Convert common energy (power) units to joules (watts) with the following table.

Find the units of your energy (power) in the left column, and then use the multiplier in the right column with the amount of energy (power) you have in those units to determine how many equivalent joules (watts) there are. (Remember, 1 joule/second = 1 watt.) For instance, if you have 10 therms, use 105,500,000 as the multiplier to get 1,055,000,000 joule, or 1.055 GJ (G = giga; J = joule).

1 kilowatt-hour (kwh) 3.6*106 joules
1 British thermal unit (Btu) 1,055 joules
1 therm (= 100,000 Btu) 105.5*106 joules
1 erg 0.1*10-6 joules
1 calorie (thermochemical) 4.184 joules
1 Calorie (food calorie) 4,187 joules
1 quad 1.055*1018 joules
1 amp-hour-volt 3,600 joules
1 horsepower (hp) 745.7 watts
1 Btu/hour 0.2931 watts
1 ft-lb/sec 1.356 watts