Joule power

The “watt” is named for James Watt, but it is not “the standard measure of electricity” (“Scots engineer Watt graces new £50 banknote”, 1 October). The watt (W) is the modern unit of power, the rate of energy use, and is more familiar in its thousand multiple: the kilowatt (kW).

You have been misled by the historical adoption of this unit by the electricity industry and its development as the kilowatt-hour (kWh), a specialised energy unit (the unit of electricity). Unfortunately, the latter unit has been adopted by energy suppliers, not just for electricity but for gas. They should be using the joule.

STEUART CAMPBELL

Dovecot Loan

Edinburgh