Question: what percentage of energy usage by muscles is converted into heat energy
Answer: 99 % ( > 200 W ) ; 50 -- 90 % ( 10 -- 200 W ) ; 30 -- 60 % ( < 10 W ) Turbofan Chemical to kinetic 20 - 40 % Natural process Photosynthesis Radiative to chemical up to 6 % Muscle Chemical to kinetic 14 -- 27 % Appliance Household refrigerator Electrical to thermal low - end systems ~ 20 % ; high - end systems ~ 40 -- 50 % Incandescent light bulb Electrical to radiative 0.