What is actually costing you on your electricity bill
Appliance wattage matters far less than how long it runs. Here is what actually drives a bill, and where switching things off genuinely pays.
Electricity bills are unusually hard to reason about because you never see the product. The unit you are charged for — the kilowatt-hour — is one kilowatt drawn for one hour, which means the cost of anything is power multiplied by time. That second term is where almost all the intuition goes wrong.
Wattage alone tells you very little
A kettle draws 2,200 W, more than almost anything else in a house. A fridge draws about 150 W. People assume the kettle dominates the bill. At $0.15 per kWh:
| Appliance | Power | Typical use | Cost per year |
|---|---|---|---|
| Electric heater | 2,000 W | 4 h/day in winter | $438 |
| Fridge | 150 W | Always on | $197 |
| Desktop PC | 200 W | 8 h/day | $88 |
| Kettle | 2,200 W | 15 min/day | $30 |
| Old incandescent bulb | 60 W | 5 h/day | $16 |
| TV on standby | 5 W | Always on | $7 |
| LED bulb | 10 W | 5 h/day | $3 |
The kettle — by far the hungriest device on the list — costs less than a fifth of what the fridge does, because it runs for minutes rather than continuously. Time on beats power drawn, almost every time.
The two categories that actually matter
Once you see it this way, household electricity splits cleanly into two groups, and they need different responses.
- Heating things. Heaters, kettles, ovens, tumble dryers, immersion heaters. Turning electricity into heat is inherently expensive, and these dominate bills in cold months. There is no efficient version — the only lever is using them less, or shorter.
- Everything always on. Fridges, freezers, routers, standby lights. Individually trivial, collectively significant, because 24 hours a day is 8,760 hours a year. This is where small wattages quietly accumulate.
Where the savings really are
Swapping one 60 W incandescent bulb for a 10 W LED saves about $13 a year at five hours daily use. Across fifteen fittings that is close to $200 annually, for a one-off cost recovered within months. Lighting is the rare case where a straight substitution changes the number meaningfully, because the LED does the same job for a sixth of the power.
Heating rewards behaviour rather than hardware. Dropping a 2,000 W heater from four hours a day to three saves about $110 a year. No purchase, no efficiency claim — just an hour.
Working out any appliance yourself
Find the wattage on the label or in the manual. If it lists amps instead, multiply by your mains voltage — 5 A at 230 V is 1,150 W. Then multiply watts by hours, divide by 1,000 for kilowatt-hours, and multiply by your tariff. That is the entire calculation, and it works for anything that plugs in.
One caveat worth knowing: appliances with thermostats — fridges, freezers, heaters — cycle on and off rather than drawing their rated power continuously. A fridge labelled 150 W might average nearer 50 W over a day, so treat rated figures as an upper bound for anything that switches itself.
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