What Does Electricity Actually Cost?
“How much does it cost to run?” beats wattage every time — a 1,500 W heater sounds abstract, but $60 a month gets attention. The math is genuinely simple; what people lack are the two inputs: the appliance's real draw and their true per-kWh rate. Both are findable in minutes.
Enter the wattage (label, spec sheet, or a plug-in power meter), daily hours of actual use, and your rate. You get kWh per day and cost per day, month, and year. Run it per appliance and the mystery items on your bill sort themselves out fast — space heating and cooling almost always win.
Sizing the AC itself rather than running costs? That's the BTU Calculator.
How to Calculate Electricity Cost
One conversion — watts to kilowatt-hours — and a multiplication:
kWh per day = watts × hours ÷ 1,000 Cost = kWh × rate ($/kWh) Month ≈ day × 30 · Year = day × 365
Worked example: a 1,500 W space heater running 8 hours a day uses 12 kWh daily — $2.04 a day at $0.17/kWh, $61.20 a month, $745 a year. The same math prices a 10 W LED bulb at 26 cents a month: wattage differences of 100× produce cost differences of 100×.
Electricity Cost Chart for Common Appliances
Common wattages at typical daily use, priced at a $0.17/kWh example rate — every cost computed by this calculator's formula:
| Appliance | Typical draw | Daily use | Monthly cost |
|---|---|---|---|
| LED bulb | 10 W | 5 h | $0.26 |
| WiFi router | 5 W | 24 h | $0.61 |
| TV (LED, 55″) | 100 W | 4 h | $2.04 |
| Microwave | 900 W | 1 h | $4.59 |
| Window AC | 1,200 W | 3 h | $18.36 |
| Space heater | 1,500 W | 8 h | $61.20 |
The pattern: anything that makes heat or cold dominates. Electronics are cheap to run; resistive heating is expensive — a single space heater can out-cost every light in the house combined, many times over.
Where to Find Your Wattage and kWh Rate
Wattage: the label often shows the MAXIMUM draw, not typical use — a fridge labeled 700 W actually cycles its compressor and averages 100–200 W. For cycling appliances (fridges, AC, washers), a $15–25 plug-in kWh meter measures the truth over a day or week; for always-max devices (heaters, bulbs, kettles) the label is accurate.
Rate: divide your bill's total by its kWh to get the all-in rate — commonly 20–40% above the advertised supply rate once delivery and fees fold in. Time-of-use plans complicate it further (cheap nights, expensive late afternoons); if you're on one, run this calculator with the rate for the hours you'd actually use the appliance.