What this calculator does
The Daily Electricity Usage Calculator turns an appliance's power rating into the energy it actually consumes. Enter the device wattage, how many hours it runs each day, and your electricity price per kWh, and you instantly see the energy used and cost per day, month, and year. It works for any appliance worldwide — just use your local cost per kilowatt-hour.
How to use it
Find the wattage on the appliance label or in its manual (e.g. a 100 W bulb, a 1500 W heater). Enter the number of hours you typically use it each day. Then enter the price you pay per kWh — check a recent electricity bill. The calculator shows kWh per day along with monthly (30-day) and yearly (365-day) totals and costs.
The formula explained
Energy in kilowatt-hours equals power in watts multiplied by hours of use, divided by 1000 (since 1 kW = 1000 W):
$$\text{kWh/day} = \frac{\text{Watts} \times \text{hours/day}}{1000}$$
Cost simply multiplies that energy by your rate: $$\text{Cost/day} = \text{kWh/day} \times \text{rate}$$ Monthly and yearly figures scale the daily value by 30 and 365.
Worked example
A 100 W light bulb running 5 hours a day at $0.15 per kWh: $$\text{kWh/day} = \frac{100 \times 5}{1000} = 0.5\ \text{kWh}$$ $$\text{Cost/day} = 0.5 \times \$0.15 = \$0.075$$ Over a year that is \(182.5\) kWh and about \(\$27.38\).
FAQ
Where do I find the wattage? It's usually printed on a label on the appliance or in the manual. Some devices list amps and volts instead — multiply them (\(\text{W} = \text{A} \times \text{V}\)).
What rate should I enter? Use your effective cost per kWh from your latest electricity bill, including any per-unit charges.
Why use 30 and 365 days? These are standard averages for monthly and yearly estimates; actual months vary slightly.
