Home Power Consumption Calculator
Calculate your home electricity usage and cost.
Add appliances with their wattage and daily hours to estimate monthly kWh and electric bill.
Electricity consumption and cost are calculated using kilowatt-hours (kWh) — the standard unit on your electricity bill. One kilowatt-hour equals 1,000 watts running for 1 hour.
Core formulas:
Daily kWh = (Wattage × Hours Used per Day) / 1,000
Monthly kWh = Daily kWh × 30
Monthly Cost = Monthly kWh × Electricity Rate ($/kWh)
Annual Cost = Monthly Cost × 12
Common appliance wattages and monthly costs (at $0.16/kWh, US average):
| Appliance | Watts | Daily Hours | Monthly kWh | Monthly Cost |
|---|---|---|---|---|
| LED bulb | 10 | 6 | 1.8 | $0.29 |
| Phone charger | 5 | 3 | 0.45 | $0.07 |
| Laptop | 60 | 6 | 10.8 | $1.73 |
| Desktop + monitor | 250 | 6 | 45 | $7.20 |
| Refrigerator | 150 | 8 (see note) | 36 | $5.76 |
| 55" LED TV | 80 | 5 | 12 | $1.92 |
| Washing machine | 500 | 1 | 15 | $2.40 |
| Clothes dryer | 3,000 | 1 | 90 | $14.40 |
| Dishwasher | 1,800 | 1 | 54 | $8.64 |
| Central AC (2-ton) | 2,500 | 6 | 450 | $72.00 |
| Space heater | 1,500 | 4 | 180 | $28.80 |
| Electric water heater | 4,500 | 3 | 405 | $64.80 |
The duty cycle catch, which is where most estimates go wrong
A refrigerator is plugged in 24 hours a day, but its compressor is not running for 24 hours a day. It cycles on and off to hold temperature, typically running about a third of the time, which works out near 8 equivalent hours at full draw. Enter 150 W × 24 h and you will predict 108 kWh a month for a fridge that actually uses 35 to 45.
The same applies to anything thermostatically controlled: air conditioning, space heaters, electric water heaters, freezers. Enter the hours the compressor or element is actually running, not the hours the appliance is switched on. For an air conditioner on a hot day that might be 60 to 80% of the time it is on; on a mild day, far less.
Things that draw steadily, like lights, televisions, computers and chargers, do not have this problem. For those, hours switched on is exactly right.
US electricity rates by state range (2025): $0.10/kWh (Louisiana) to $0.35+/kWh (Hawaii, California)
Worked example: Central AC running 6 hours/day for 4 summer months at $0.22/kWh: Monthly kWh = 2,500 × 6 / 1,000 × 30 = 450 kWh 4-month cost = 450 × 4 × $0.22 = $396
Top energy-saving tips:
- Replace incandescent bulbs with LED, saves ~85% per bulb
- Unplug chargers and electronics when not in use (phantom load can be 5–10% of the bill)
- Raise the AC thermostat by 1°F, saves ~3% on cooling costs
- Switch to cold-water laundry, 90% of washing machine energy heats the water
- Air-dry dishes instead of using the dishwasher’s heated dry cycle
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.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.