Energy Consumption Calculator
Energy consumption calculator — kWh calculator. Enter an appliance's power consumption in watts (W) or kilowatts (kW) and its hours of use per day, then press Calculate to get the energy E consumed per day, per month (30 days) and per year (365 days) in kilowatt-hours (kWh). Pick a typical appliance from the list for orientation. Everything runs locally in your browser.
Enter the power consumption
Read the power rating off the appliance nameplate (for example 60 W for an LED lamp, 1200 W for a kettle, 1.5 kW for an air conditioner) and type it in. Keep the unit on watts (W) or switch the select to kilowatts (kW) — kilowatts are multiplied by 1000 before the calculation.
Enter hours of use per day
Type the number of hours the device runs each day — 8 for a working-day desktop, 0.25 for a 15-minute kettle routine. Fractions are fine; values start at 0 and are typically up to 24 h/day. The typical-appliance select is a reference list only and never changes the math.
Press Calculate, read kWh
Energy appears as kWh/day, kWh/month (×30 days) and kWh/year (×365 days) at once. Copy any of the three values to your clipboard, or press Reset to clear everything and start over.
How energy consumption is calculated
- What is the energy consumption formula?
- The energy E in kilowatt-hours (kWh) per day is equal to the power P in watts (W) times number of usage hours per day t divided by 1000 watts per kilowatt: E(kWh/day) = P(W) × t(h/day) / 1000 (W/kW).
- How are the month and year figures derived?
- The monthly figure is the daily energy times 30 days, and the yearly figure is the daily energy times 365 days. A 60 W lamp burning 8 h/day uses 0.48 kWh/day, 14.4 kWh/month and 175.2 kWh/year.
- Can I enter power in kilowatts?
- Yes. Switch the power unit select to kilowatts (kW) and the value is multiplied by 1000 first: a 1.5 kW air conditioner running 4 h/day gives 1500 × 4 / 1000 = 6 kWh/day, 180 kWh/month and 2190 kWh/year.
- What about small fractional usage?
- Fractions of an hour work like any decimal. A 1200 W kettle used 15 minutes a day (0.25 h) consumes 1200 × 0.25 / 1000 = 0.3 kWh/day — 9 kWh/month and 109.5 kWh/year.
- Where can I find an appliance’s power rating?
- On the nameplate label or in the manual, usually in watts or amps × volts. Typical values: LED lamp 5–20 W, desktop computer 100–400 W, laptop 50–100 W, refrigerator 100–250 W (averaged over the day), microwave 800–1200 W, electric kettle 1000–2000 W, water heater 2000–4500 W.
Privacy: every calculation runs in your browser tab — no value you type is sent anywhere. Copy buttons use your clipboard only. Results assume constant power draw; real devices cycle, so treat them as estimates. To turn kWh into cost, multiply by your electricity tariff.