Electricity Bill Calculator
Work out the monthly kWh and cost of each appliance, and which ones cost the most.
How it works
Enter each appliance's power in watts, the hours it runs per day and the days per month you use it. Add your rate per kWh. Energy is watts times hours divided by 1000, scaled up by the days used, and cost is that energy times your rate.
kWh per day = watts × hours per day ÷ 1000
kWh per month = kWh per day × days used
Monthly cost = kWh per month × rate per kWhExample
A 1,500 W air conditioner used 6 hours a day for 30 days: 1,500 × 6 ÷ 1000 = 9 kWh a day, so 9 × 30 = 270 kWh a month. At a rate of 8 per kWh that is 270 × 8 = 2,160 a month.
Common mistakes
- Using the wrong unit for power. A label that says 1.5 kW is 1,500 W, so type 1500 in the watts box.
- Counting a fridge or air conditioner as running all day at full power. They switch on and off, so use the hours the compressor actually runs.
- Forgetting standby draw. TVs, chargers and routers use a few watts around the clock. Add them as their own row if you want them counted.
About this calculator
List your appliances with their wattage, the hours you run them each day and the days you use them in a month, then enter your electricity rate per kWh. The calculator gives the energy each appliance uses, what it costs per month, and ranks them from most to least expensive with each one's share of the total.
The rate is whatever you type; the starting figure of 8 is only an example, so use the per-unit price on your own bill. It uses one flat rate. Slab tariffs, fixed charges, taxes and surcharges are not modelled, and appliances that cycle on and off, such as fridges and air conditioners, draw less than their rated wattage on average, so treat the result as an estimate.
Frequently asked questions
How do I find an appliance's wattage?
Look at the label or rating plate on the appliance, which usually lists power in watts (W) or kilowatts (kW). If it only gives volts and amps, multiply them: 230 V × 2 A is about 460 W. The quick-add buttons use typical figures only, so check your own appliance.
What is a unit on my electricity bill?
In India and many other countries one unit on the bill is one kilowatt-hour (kWh): a 1,000 W appliance running for one hour. This calculator multiplies the kWh by the rate you enter.
Why is the total different from my actual bill?
This tool applies one flat rate to the appliances you list. Real bills often add slab pricing, fixed or demand charges, taxes and surcharges, and include appliances you did not list. Cycling appliances also use less than their rated wattage on average.
How do I count an appliance that is not used every day?
Set days per month to the number of days you actually use it. For example, a washing machine used 8 times a month has 8 days. If the hours differ a lot between days, add the appliance twice with different hours and days.