Energy efficiency

Energy efficiency may refer to:


 * Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process
 * Electrical efficiency, useful power output per electrical power consumed
 * Mechanical efficiency, a ratio of the measured performance to the performance of an ideal machine
 * Thermal efficiency, the extent to which the energy added by heat is converted to net work output or vice versa
 * Luminous efficiency, a measure of how well a light source produces visible light
 * Fuel efficiency, the efficiency of converting potential energy in a fuel into kinetic energy
 * Energy efficiency in transportation, the fuel economy of various modes of transportation
 * Energy-efficient landscaping, a type of landscaping designed for the purpose of conserving energy
 * Efficient energy use, minimizing the amount of energy used for a given, constant energy service
 * Energy conservation, reducing energy consumption by using less of an energy service