Space Heater Cost Calculator
Work out what an electric space heater costs per hour, day, week, month and heating season from its wattage, hours of use and your electricity rate — with several heaters, thermostat cycling and a cost comparison against a gas furnace or heat pump.
How it works
Cost per hour = watts ÷ 1,000 × heaters × on-time share × rate per kWh · Cost per day = cost per hour × hours per day · Monthly = daily × days · Season = monthly × months · Heat output (BTU/h) = watts × 3.412 · Same heat from gas = kWh × 3,412 ÷ 100,000 ÷ AFUE × price per therm · From a heat pump = kWh ÷ COP × rate
An electric space heater turns essentially all the electricity it uses into heat, so a 1500 W heater draws a full 1.5 kW whenever its element is on. The only ways to cut the cost are fewer hours, a lower setting or a thermostat that switches it off once the room is warm. Enter the wattage from the label, the hours a day it runs and the total per-kWh rate from your bill. The calculator gives the cost per hour, day, week, month and whole heating season, the energy used and the heat output in BTU/h. Under More options you can add several heaters, set the share of the time the heater is actually on (a thermostat-controlled heater is often on 40–70% of the time), and change the length of your heating season. Turn on the comparison to see what the same amount of heat would cost from a gas furnace (price per therm and AFUE) or a heat pump (seasonal COP). Gas or a heat pump is usually cheaper per unit of heat. A space heater can still save money when it lets you turn the central system down and heat only the room you are in.
Worked example
A 1500 W heater is 1.5 kW. At $0.17/kWh it costs 1.5 × 0.17 = $0.255 an hour. Run 8 hours a day that is 12 kWh and $2.04 daily, and over 30 days 360 kWh and about $61.20 a month. Over a five-month heating season that is $306. If a thermostat keeps it on only 60% of the time, the monthly cost falls to $36.72. The same 360 kWh of heat is about 12.3 therms. From a 90% gas furnace at $1.50 a therm that costs about $20.47, and from a heat pump with a COP of 3 it costs $20.40.
Sources: U.S. Department of Energy — Portable heaters · U.S. EIA — Energy conversion (BTU per kWh and therm)
Frequently asked questions
How much does a 1500 W space heater cost to run?
Multiply 1.5 kW by your electricity rate. At $0.17 per kWh that is about $0.26 an hour, $2.04 for 8 hours, and roughly $61 a month at 8 hours a day. At $0.30 per kWh the same use costs about $108 a month.
Are 1500 W heaters more expensive to run than 750 W?
At the same rate a 1500 W heater costs exactly twice as much per hour as a 750 W one, because cost scales with wattage. The higher setting heats a room faster, but on a thermostat both cycle off once warm, so total cost depends mostly on how long the heater actually runs. The table of heater sizes shows both side by side.
Does a thermostat lower the running cost?
Yes. A heater with a thermostat stops drawing power once the room reaches the set temperature and only switches on to top it up. In a reasonably insulated room it may be on half the time or less. Set the on-time share under More options to see the effect.
Is a space heater cheaper than central heating?
Per unit of heat, usually not: gas furnaces and especially heat pumps deliver heat more cheaply than resistance heaters. Turn on the comparison to see the numbers for your prices. A space heater wins when it lets you keep the rest of the home cooler and heat only the room you are using.
Do "energy-saving" space heaters use less power?
All resistance heaters — fan, ceramic, oil-filled, infrared — are 100% efficient at turning electricity into heat, so none is cheaper per unit of heat. Savings come from thermostats, timers and lower wattage that reduce run-time, not from the heating element itself.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.