Electricity Cost Calculator
Cost = (watts × hours ÷ 1000) × $/kWh
How Electricity Cost Calculations Work
Electricity bills are based on kilowatt-hours (kWh) — the energy consumed when a device drawing 1,000 watts runs for one hour. The formula is: daily kWh = (watts × hours per day) ÷ 1,000. Cost = kWh × price per kWh. A 1,500-watt space heater running 8 hours daily uses (1,500 × 8) ÷ 1,000 = 12 kWh per day.
At $0.15 per kWh — close to the U.S. average — that heater costs 12 × $0.15 = $1.80 per day, $54 per month (× 30), and $657 per year (× 365). Central air at 3,500 watts for 6 summer hours daily hits 21 kWh/day, or $3.15 daily and $94.50 monthly at the same rate. Small loads add up too: a 100-watt TV for 5 hours is just 0.5 kWh ($0.075/day).
Wattage labels appear on appliance nameplates, in manuals, or in ENERGY STAR databases. Running watts differ from starting surge — refrigerators cycle on and off, so average draw is lower than peak rating. Multiply listed amps × volts (typically 120 V) when only amperage is given: 12.5 A × 120 V = 1,500 W.
Reducing runtime or upgrading efficiency pays off fastest on high-watt devices. Switching a 60-watt incandescent bulb to a 9-watt LED for 6 hours daily saves 0.306 kWh/day — about $17/year at $0.15/kWh per bulb. Smart plugs and meter readings help verify real-world draw versus nameplate specs. Seasonal rate plans and time-of-use pricing can shift costs further — run dishwashers and dryers during off-peak hours when your utility offers lower kWh rates overnight.
| Appliance | Watts | 8 hr/day @ $0.15 |
|---|---|---|
| Space heater | 1,500 W | $1.80/day |
| Central AC | 3,500 W | $4.20/day |
| Refrigerator (avg) | 150 W | $0.18/day |
| Clothes dryer | 3,000 W | $3.60/day |
Enter wattage, daily usage hours, and your utility rate to see daily, monthly, and yearly costs. Use appliance presets for common household devices or enter custom wattage for any load.
Examples
| Example | Result |
|---|---|
| Space heater 1,500 W, 8 hr/day, $0.15/kWh | $1.80/day, $54/mo |
| AC 3,500 W, 6 hr/day, $0.15/kWh | $3.15/day, $94.50/mo |
| Refrigerator 150 W, 24 hr/day, $0.12/kWh | $0.43/day, $13/mo |
| TV 100 W, 5 hr/day, $0.15/kWh | $0.075/day, $2.25/mo |
| Dryer 3,000 W, 1 hr/day, $0.15/kWh | $0.45/day, $13.50/mo |
| Microwave 1,000 W, 0.5 hr/day, $0.15/kWh | $0.075/day |
| Desktop PC 200 W, 10 hr/day, $0.15/kWh | $0.30/day, $9/mo |
Frequently asked questions
Check the nameplate, user manual, or manufacturer specs. If only amps are listed, multiply amps × 120 volts for wattage on standard U.S. circuits.
The national average is roughly $0.14–$0.17 per kWh, but rates vary by state and provider. Check your electric bill for your exact rate.
Your home runs many devices simultaneously. This calculator estimates one appliance at a time — sum multiple loads for a fuller picture.