Electricity Cost Calculator
Enter an appliance's wattage, how long you run it, and your electricity rate to calculate the cost.
Last updated: September 5, 2026
Frequently asked questions
How much does it cost to run a 100W device for 5 hours a day?
At a typical rate of $0.15/kWh: about $0.075 per day, or roughly $2.25 over 30 days - 100W × 5 hours = 0.5 kWh per day, times $0.15.
How do I convert watts to kilowatt-hours?
Kilowatt-hours = watts ÷ 1000 × hours of use. A 1000-watt device running for 1 hour uses exactly 1 kWh - it's a measure of total energy consumed, not just power draw.
Where do I find my electricity rate?
Check your utility bill - it's usually listed as a price per kilowatt-hour (kWh), though many utilities use tiered or time-of-use rates that vary depending on how much you use or when, which this simple calculator doesn't account for.
Why does my calculated cost differ from my actual bill?
Real bills often include additional fixed charges, taxes, and tiered or time-of-use pricing that a simple flat-rate calculation doesn't capture - this tool gives a good estimate for a single device's marginal cost, not a full bill prediction.
How much does it cost to run a 1500W space heater for 8 hours a day?
At $0.15/kWh: about $1.80 per day, or roughly $54 over 30 days - 1500W × 8 hours = 12 kWh per day, times $0.15.
Does standby power (phantom load) get included in this calculation?
No - this calculator assumes the device only draws power during the hours you specify. Many electronics continue drawing a small amount of standby power even when 'off,' which this tool doesn't account for unless you add that time separately.
Is 'kWh cost calculator' the same thing as this electricity cost calculator?
Yes - both describe converting an appliance's power draw and usage time into a dollar cost based on your electricity rate, which is exactly what this tool calculates.