Units of energy - wikipedia Units of energy 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 2015 ) Because energy is defined via work, the SI unit for energy is the same as the unit of work -- the joule ( J ), named in honor of James Prescott Joule and his experiments on the mechanical equivalent of heat. In slightly more fundamental terms, 1 joule is equal to 1 newton metre and, in terms of SI base units 1 J = 1 k g ( m s ) 2 = 1 k g ⋅ m 2 s 2 ( displaystyle 1 mathrm ( J ) = 1 mathrm ( kg ) left ( ( \frac ( mathrm ( m ) ) ( mathrm ( s ) ) ) \right ) ^ ( 2 ) = 1 ( \frac ( mathrm ( kg ) cdot mathrm ( m ) ^ ( 2 ) ) ( mathrm ( s ) ^ ( 2 ) ) ) ) An energy unit that is used in atomic physics, particle physics and high energy physics is the electronvolt ( eV ). One eV is equivalent to 1.60217653 × 10 J. In spectroscopy the unit cm = 0.000123986 eV is used to represent energy since energy is inversely proportional to wavelength from the equation E = h ν = h c / λ ( displaystyle E = h \nu = hc / lambda ). In discussions of energy production and consumption, the units barrel of oil equivalent and ton of oil equivalent are often used. When discussing amounts of energy released in explosions or bolide impact events, the TNT equivalent unit is often used. Contents 1 US units 2 Electricity 3 Natural gas 4 Food industry 5 Atom physics and chemistry 6 Spectroscopy 7 Explosions 8 See also 9 References US units The imperial / U.S. units for both energy and work include the foot - pound force ( 1.3558 J ), the British thermal unit ( BTU ) which has various values in the region of 1055 J, the horsepower - hour ( 2.6845 MJ ), and the gasoline gallon equivalent ( about 120 MJ ). Electricity The energy unit used for everyday electricity, particularly for utility bills, is the kilowatt - hour ( kWh ) ; one kWh is equivalent to 3.6 × 10 J ( 3600 kJ or 3.6 MJ ). Electricity usage is often given in units of kilowatt - hours per year ( kWh / yr ). This is actually a measurement of average power consumption, i.e., the average rate at which energy is transferred. One kWh / yr is about 0.11 watts. Natural gas Natural gas in the US is sold in Therms or 100 cubic feet ( 100 ft = 1 Ccf ). One Therm is equal to about 105.5 megajoules. In Australia, natural gas is sold in megajoules. In the most of the world, natural gas is sold in gigajoules. Food industry The calorie equals the amount of thermal energy necessary to raise the temperature of one gram of water by 1 Celsius degree, from a temperature of 14.5 degrees Celsius, at a pressure of 1 atm. For thermochemistry a calorie of 4.184 J is used, but other calories have also been defined, such as the International Steam Table calorie of 4.1868 J. Food energy is measured in large calories or kilocalories, often simply written capitalized as `` Calories '' ( = 10 calories ). Atom physics and chemistry In physics and chemistry, it is still common to measure energy on the atomic scale in the non-SI, but convenient, units electronvolts ( eV ). The Hartree ( the atomic unit of energy ) is commonly used in calculations. Historically Rydberg units have been used. Spectroscopy In spectroscopy and related fields it is common to measure energy levels in units of reciprocal centimetres. These units ( cm ) are strictly speaking not energy units but units proportional to energies, with h c ∼ 2 ⋅ 10 − 23 J c m ( displaystyle hc sim 2 cdot 10 ^ ( - 23 ) mathrm ( J ) mathrm ( cm ) ) being the proportionality constant. Explosions A gram of TNT releases 980 -- 1100 calories upon explosion. To define the tonne of TNT, this was arbitrarily standardized by letting 1000 thermochemical calories = 1 gram TNT = 4184 J ( exactly ). See also Energy portal Energy consumption Conversion of units of temperature Conversion of units # Energy, work, or amount of heat List of unusual units of measurement Orders of magnitude ( energy ) References Jump up ^ `` CCCBDB What 's a cm - 1 ? ''. Cccbdb.nist.gov. Retrieved 2013 - 11 - 13. Jump up ^ NIST Guide for the Use of the International System of Units ( SI ) : Appendix B8 -- Factors for Units Listed Alphabetically Energy Fundamental concepts Energetics Energy Units Energy system Energy transformation Mass Mass -- energy equivalence Power Thermodynamics Laws of thermodynamics Exergy Forms Kinetic Potential Mechanical Electric Magnetic Gravitational Chemical Ionization Nuclear Chromodynamic Elastic Mechanical wave Sound wave Radiant Rest Thermal Energy carriers Enthalpy Fuel fossil fuel Heat Work Electricity Battery Capacitor Primary energy Fossil fuel Coal Petroleum Natural gas Gravitational energy Nuclear fuel Natural uranium Radiant energy Solar Wind Bioenergy Hydropower Marine energy Geothermal Energy system components Energy engineering Oil refinery Fossil - fuel power station Cogeneration Integrated gasification combined cycle Nuclear power Nuclear power plant Radioisotope thermoelectric generator Solar power Photovoltaic system Concentrated solar power Solar thermal energy Solar power tower Solar furnace Wind power Wind farm High - altitude wind power Hydropower Hydroelectricity Wave farm Tidal power Biomass Geothermal power Use and supply Energy consumption World energy consumption Energy security Energy conservation Efficient energy use Transport Agriculture Renewable energy Sustainable energy Energy policy Energy development Worldwide energy supply South America USA Mexico Canada Europe Asia Africa Australia Misc. Jevons 's paradox Carbon footprint Retrieved from `` https://en.wikipedia.org/w/index.php?title=Units_of_energy&oldid=805973992 '' Categories : Units of energy Conversion of units of measurement Hidden categories : Articles needing additional references from August 2015 All articles needing additional references Talk Contents About Wikipedia Català فارسی עברית 日本 語 Português کوردی Svenska Tiếng Việt Edit links This page was last edited on 18 October 2017, at 20 : 48. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: the unit of energy used to quantify the amount of energy in food is
Answer: calorie