<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (August 2008) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (August 2008) (Learn how and when to remove this template message) </Td> </Tr> <P> 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 . </P> <P> Energy conversion efficiency depends on the usefulness of the output . All or part of the heat produced from burning a fuel may become rejected waste heat if, for example, work is the desired output from a thermodynamic cycle . Energy converter is an example of an energy transformation . For example a light bulb falls into the categories energy converter . η = P o u t P i n (\ displaystyle \ eta = (\ frac (P_ (\ mathrm (out))) (P_ (\ mathrm (in))))) Even though the definition includes the notion of usefulness, efficiency is considered a technical or physical term . Goal or mission oriented terms include effectiveness and efficacy . </P>

Ratio of useful energy to total input energy