Watts to Cost per Hour Calculator
A 1,200-watt appliance costs $0.223 per hour to run at the US average residential rate of 18.56c/kWh. The formula is simple: watts ÷ 1,000 × rate per kWh = cost per hour.
Per hour
$0.223
Per day (3h)
$0.668
Per month
$20.04
Per year
$244
Monthly figure assumes 30 days at 3 hours/day. Continuous (24/7) running multiplies the per-hour cost by 720/month.
State rates from EIA Electric Power Monthly. US average residential rate 18.56c/kWh.
Cost per Hour by Wattage (US Average, 18.56c/kWh)
At the US average residential rate of 18.56c/kWh (March 2026). The per-hour column is the cost while the device is actually drawing that power; the per-day column assumes continuous (24-hour) running, which most appliances do not do.
| Wattage | Per hour | Per day (24h) |
|---|---|---|
| 100 W | $0.019 | $0.45 |
| 140 W | $0.026 | $0.62 |
| 145 W | $0.027 | $0.65 |
| 200 W | $0.037 | $0.89 |
| 300 W | $0.056 | $1.34 |
| 400 W | $0.074 | $1.78 |
| 500 W | $0.093 | $2.23 |
| 800 W | $0.148 | $3.56 |
| 1,000 W | $0.186 | $4.45 |
| 1,200 W | $0.223 | $5.35 |
| 1,500 W | $0.278 | $6.68 |
| 1,800 W | $0.334 | $8.02 |
| 2,000 W | $0.371 | $8.91 |
| 3,000 W | $0.557 | $13.36 |
Appliance examples are typical running wattages and vary by model. Rates refresh monthly from EIA Electric Power Monthly Table 5.6.A. For your state, use the calculator above or see rates by state.
The Formula, Step by Step
1. Watts to kilowatts
Divide the appliance wattage by 1,000. A 1,200-watt microwave is 1.2 kW. The wattage is on the nameplate or manual; if only amps are shown, watts = amps x volts (120V for standard US outlets).
2. Multiply by your rate
Multiply kilowatts by your electricity price in dollars per kWh. At the US average of 18.56c/kWh that is 0.1856 per kWh. So 1.2 kW x 0.1856 = $0.22 per hour.
3. Scale to your usage
Multiply the per-hour cost by the hours you actually use the device each day, then by 30 for a month or 365 for a year. Thermostat-controlled devices (heaters, AC, fridges) cycle on and off, so use roughly half their always-on figure.
Frequently Asked Questions
How much does 1,200 watts cost per hour?+
A 1,200-watt appliance uses 1.2 kWh every hour, so at the US average residential rate of 18.56c/kWh (March 2026, EIA Electric Power Monthly) it costs about $0.22 per hour to run. Over a full 24-hour day that is about $5.35. Your exact cost depends on your state rate, which ranges from about 11c/kWh to over 40c/kWh.
How do I calculate the cost of running an appliance per hour?+
Divide the appliance's wattage by 1,000 to get kilowatts, then multiply by your electricity rate in dollars per kWh. For example, an 1,800-watt appliance is 1.8 kW; at 18.56c/kWh that is 1.8 x 0.1856 = about $0.33 per hour. Multiply by hours used per day, then by 30 or 365, for monthly and annual cost. The wattage is printed on the appliance's nameplate or in its manual; if only amps are listed, watts = amps x volts (volts is 120 for most US household outlets).
What is the difference between watts and watt-hours on my bill?+
Watts measure power (how fast energy is drawn at any instant); watt-hours measure energy used over time. Your utility bills you per kilowatt-hour (kWh), which is 1,000 watt-hours. A 1,000-watt appliance running for one hour uses exactly 1 kWh. A 100-watt bulb running for 10 hours also uses 1 kWh. So a high-wattage device used briefly can cost less than a low-wattage device left on all day.
Does a higher-wattage appliance always cost more to run?+
Only per hour. Total cost is wattage multiplied by hours of use, so a 1,500-watt space heater used 2 hours a day costs less per month than a 145-watt mini fridge that runs 24/7. When estimating a bill, always multiply the per-hour figure by realistic daily run-time. Appliances with motors or heating elements (heaters, kettles, dryers, AC) are the high-wattage items worth focusing on; electronics on standby draw only a few watts each.
How much does it cost to run a 1,500-watt space heater all day?+
A 1,500-watt heater uses 1.5 kWh per hour, costing about $0.28 per hour at the US average of 18.56c/kWh. Running it 24 hours costs about $6.68 per day, or roughly $200 per month. In high-rate states like California or Hawaii that monthly figure can nearly double. Heaters with a thermostat cycle on and off, so real-world cost is usually 40-70% of the always-on figure.
