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.