petajoule

Petajoule (PJ) is an SI unit of energy equal to 10^15 joules. The name combines the joule with the SI prefix peta-, which denotes 10^15.

One petajoule is a large quantity of energy. In common conversions, 1 PJ equals 1e15 J, which is approximately 277.8 gigawatt-hours (GWh), 277,778 megawatt-hours (MWh), or 277,778,000 kilowatt-hours (kWh). In terms of other energy scales, 1 PJ is equal to about 0.001 exajoule (EJ) or 0.2778 terawatt-hours (TWh). In energy units used in engineering contexts such as fuel and heating, 1 PJ is roughly 9.48×10^11 British thermal units (BTU).

The petajoule is commonly used to express very large energy quantities such as national annual energy consumption, electricity generation in large power plants, or volumes of natural gas. It provides a convenient middle ground between joules for precise calculations and larger prefixes such as terajoules and exajoules.

The symbol is PJ, with capital P and J. The prefix peta- and the joule unit are both defined by the International System of Units, and PJ is widely used in energy statistics, engineering, and policy discussions.