Estimate your electricity use and bill from a list of appliances, their wattage and hours of use, and see which ones cost most.
Quantity is optional and defaults to 1. Wattage is on the appliance label.
Enter the values to see the result here.
Formula
For each appliance with power P watts, h hours per day, quantity q and a period of D days:
E=1000P×h×q×DkWh
The energy cost is the total kWh times the tariff t, and the bill adds any fixed charge F:
bill=t∑E+F
Each appliance’s share is its kWh divided by the total, which shows where the money goes.
Worked example
A 1,500 W air conditioner for 8 hours a day over 30 days, with a tariff of 0.18 per kWh.
Energy: 1500×8×30/1000=360 kWh.
Cost: 360×0.18=64.80.
Add a 150 W refrigerator running 8 hours: 150×8×30/1000=36 kWh, costing 6.48. The air conditioner uses ten times more than the refrigerator and dominates the bill.
Common mistakes
Entering kilowatts in the watts column. A 2 kW heater is 2,000 W.
Using nameplate hours for appliances that cycle.
Forgetting standby power, which can be 3 to 10 W per device left plugged in.
Ignoring that tariffs often rise in bands as consumption grows.
Frequently asked questions
Where do I find an appliance's wattage?
On the rating label on the back or underside, marked W or kW. If only amps and volts are shown, multiply them: 5 A at 220 V is 1,100 W. Air conditioners and heaters are the big ones, often 1,000 to 3,000 W.
A fridge or AC cycles on and off. What hours should I enter?
Enter the hours it actually runs. A fridge draws power about a third to half of the day, so 8 to 12 h is realistic. An air conditioner that is "on" for 10 hours may run its compressor only 6 to 7 of them.
Why does my real bill differ from the estimate?
Real bills may use tiered prices, taxes, fuel surcharges and a fixed meter fee, and appliance power draw changes with age. The fixed-charge box covers the flat part; for tiers, calculate each band yourself.
How can I lower the bill?
Start with the top rows of the results table. Raising an air-conditioner setpoint by 1 °C typically cuts its use by 6 to 8%, and replacing a 60 W incandescent bulb with a 9 W LED saves about 15 kWh a month at 10 hours a day.