petajoule

The petajoule is the unit national energy accounting is written in. When a statistical agency adds up a year of coal, gas, oil, hydro and electricity trade, the totals land in the hundreds or thousands of PJ: Australia publishes its official energy balance entirely in petajoules and runs to roughly 6,000 PJ of primary energy a year, with single industries showing up at a few dozen PJ each. The United States is the holdout, keeping its national totals in quads, and one quad is 1,055 PJ, so the two literatures convert on a factor just over a thousand.

Anchors worth carrying: 1 PJ is 277.8 GWh and just under 24,000 tonnes of oil equivalent, and the strategic megaton of TNT, for a sense of concentration, is 4.184 PJ. The trap in balance work is not the prefix but the boundary. A country's primary energy counts fuel before conversion losses; the electricity its citizens actually meter is far smaller, and comparing one country's primary figure against another's final consumption misleads by tens of percent without a single arithmetic error being made.

The electricity side of the same statistics is kept in TWh, and the bridge is exact: one TWh is 3.6 PJ, because both unwind to the same joule. The energy converters on this site carry that factor exactly, which matters in energy-balance work, where a long chain of unit conversions is the whole calculation and rounding accumulates quietly.