Electricity Cost / kWh Calculator
Calculate how much electricity an appliance uses per month and what it costs.
Enter watts, hours per day, and your electricity rate.
Electricity is billed in kilowatt-hours (kWh) — a unit of energy equal to running a 1,000-watt appliance for 1 hour continuously.
Energy consumption formula: Energy (kWh) = Power (watts) ÷ 1000 × Time (hours)
Cost formula: Cost = Energy (kWh) × Rate ($/kWh)
Combined formula: Cost = (Watts ÷ 1000) × Hours × Rate
Worked example: A desktop PC draws 200W and runs 8 hours per day. Electricity costs $0.15/kWh. Daily Energy = (200 ÷ 1000) × 8 = 1.6 kWh Daily Cost = 1.6 × $0.15 = $0.24/day Monthly Cost = $0.24 × 30 = $7.20/month Annual Cost = $0.24 × 365 = $87.60/year
Common appliance power draw (approximate):
| Appliance | Watts | Cost/hour at $0.15 |
|---|---|---|
| LED bulb | 10 W | $0.0015 |
| Laptop | 45–80 W | $0.007–$0.012 |
| Desktop PC | 150–300 W | $0.022–$0.045 |
| Refrigerator | 100–400 W | varies (compressor cycles) |
| Air conditioner | 1,000–3,500 W | $0.15–$0.53 |
| Electric oven | 2,000–5,000 W | $0.30–$0.75 |
| EV charger (L2) | 7,200 W | $1.08 |
Average US electricity rates (2024): $0.12–$0.18/kWh residential, varying by state.
Hawaii is highest ($0.37/kWh); Louisiana and Idaho are among the lowest ($0.09–$0.10/kWh).
Standby power (“vampire power”): Devices left on standby collectively consume 5–10% of a typical home’s electricity. Smart power strips eliminate this waste.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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