Electricity Cost Calculator
Estimate what any appliance costs to run: enter its wattage, hours per day, and your electricity rate to get cost per day, month, and year.
How this calculator works
This calculator turns an appliance’s power rating into a running cost. It first converts watts and daily hours into energy used, measured in kilowatt-hours (kWh), then multiplies that energy by your electricity rate to get the cost.
Once it has the daily cost, it scales up to a monthly and yearly figure so you can see the full picture at a glance.
Formula: Energy per day (kWh) = Watts × hours ÷ 1000; Cost = kWh × rate. Month = daily × 30, year = daily × 365.
Worked example
A 1000 W device run for 5 hours a day at a rate of $0.15/kWh:
- Energy per day: 1000 × 5 ÷ 1000 = 5 kWh/day
- Cost per day: 5 × $0.15 = $0.75/day
- Cost per month: $0.75 × 30 = $22.50/month
- Cost per year: $0.75 × 365 = $273.75/year
Reference (100-watt device at $0.15/kWh)
| Hours/day | Cost/month |
|---|---|
| 1 h | $0.45 |
| 4 h | $1.80 |
| 8 h | $3.60 |
| 24 h | $10.80 |
How to use
Enter the appliance wattage, how many hours a day you run it, and your electricity rate in dollars per kWh. The calculator returns the cost per day, month, and year. Adjust the hours or rate to compare devices or test different usage habits.
Electrical work is code-governed and safety-critical. Confirm circuit, breaker, and conductor sizing with a licensed electrician and your local code.
Frequently asked questions
How is the running cost of an appliance calculated?
First convert power to energy: multiply the wattage by hours used per day, then divide by 1000 to get kilowatt-hours (kWh). Multiply that by your electricity rate to get the daily cost. To project further, multiply the daily cost by 30 for a month and by 365 for a year.
Where do I find my electricity rate?
Your rate, in dollars per kWh, is printed on your utility bill, usually near the usage summary. Rates vary widely by region and can change by season or time of day. If you have tiered or time-of-use pricing, use your average blended rate for the closest estimate.
Why divide the wattage by 1000?
Electricity is billed in kilowatt-hours, and a kilowatt is 1000 watts. Dividing the wattage by 1000 converts watts to kilowatts before multiplying by hours. A 1000-watt device is exactly 1 kilowatt, so running it for one hour uses 1 kWh.
Does this include standby or phantom power?
No. The estimate assumes the device only draws power during the hours you enter. Many appliances also pull a small standby load when switched off but still plugged in. For an always-on device, enter 24 hours per day to capture its full daily energy use.
Estimates only. Verify quantities with your supplier before purchasing.