Electricity Units (kWh) Calculator
Convert an appliance's wattage and usage time into units (kWh) — the number your electricity meter counts.
Updated
Formula
Units (kWh) = Watts × Quantity × Hours/day × Days ÷ 1000
Divide by 1,000 because a unit is a kilowatt-hour, and 1 kW = 1,000 W.
Examples
LED bulb 12 W, 6 h/day, 30 days
12 W × 1 × 6 h × 30 days = 2.16 units (kWh)
10 LED bulbs, 6 h/day
12 W × 10 × 6 h × 30 days = 21.6 units (kWh)
Refrigerator 150 W average, 24 h
150 W × 1 × 24 h × 30 days = 108 units (kWh)
Reference table
| Hours per day | Units per day | Units per month |
|---|---|---|
| 1 | 1 | 30 |
| 2 | 2 | 60 |
| 4 | 4 | 120 |
| 6 | 6 | 180 |
| 8 | 8 | 240 |
| 12 | 12 | 360 |
| 24 | 24 | 720 |
Important information
- Appliances with thermostats (AC, fridge, iron, geyser) cycle on and off, so average watts are lower than the rating.
- Your meter's monthly reading minus last month's reading equals units used.
Frequently asked questions
How many units does a 1,000 watt appliance use in an hour?
Exactly 1 unit.
How many units does a fan use per month?
An 80 W ceiling fan running 12 hours a day uses about 28.8 units a month; a 35 W DC fan uses about 12.6.
How many units does a fridge use?
Typically 80–150 units a month depending on size, age and whether it is an inverter model.
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