Electricity consumption calculation: from watts to kWh to cost

Short answer: consumption = power (watts) × running time (hours) ÷ 1,000; the result is kilowatt-hours (kWh). Cost = kWh × your unit price. Example: a 2,000 W heater running for 3 hours uses 2,000 × 3 ÷ 1,000 = 6 kWh; at your tariff's price per kWh, the cost is 6 × that price. Use the all-in price per kWh from your bill.

Three steps

1. Find the power: on the rating label or in the manual, in watts (W) or kilowatts (kW). 1 kW = 1,000 W.
2. Convert to kilowatt-hours: W × hours ÷ 1,000 = kWh. For a month, multiply daily hours by the number of days.
3. Convert to money: kWh × unit price. For reference, our calculators use a Turkish household price of about TRY 3.24/kWh (September 30, 2026); in other countries use your own tariff.

Examples

• Electric heater, 2,000 W, 3 hours a day, 30 days: 2,000 × 3 × 30 ÷ 1,000 = 180 kWh.
• LED bulb, 9 W, 5 hours a day, 30 days: 9 × 5 × 30 ÷ 1,000 = 1.35 kWh. An old 60 W incandescent giving the same light would use 9 kWh.
• Air conditioner, about 1,000 W average draw, 8 hours a day, 30 days: about 240 kWh. Inverter units reduce their draw once the room is at temperature, so the real figure is usually lower.
• Fridge: for appliances that cycle on and off, use the annual kWh on the energy label instead of watts. A label of 250 kWh/year means about 21 kWh a month.
• Washing machine and dishwasher: the label's "kWh/100 cycles" ÷ 100 = one wash. E.g. 50 kWh/100 cycles → 0.5 kWh per wash.
• Electric car: a car using 18 kWh per 100 km draws about 20 kWh from the grid including charging losses (~10%). 1,500 km a month → about 300 kWh. Try our charging cost calculator.

No watts on the label? From amps to watts

If the label only shows current (A), approximate power is:

• Single-phase: W ≈ 230 V × A. A 10 A appliance ≈ 2,300 W.
• Three-phase: W ≈ 1.73 × 400 V × A × power factor. Motors have a power factor of about 0.8–0.9.

The label current is often the maximum, not the constant draw. A plug-in energy meter gives an exact reading.

Standby consumption

TVs, routers, set-top boxes, chargers and appliance displays draw power even when off. Each is small (often 0.5–5 W) but it runs all year: a total standby load of 20 W comes to 20 × 24 × 365 ÷ 1,000 ≈ 175 kWh a year. Switched power strips, unplugging unused chargers and timers reduce it.

Effective ways to cut consumption

• Switch lighting to LED: about 6–8 times less energy for the same light (LED bulb types).
• Control lights in shared areas with motion sensors or timers (motion sensor lighting, time switches).
• Thermostats and inverter appliances make a big difference in heating and cooling.
• Charge your EV at home: the price per kWh is lower than at public chargers (public charging prices).

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• → Time switches
• → Home wallboxes
• → Lumens, watts and colour temperature
• → How to calculate lighting
• → Single-phase vs three-phase