Electricity Cost Calculator
Enter any wattage, how many hours per day it runs, and your state's electricity rate. Get the exact cost per hour, day, month, and year.
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How This Calculator Works
The formula is simple: watts × hours × (rate per kWh / 1,000) = cost.
A kilowatt-hour (kWh) is the standard unit your utility uses to measure electricity consumption. One kWh is 1,000 watts running for one hour. If your space heater uses 1,500 watts and runs for 8 hours, that is 12 kWh. Multiply by your rate per kWh to get the cost.
The rates shown here are average residential rates from the U.S. Energy Information Administration. Your actual rate may be higher or lower depending on your utility and plan. For the most accurate result, check your electricity bill for your exact per-kWh rate and enter it manually.
Where to Find Your Wattage
Most appliances list their wattage on a label or plate, usually on the back or bottom of the unit. If the label shows amps and volts instead, multiply them together: amps × volts = watts. For standard U.S. outlets, voltage is 120V. For large appliances on a 240V circuit (dryers, water heaters, EV chargers), use 240V.
If you cannot find the label, check the owner's manual or the manufacturer's website. You can also use a plug-in energy monitor (like a Kill A Watt meter) to measure actual consumption.
Where to Find Your Electricity Rate
Your electricity rate is listed on your monthly utility bill, typically shown as "price per kWh" or "energy charge." In the U.S., the average residential rate is about 16.72 cents per kWh, but rates vary dramatically by state, from around 10.76 cents in Washington to over 43 cents in Hawaii.
Quick Tip: Use Your Actual Bill Rate
- The state averages in our dropdown are a good starting point, but your utility's rate may differ.
- Some utilities use tiered pricing, where the rate increases as you use more electricity.
- Time-of-use plans charge more during peak hours and less at night.
- For the most accurate estimate, divide your total electricity charges by total kWh used on your latest bill.
Frequently Asked Questions
A kilowatt-hour is the amount of energy used by a 1,000-watt appliance running for one hour. It is the standard billing unit on your electricity bill. For example, a 100-watt light bulb running for 10 hours uses 1 kWh (100W × 10 hours / 1,000 = 1 kWh).
Several factors can cause differences. Your utility may charge tiered rates that increase with usage, add demand charges, or apply time-of-use pricing. Taxes, fees, and fixed service charges also add to your bill beyond the raw per-kWh energy cost. This calculator estimates the energy cost only, not the full bill.
Check the label on the back or bottom of the appliance, the owner's manual, or the manufacturer's website. If the label shows amps instead of watts, multiply amps by your outlet's voltage (120V for standard outlets, 240V for large appliances). For the most precise measurement, use a plug-in energy monitor.
This calculator estimates cost based on the wattage you enter, which should be the active draw during use. Many appliances also consume a small amount of power when turned off but still plugged in (standby or vampire power). Typical standby draw is 1-10 watts. To estimate standby cost, enter the standby wattage with 24 hours per day.
This calculator provides estimates for informational purposes only. Actual costs depend on your specific electricity rate, appliance condition, usage patterns, and utility fee structure. See our full disclaimer.