Watts to kWh Calculator
Calculate kilowatt-hours from watts and usage hours for electricity cost estimation. Find out exactly what any appliance costs per day, month, and year based on your electricity rate.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Watts to kWh Calculator | kWh = Watts x Hours / 1,000 | kilowatt-hours |
Step-by-Step Examples
5,000 W dryer, 1 hr/day, $0.13/kWh.
- kWh/day = 5,000 x 1 / 1,000 = 5 kWh
- Monthly = 5 x 30 = 150 kWh
- Monthly cost = 150 x $0.13 = $19.50
100 W TV, 5 hr/day, $0.13/kWh.
- kWh/day = 100 x 5 / 1,000 = 0.5 kWh
- Annual = 0.5 x 365 = 182.5 kWh
- Annual cost = 182.5 x $0.13 = $23.73
1,500 W heater, 8 hr/day, $0.15/kWh.
- kWh/day = 1,500 x 8 / 1,000 = 12 kWh
- Monthly = 12 x 30 = 360 kWh
- Monthly cost = 360 x $0.15 = $54
Real-World Applications
Common Mistakes to Avoid
Watts is a power rating (instantaneous). Watt-hours or kWh is energy (power x time). A 100W bulb running 10 hours uses 1,000 Wh = 1 kWh of energy.
The nameplate wattage is the maximum. Actual usage is often lower. Energy monitors (like Kill-A-Watt) measure real consumption. Use nameplate for quick estimates.
Many appliances draw 1-10W in standby. A TV set-top box drawing 10W 24/7 uses 87.6 kWh/year ($11.40 at $0.13). Multiplied across all standby devices, this adds up.