Monday, 30 December 2019

MisMeasuring Energy

When discussing  devices for storing electricity people sometimes try to measure the capacity in megawatts.

A watt measures power, not energy so it would be better to say something like megawatt hours, or megawatt days, though even that is strange.

The units of power are energy/time. A watt = 1 joule per second. Domestic power is usually measured in kilowatt hours.

A kilowatt hour = 1000 joules per second for an hour, involving both division by time and multiplication by time.

Removing both the seconds and the hours we have 1 unit = 3.6*106 joules

People who dislike number can just call it a 'unit'. Those who like precision can avoid the redundant use of units of time.

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