Convert petajoule to petawatt hour

The watt (W) is a unit of power, the rate at which energy is used or produced. The watt-hour (Wh) is a unit of energy, one watt sustained for one hour, and is what this page converts: a 2 kW heater running for 3 hours uses 6 kWh, and an electricity bill counts kWh. 'Watts per hour' (W/h) would be a rate of change of power, is rarely needed, and is not the same thing as a watt-hour.

The joule is tiny, so the everyday unit is the megajoule: 1 kWh is 3.6 MJ, a litre of petrol holds about 33 MJ and a litre of diesel 36, and Australian and New Zealand food labels count in kilojoules towards a daily 8,700 kJ (8.7 MJ). Gas bills in Canada are in gigajoules, 1 GJ being 278 kWh or roughly 26 m³ of gas, and a full 50-litre tank of petrol is 1.7 GJ. National statistics use petajoules and exajoules: the UK consumes around 7 EJ of primary energy a year, the world some 620 EJ.