Power use and Heat

Sorry, that should be £1 per watt _per annum_ of course, ie over a year's usage switching off
something that wastes 100 watts saves you about £100. If it wastes 100 watts for 6 hours per
day, that's £25. It's a rule of thumb, so your specific tariffs may be rather different
depending on the mixture of fixed versus variable costs, but probably not by an order of
magnitude.