How much electricity does an appliance use? Calculate energy cost.
Where a household's electricity actually goes
Consumption is wattage times hours, and the surprise is always which appliances dominate. It is almost never the ones people worry about — lighting and gadgets are rounding errors next to anything that heats, cools or dries.
How it works
- Converts an appliance's power rating and daily hours into annual kilowatt-hours.
- Expresses each figure as a share of a typical household total, so the comparison is proportional rather than abstract.
- Handles continuous loads like fridges and standby separately from occasional ones like a dryer.
annual kWh = (watts ÷ 1000) × hours per day × 365 for seasonal use, replace 365 with the days actually used typical household total: around 3,500 kWh a year share = appliance kWh ÷ household total
Worked example
Five loads compared on the same basis, against a 3,500 kWh annual household.
- LED bulb, 9 W for 5 h/day → 16.4 kWh (0.5%)
- fridge, averaging 30 W continuously → 263 kWh (7.5%)
- standby loads totalling 50 W continuously → 438 kWh (12.5%)
- electric shower, 8,500 W for 10 min/day → 517 kWh (14.8%)
- tumble dryer, 2,500 W for 1 h/day → 913 kWh (26.1%)
The dryer alone is a quarter of the household total, and standby is twenty-six times the bulb. Chasing lighting while running a dryer daily is optimising the wrong end of the list by two orders of magnitude.
Reading the result
- Duty cycle matters more than the nameplate. A fridge labelled 100 W does not draw 100 W continuously — the compressor cycles, averaging perhaps 30 W. A kettle labelled 3,000 W really does draw 3,000 W, but only for three minutes.
- Standby is real but modest. Fifty watts of always-on devices is 438 kWh a year, which is worth eliminating, but a single tumble dryer used daily exceeds it twice over. Fix the big things first.
- Seasonal loads need seasonal arithmetic. An electric heater at 2,000 W for 5 hours across a 120-day winter is 1,200 kWh — using 365 days instead would overstate it threefold.
- Measure rather than estimate when it matters. A plug-in energy monitor costs little and settles arguments about a specific appliance far better than any nameplate figure.
Common questions
- Is leaving devices on standby actually expensive?
- Modestly. Fifty watts of standby is 438 kWh a year — real money, and worth a switched extension lead. But it is smaller than one daily tumble dryer cycle, so it should not be the first thing you tackle.
- Why does my bill not match this calculation?
- Usually heating or hot water, which dominate most bills and are easy to leave out of an appliance-by-appliance tally. Standing charges and a tariff that differs from the headline rate account for most of the rest.