gigajoule

A gigajoule, symbol GJ, is a unit of energy in the International System of Units (SI). It equals 1,000,000,000 joules (10^9 J). The prefix giga- denotes a factor of 1,000,000,000, so a gigajoule is a large unit suitable for expressing substantial energy quantities.

Common conversions place the gigajoule in practical terms: 1 kWh equals 3.6 MJ, so 1 GJ equals 1,000 MJ or about 277.78 kWh (0.2778 MWh). In other energy units, 1 GJ is approximately 947,817 BTU and 0.001 terajoules (TJ). In relation to electrical energy, 1 GJ is about 0.2778 MWh.

Uses and context: the gigajoule is routinely used to express energy content of fuels, heat energy, and large-scale energy production. It is an energy quantity, not a rate; power is measured in watts (joules per second). For example, a 1 gigawatt (GW) power source operating for one second releases 1 GJ of energy, while running at 1 GW for an hour releases about 3.6 GJ.

Relationship to other scales: one gigajoule is 0.001 terajoules, and 0.001 gigajoules equals one megajoule? Careful: 1 GJ = 1,000 MJ. The unit is most useful for mid-to-large energy amounts, such as fuel inventories, industrial heat, and national energy statistics.