Heating the house, heating water, and the four appliances that make heat: the kettle, the oven, the tumble dryer and the shower. Standby power and phone chargers are a rounding error.
Electricity is billed by the kilowatt hour, so what matters is power multiplied by time. Anything that turns electricity directly into heat draws kilowatts. Anything that processes information draws watts.
- Expensive: central heating, immersion heaters, electric heaters, tumble dryers, electric showers, ovens, kettles.
- Moderate: washing machines and dishwashers, almost entirely because they heat water.
- Cheap: televisions, computers, lighting, routers, chargers, anything on standby.
A modern television left on all evening costs a few pence. An electric heater on for the same period costs more than a pound. The advice to unplug chargers has survived because it sounds virtuous, not because it saves anything.
One genuine exception: an old fridge or freezer that runs constantly with worn seals can cost a surprising amount, because it runs 24 hours a day every day. Age matters more than the plate rating.
The bill is kilowatt hours, and heat is the only household job that needs kilowatts. This one rule survives every price change and tells you what to look at first.
Energy figures are worked from the Ofgem price cap on the date shown and from typical power for the appliance class, not from a named model. Your own rate and your own rating plate are the ones that count. Full disclaimer.