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Your electricity bill arrives higher than usual and you wonder why. The air conditioner? The water heater? The old fridge? Instead of guessing, you can calculate each appliance’s consumption with a simple formula and see where your money goes.
The basics
- Watt (W): an appliance’s power, printed on its label or in the manual.
- Kilowatt-hour (kWh): the unit on your bill = 1,000 watts for one hour.
The formula
Daily use (kWh) = power in watts × hours of use ÷ 1,000
Monthly cost = daily use × 30 × price per kWh
Example: a 2,000 W electric heater running 3 hours a day: 2,000 × 3 ÷ 1,000 = 6 kWh a day, or 180 kWh a month. At 1.5 per kWh, that’s 270 a month from one appliance.
Try your appliances in the Electricity Cost Calculator, and check the rate on your bill — some countries use tiered pricing that rises with consumption.
What usually uses the most?
| Appliance | Why? |
|---|---|
| Air conditioners and heaters | High power and long running hours |
| Electric water heater | Keeps water hot all day |
| Oven, iron and dryer | Very high power, even for short periods |
| Old refrigerator | Runs 24 hours; older models are less efficient |
| Devices on standby | Small but constant draw |
10 ways to cut your bill
- Set the air conditioner to a moderate temperature; every extra degree of cooling increases use.
- Clean AC filters regularly.
- Put the water heater on a timer instead of running it all day.
- Replace traditional bulbs with LEDs.
- Unplug unused chargers and devices, or use a switched power strip.
- Don’t put hot food straight into the fridge, and keep it away from heat sources.
- Run the washing machine full and at a lower temperature when possible.
- Make the most of daylight and natural ventilation.
- When buying a new appliance, compare energy-efficiency ratings.
- If you have a cheaper night tariff, run large appliances then.
Fuel too
To review transport costs the same way, use the Fuel Cost Calculator — and put what you save into a savings plan.
Bottom line
Watts × hours ÷ 1,000 = kWh. Start by calculating your biggest consumers — that’s where the largest savings lie — then apply simple habits whose effect adds up month after month.
