Estimate the monthly and yearly running cost of any appliance based on its wattage, daily usage, and your electricity rate.
Enter the power rating of an appliance in watts (usually printed on a label or in the manual), how many hours a day you use it, how many days a month, and your electricity rate per kilowatt-hour from your utility bill. Click "Calculate Bill" for your estimated cost.
Energy used (kWh) = (watts × hours per day × days per month) ÷ 1000. Estimated cost = energy used × rate per kWh. Yearly cost is the monthly estimate × 12.
A 1,500-watt space heater run 3 hours a day for 30 days uses about 135 kWh a month. At a rate of $0.15 per kWh, that comes to roughly $20.25 per month, or about $243 per year if used year-round.
Where do I find my electricity rate? Check your latest utility bill for the rate per kWh, often listed as "energy charge" or "supply rate"; rates can also vary by season or time of day.
How do I find an appliance's wattage? Look for a label on the appliance itself, its manual, or its box; if only amps and volts are listed, multiply them together to estimate watts.
It sums the kWh usage of each appliance/device (wattage × hours used, converted to kWh), then multiplies total kWh by your utility's rate per kWh.
Check a recent utility bill, which usually lists your rate per kWh, or your utility provider's website for current rate schedules.
Only if you add them separately — many utility bills include a fixed monthly service charge on top of usage-based charges.