<P> 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 . </P> <P> 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 . </P> <P> 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). </P> <P> 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 . </P>

The unit of energy used to quantify the amount of energy in food is