PWh

PWh, short for petawatt-hour, is a unit of energy used to quantify very large-scale energy flows. It represents 10^15 watt-hours. Because watt-hours are a measure of energy, not instantaneous power, 1 PWh corresponds to a sustained power of one petawatt for one hour. The prefix peta denotes 10^15.

In SI terms, 1 PWh equals 3.6 × 10^18 joules, or 3.6 exajoules (EJ). It also equals 1,000 terawatt-hours (TWh) or 1,000,000 gigawatt-hours (GWh). These conversions help situate the petawatt-hour among more commonly used energy scales.

Usage and context: the petawatt-hour is mainly employed in statistics, planning, and modeling of electricity systems at regional or global scales. It is convenient for expressing annual or multi-year energy totals when the magnitude is too large for smaller units. For individual countries, TWh per year is more common, while PWh per year or for global totals is used in long-term projections and comparisons of national or regional energy demand and supply.

Limitations and note: PWh is not typically used for everyday energy accounting or short-term measurements. It remains a coarse, high-level unit that helps policymakers, researchers, and industry analysts compare energy flows across large systems and long time horizons.