The kilojoule (kJ) equals 1,000 joules and is the standard unit for expressing food energy content and chemical reaction energies in countries using the metric system. Food labels in Australia, Europe, and many other regions display energy values in kilojoules alongside or instead of calories. One kilojoule equals approximately 238.8 calories or about 0.239 kilocalories.

The watt-hour (Wh) equals 3,600 joules, representing the energy consumed by a one-watt device operating for one hour. It is commonly used for small battery capacities, solar panel output ratings, and electric vehicle charging metrics where kilowatt-hours would be too large a unit. One watt-hour equals exactly 0.001 kilowatt-hours or about 3.412 BTU.