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Energy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical , electric power , mechanical work , light (radiation), or heat .
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
Electric kettle: more than 90% [citation needed] (comparatively little heat energy is lost during the 2 to 3 minutes a kettle takes to boil water). A premium efficiency electric motor: more than 90% (see Main Article: Premium efficiency). A large power transformer used in the electrical grid may have efficiency of more than 99%. Early 19th ...
Thermal energy: joule (J) L 2 M T −2: Heat capacity: C p: Energy per unit temperature change J/K L 2 M T −2 Θ −1: extensive Heat flux density: ϕ Q: Heat flow per unit time per unit surface area W/m 2: M T −3: Illuminance: E v: Wavelength-weighted luminous flux per unit surface area lux (lx = cd⋅sr/m 2) L −2 J: Impedance: Z
For a heat engine, thermal efficiency is the ratio of the net work output to the heat input; in the case of a heat pump, thermal efficiency (known as the coefficient of performance or COP) is the ratio of net heat output (for heating), or the net heat removed (for cooling) to the energy input (external work). The efficiency of a heat engine is ...
A realistic indication of energy efficiency over an entire year can be achieved by using seasonal COP or seasonal coefficient of performance (SCOP) for heat. Seasonal energy efficiency ratio (SEER) is mostly used for air conditioning. SCOP is a new methodology which gives a better indication of expected real-life performance of heat pump ...
kinetic energy: joule (J) wave vector: radian per meter (m −1) Boltzmann constant: joule per kelvin (J/K) wavenumber: radian per meter (m −1) stiffness: newton per meter (N⋅m −1) ^ Cartesian z-axis basis unit vector unitless angular momentum
Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier into kinetic energy or work.