What this calculator does
This Electricity Usage Calculator turns an appliance's power rating and how long you run it each day into an estimated monthly electricity cost. It works for any device that lists wattage — heaters, air conditioners, refrigerators, TVs, gaming PCs, water pumps, lights and more — and uses your own local electricity rate, so it applies to any country.
How to use it
Enter the appliance power in watts (check the label or nameplate), how many hours it runs per day, the number of days you want to count in the month, and your electricity rate per kilowatt-hour (kWh) from your utility bill. The calculator returns the monthly cost plus the daily cost and the energy consumed.
The formula explained
Electricity is billed per kilowatt-hour. One kWh is 1,000 watts running for one hour. So we first convert watts to kilowatts (divide by 1,000), multiply by hours per day to get daily kWh, multiply by days to get monthly kWh, then multiply by your rate:
$$\text{Monthly Cost} = \frac{\text{Watts}}{1000} \times \text{Hours/day} \times \text{Days} \times \text{Rate}$$
Worked example
A 1,500 W space heater used 5 hours a day for 30 days at $0.15/kWh: \((1500 \div 1000) = 1.5\) kW. \(1.5 \times 5 = 7.5\) kWh per day. \(7.5 \times 30 = 225\) kWh per month. \(225 \times \$0.15 =\) $33.75 per month.
FAQ
Where do I find the wattage? It's usually printed on the appliance label, nameplate, or in the manual. If only amps and volts are listed, multiply them (\(W = V \times A\)).
What rate should I use? Use the per-kWh price on your electricity bill. Some plans have tiered or time-of-use rates — use your average for a rough estimate.
Is this exact? It's an estimate. Real usage varies with how the device cycles on and off (e.g. fridges and ACs), so actual costs may differ.
