficiency of a full washing machine load to a smaller one. Energy Star and the European Union energy label are energy labels system that allow buyers to easily make comparisons between the power consumption statistics of similar electrical appliances.

The state of California began implementing energy-efficiency measures in the mid-1970s, including building code and appliance standards with strict efficiency requirements. As a result, the state's energy consumption has remained flat over 30 years while national U.S. consumption doubled. As part of its strategy, California implemented a three-step plan for new energy resources that puts energy efficiency first, renewable electricity supplies second, and new fossil-fired power plants last. In general, up to 75% of the electricity used in the U.S. today could be saved with efficiency measures that cost less than the electricity itself.