Electricity cost calculator

How electricity cost is worked out

Your utility bills you for kilowatt-hours (kWh). One kWh is 1,000 watts running for one hour, so a 1,500 W heater uses 1.5 kWh every hour it runs and a 10 W LED bulb takes 100 hours to use one.

At the U.S. average of 18.19¢, a 1,500 W space heater running 8 hours costs 1.5 × 8 × $0.1819 = $2.18 a day, or about $66.39 a month. The calculator does the same sum for every appliance on your list and adds them up.

Which rate to use

The number printed as the “energy charge” on a bill is often not your real rate, because delivery, transmission and riders are charged per kWh on separate lines. The honest figure is:

If you do not have a bill to hand, use your state’s average from the list. EIA works these out as residential revenue divided by kWh sold, so they already include delivery charges and fees. They are averages across every utility in the state, so yours may be a few cents either side. Time-of-use and tiered plans charge more at some hours or above some usage; use the rate for when the appliance actually runs.

Thermostats and cycling: why hours matter more than watts

The watts on a label are what an appliance draws while it is working flat out. Anything with a thermostat or a compressor spends part of its time switched off:

• Space heaters run at full power until the room reaches the set temperature, then cycle. In a cold, draughty room a 1,500 W heater may run almost all the time; in a well-insulated room, half the time or less.
• Fridges and freezers run their compressor roughly a third of the day, which is why the preset uses 8 hours, not 24. That gives about 440 kWh a year, in line with a typical modern fridge.
• Water heaters and AC are the same: count the hours the element or compressor is on, not the hours the house is occupied.

If you want an exact figure, a plug-in power meter costs about $20 and records the kWh an appliance really uses over a week.

Space heaters: what they really cost

Almost every plug-in space heater is 1,500 W on high, because that is the most a standard 15 A, 120 V outlet can safely carry continuously. That means every 1,500 W heater costs the same to run per hour, whatever the box says: oil-filled, ceramic, infrared or “eco”. All electric resistance heaters turn 100% of their power into heat, so the only ways to spend less are to run it fewer hours, on a lower setting, or in a smaller, better-sealed room.

At the U.S. average a 1,500 W heater costs $0.27 an hour, about $66.39 a month at 8 hours a day and $199 a month left on 24/7. In Hawaii, where power costs 46.28¢, the same 8 hours a day comes to $169 a month; in North Dakota at 12.36¢ it is $45.11. A heat pump delivers two to three times as much heat per kWh, which is why heating a whole house on space heaters gets expensive fast.

Average electricity rates by state

Residential average price, January to July 2026, with what a 1,500 W heater costs at 8 hours a day and what 1,000 kWh costs. The last column is the change from the same months of 2025. U.S. average: 18.19¢, up 7% on a year earlier.

Source: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.B (preliminary). These figures are averages and do not include any state or local taxes your utility adds on top.