What this calculator does
The Appliance Electricity Cost Calculator estimates how much it costs to run any electrical device. Manufacturers list power draw in watts (W) on the appliance label, while energy providers bill you in kilowatt-hours (kWh). This tool bridges the two so you can see the daily, monthly and yearly running cost of a heater, fridge, computer, air conditioner or any other appliance. It works with any currency — just enter your local price per kWh.
How to use it
Enter the appliance power in watts, how many hours per day it runs, how many days per month you use it, and your electricity rate (cost per kWh, found on your energy bill). The calculator returns the cost per day, per month and per year, plus the energy consumed in kilowatt-hours.
The formula explained
Electricity cost is built from two simple steps. First convert watts to kilowatts by dividing by 1000, then multiply by running hours to get energy used: \(\text{kWh} = (\text{Watts} \div 1000) \times \text{hours}\). Multiply that energy by your price per kilowatt-hour to get cost: \(\text{Cost} = \text{kWh} \times \text{rate}\). Scaling by days per month and 365 days gives the monthly and yearly figures.
$$\text{Monthly Cost} = \frac{\text{Power (W)}}{1000} \times \text{Hours/day} \times \text{Days/month} \times \text{Rate (per kWh)}$$
Worked example
A 1500 W space heater runs 5 hours a day, 30 days a month, at a rate of 0.15 per kWh. Energy per day = \((1500 \div 1000) \times 5 = 7.5\) kWh. Daily cost = \(7.5 \times 0.15 = 1.125\). Monthly cost = \(1.125 \times 30 = 33.75\), and yearly cost = \(1.125 \times 365 = 410.63\).
FAQ
Where do I find the rate per kWh? Look on your electricity bill for the per-unit or per-kWh price; it usually appears alongside your usage charges.
What if my appliance lists amps instead of watts? Multiply amps by your voltage (e.g. 120 V or 230 V) to get watts, then enter that value.
Does this account for standby power? No — it assumes the device draws its rated wattage only while in use. For always-on standby loads, enter the standby wattage and 24 hours per day.
