Electricity Cost Calculator
What an appliance costs to run per day, month, and year.
Input sheet
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That always-on space heater or gaming PC quietly adds up on your power bill. This calculator turns an appliance's wattage and daily run time into what it actually costs you per day, month, and year.
How it works
Watts ÷ 1000 × hours gives daily kWh; times your rate gives daily cost, scaled to month and year.
Power in watts divided by 1,000 converts to kilowatts; multiplied by hours of use it gives the kilowatt-hours (kWh) consumed each day. Multiplying kWh by your electric rate gives the daily cost, which scales to a month (×30) and year (×365).
Find an appliance's wattage on its label or nameplate; for devices that cycle on and off, like a refrigerator, use average daily run hours rather than the full 24, since the compressor only runs part of the time.
Daily cost = (watts ÷ 1000) × hours per day × rate ($/kWh); monthly = daily × 30; yearly = daily × 365.
Worked examples
A 1500 W space heater run 3 hours a day at $0.15/kWh. → $0.68 per day, about $20.25 per month and $246.38 per year.
1500 ÷ 1000 × 3 = 4.5 kWh/day; 4.5 × 0.15 = 0.675/day.
A 100 W lightbulb left on 6 hours a day at $0.15/kWh. → About $0.09 per day, roughly $32.85 per year.
0.1 kW × 6 h = 0.6 kWh; 0.6 × 0.15 = 0.09/day; × 365 = 32.85.
Tips & gotchas
- Check your utility bill for your real $/kWh rate — it varies widely by region and time of day, and many plans charge more during peak hours.
- High-wattage heating appliances (space heaters, dryers, water heaters) dominate bills far more than electronics.
- A plug-in energy meter gives you the true average watts for cycling devices, which is more accurate than the nameplate maximum.
- Phantom loads from idle electronics are small per device but add up across a whole house — switch off power strips to trim them.
FAQ
Where do I find an appliance's wattage?
Look on the nameplate label, usually on the back or bottom. If only amps and volts are listed, multiply them (watts = volts × amps).
Why is my real bill higher than this estimate?
Bills include fixed connection fees, taxes, delivery charges, and tiered or peak rates. This figure covers just the energy used by that appliance.
Does a device on standby still cost money?
Yes. Many electronics draw a few watts in standby. Enter that standby wattage over 24 hours to see the small but constant cost.
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