A gigajoule (GJ) is a standard measure of energy equal to 10⁹ joules. In the energy sector, it is the primary unit used to price and bill natural gas consumption for commercial and residential customers. One gigajoule contains roughly the same amount of energy as 278 kilowatt-hours of electricity or about 26 liters of heating oil.
Heard on the job
The boiler upgrade should save us about four hundred gigajoules of natural gas per month.