exawatt

Exawatt (symbol EW) is the SI unit of power equal to 10^18 watts. The prefix exa- denotes 10^18, so 1 EW is 1,000 petawatts or 1,000,000 terawatts. As a unit of instantaneous power, exawatts measure the rate of energy transfer at a given moment.

In practical terms, exawatts describe scales far larger than current human energy use. The exawatt is used mainly in astrophysical contexts or in discussions of hypothetical, megascale energy processes. Power values do not imply energy by themselves; sustaining 1 EW for a second corresponds to 1 exajoule of energy, and integrating over time yields total energy.

Examples help frame the scale. The Sun’s total power output, its luminosity, is about 3.8×10^26 watts, roughly 3.8×10^8 EW. The power intercepted by the Earth from the Sun is about 174 petawatts, around 0.174 EW. By comparison, human civilization consumes on the order of tens of terawatts (TW), which is about 10^−5 EW, illustrating how far exawatts exceed everyday energy scales.

See also the SI prefixes and related units such as petawatt and terawatt. The exawatt remains mostly a theoretical or astrophysical reference point rather than a common practical unit in engineering or energy planning.