ReckonBoxWhat an appliance actually costs to run
The cost to run an appliance is its power in kilowatts times the hours you use it times your rate per kilowatt-hour. Wattage on the label, hours from your habits, rate off your bill, and the dollars fall out.
Take a 1,500 watt space heater run 5 hours a day. That is 7.5 kilowatt-hours daily, since 1,500 watts times 5 hours is 7,500 watt-hours, and a kilowatt-hour is 1,000 of those. At the 2025 US residential average of 17.3 cents, the heater costs about $1.30 a day, $38.92 a month, and $473.59 a year. The yearly figure is the one that surprises people, because a dollar a day never feels like much until it is a season long.
The kilowatt-hour is the unit that matters
A kilowatt-hour is the energy of running 1,000 watts for one hour, and it is the unit your electric bill charges for. Everything on the bill traces back to it.
A 100 watt bulb burning for 10 hours uses exactly 1 kilowatt-hour. The heater above uses 1.5 kilowatt-hours every single hour it runs, which is why heating dominates a winter bill. Once you can turn any appliance into kilowatt-hours per day, its watts times hours over 1,000, the rest is just multiplying by what you pay.
| 1,500 W heater, 5 hrs/day, 17.3 cents | Cost |
|---|---|
| Per day | $1.30 |
| Per month | $38.92 |
| Per year | $473.59 |
Your rate, not a stale one
The US residential average was 17.3 cents per kilowatt-hour for 2025 and had climbed to 18.83 cents by April 2026, according to the U.S. Energy Information Administration. This tool defaults to the 17.3 cent figure, but rates swing hard by state and by the time of day on some plans, so the number printed on your own bill is the one to enter. Plug in your real rate and the annual cost stops being a national average and becomes yours.
Where the numbers come from
Daily energy is watts times daily hours divided by 1,000. Daily cost is that energy times your rate. Monthly multiplies the day by 30 and yearly by 365, so a device you run every day shows its true annual weight. If you have several of the same unit, the count scales the energy directly, since two identical heaters draw twice the power for the same hours.
What this does not cover
This prices a device at the wattage and hours you enter. It does not track standby draw, the few watts many electronics pull while off, which is small per device but real across a whole house. For something that cycles rather than runs steadily, like a refrigerator or an air conditioner, use its average hours of actual running, or read the labeled annual kilowatt-hours off the yellow EnergyGuide sticker and divide by 365 for a daily figure. Steady loads are easy; cycling ones need that adjustment.
Add up the three or four things you leave running longest, and the bill usually stops being a mystery.
Frequently asked questions
How do I calculate the cost to run an appliance? Multiply the wattage by the hours used, divide by 1,000 for kilowatt-hours, then multiply by your rate per kWh. A 1,500 watt space heater run 5 hours a day uses 7.5 kWh, which at the 2025 US average of 17.3 cents is about $1.30 a day, $38.92 a month, and $473.59 a year. Your own rate makes it exact.
What is a kilowatt-hour? A kilowatt-hour is the energy of running 1,000 watts for one hour, and it is the unit your electric bill charges for. A 100 watt bulb left on for 10 hours uses 1 kWh. So a device kWh per day is its watts times daily hours divided by 1,000, and multiplying by your rate turns energy into dollars.
What is the average electricity rate in the US? The US residential average was 17.3 cents per kilowatt-hour for 2025 and had risen to 18.83 cents by April 2026, per the U.S. Energy Information Administration. Rates vary widely by state and by time of day on some plans, so the figure on your own bill is the one to enter for an accurate result.
Why is my space heater so expensive to run? Because resistance heating draws a lot of power for long stretches. At 1,500 watts, a heater uses 1.5 kWh every hour, so running it 5 hours a day is 7.5 kWh, more than many homes use for everything else in a morning. Over a winter that adds up, which is why heating is often the largest line on a cold-month bill.
Does this include standby or phantom power? No, this calculates the cost while the device draws the wattage you enter for the hours you set. Many electronics also pull a few watts on standby, which adds up across a house but is not modeled here. For a device that cycles, like a fridge, use its average daily hours of actual running rather than 24, or its labeled annual kWh.