<Table> <Tr> <Td> </Td> <Td> This article is missing information about clear definition of the energy conversion efficiency for light sources . The numbers listed for some light sources are unclear as to whether they refer to conversion efficiency or luminous efficiency . Please help by clarifying the percentages...Please expand the article to include this information . Further details may exist on the talk page . (March 2018) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article is missing information about clear definition of the energy conversion efficiency for light sources . The numbers listed for some light sources are unclear as to whether they refer to conversion efficiency or luminous efficiency . Please help by clarifying the percentages...Please expand the article to include this information . Further details may exist on the talk page . (March 2018) </Td> </Tr> <Table> <Tr> <Th> Conversion process </Th> <Th> Conversion type </Th> <Th> Energy efficiency </Th> </Tr> <Tr> <Td_colspan="3"> Electricity generation </Td> </Tr> <Tr> <Td> Gas turbine </Td> <Td> Chemical to electrical </Td> <Td> up to 40% </Td> </Tr> <Tr> <Td> Gas turbine plus steam turbine (combined cycle) </Td> <Td> Chemical / thermal to electrical </Td> <Td> up to 60% </Td> </Tr> <Tr> <Td> Water turbine </Td> <Td> Gravitational to electrical </Td> <Td> up to 90% (practically achieved) </Td> </Tr> <Tr> <Td> Wind turbine </Td> <Td> Kinetic to electrical </Td> <Td> up to 59% (theoretical limit) </Td> </Tr> <Tr> <Td> Solar cell </Td> <Td> Radiative to electrical </Td> <Td> 6--40% (technology - dependent, 15 - 20% most often, 85--90% theoretical limit) </Td> </Tr> <Tr> <Td> Fuel cell </Td> <Td> Chemical to electrical </Td> <Td> up to 85% </Td> </Tr> <Tr> <Td> World Electricity generation 2008 </Td> <Td> Gross output 39% </Td> <Td> Net output 33% </Td> </Tr> <Tr> <Td_colspan="3"> Electricity storage </Td> </Tr> <Tr> <Td> Lithium - ion battery </Td> <Td> Chemical to electrical / reversible </Td> <Td> 80--90% </Td> </Tr> <Tr> <Td> Nickel - metal hydride battery </Td> <Td> Chemical to electrical / reversible </Td> <Td> 66% </Td> </Tr> <Tr> <Td> Lead - acid battery </Td> <Td> Chemical to electrical / reversible </Td> <Td> 50--95% </Td> </Tr> <Tr> <Td_colspan="3"> Engine / motor </Td> </Tr> <Tr> <Td> Combustion engine </Td> <Td> Chemical to kinetic </Td> <Td> 10--50% </Td> </Tr> <Tr> <Td> Electric motor </Td> <Td> Electrical to kinetic </Td> <Td> 70--99.99% (> 200 W); 50--90% (10--200 W); 30--60% (<10 W) </Td> </Tr> <Tr> <Td> Turbofan </Td> <Td> Chemical to kinetic </Td> <Td> 20 - 40% </Td> </Tr> <Tr> <Td_colspan="3"> Natural process </Td> </Tr> <Tr> <Td> Photosynthesis </Td> <Td> Radiative to chemical </Td> <Td> up to 6% </Td> </Tr> <Tr> <Td> Muscle </Td> <Td> Chemical to kinetic </Td> <Td> 14--27% </Td> </Tr> <Tr> <Td_colspan="3"> Appliance </Td> </Tr> <Tr> <Td> Household refrigerator </Td> <Td> Electrical to thermal </Td> <Td> low - end systems ~ 20%; high - end systems ~ 40--50% </Td> </Tr> <Tr> <Td> Incandescent light bulb </Td> <Td> Electrical to radiative </Td> <Td> 0.7--5.1%, 5--10% </Td> </Tr> <Tr> <Td> Light - emitting diode (LED) </Td> <Td> Electrical to radiative </Td> <Td> 4.2--53% </Td> </Tr> <Tr> <Td> Fluorescent lamp </Td> <Td> Electrical to radiative </Td> <Td> 8.0--15.6%, 28% </Td> </Tr> <Tr> <Td> Low - pressure sodium lamp </Td> <Td> Electrical to radiative </Td> <Td> 15.0--29.0%, 40.5% </Td> </Tr> <Tr> <Td> Metal - halide lamp </Td> <Td> Electrical to radiative </Td> <Td> 9.5--17.0%, 24% </Td> </Tr> <Tr> <Td> Switched - mode power supply </Td> <Td> Electrical to electrical </Td> <Td> currently up to 96% practically </Td> </Tr> <Tr> <Td> Electric shower </Td> <Td> Electrical to thermal </Td> <Td> 90--95% (multiply with the energy efficiency of electricity generation for comparison with other water - heating systems) </Td> </Tr> <Tr> <Td> Electric heater </Td> <Td> Electrical to thermal </Td> <Td> ~ 100% (essentially all energy is converted into heat, multiply with the energy efficiency of electricity generation for comparison with other heating systems) </Td> </Tr> <Tr> <Td_colspan="3"> Others </Td> </Tr> <Tr> <Td> Firearm </Td> <Td> Chemical to kinetic </Td> <Td> ~ 30% (. 300 Hawk ammunition) </Td> </Tr> <Tr> <Td> Electrolysis of water </Td> <Td> Electrical to chemical </Td> <Td> 50--70% (80--94% theoretical maximum) </Td> </Tr> </Table> <Tr> <Th> Conversion process </Th> <Th> Conversion type </Th> <Th> Energy efficiency </Th> </Tr>

What percentage of energy usage by muscles is converted into heat energy