Monthly cost = wattage x hours x rate / 1000. A 1,500W heater for 8 hours daily costs ~ at/kWh.
- Heater type doesn't change efficiency; wattage and runtime drive costs. Use thermostats and timers to save.
- Compare space heater costs with central heating based on your local fuel prices and usage patterns.
How to Calculate Monthly Space Heater Costs
Start with the heater's wattage, usually printed on the label. Most portable units use 1,500 watts on high. Multiply wattage by hours used per day to get watt-hours. Divide by 1,000 to convert to kilowatt-hours (kWh). Then multiply by your electricity rate per kWh. For example, 1,500 watts for 8 hours equals 12 kWh daily. At per kWh, that's per day, or for a 30-day month. Check your utility bill for the exact rate, which averages per kWh in the U.S. as of 2025.
Comparing Heater Types: Which Is Cheapest to Run?
Ceramic, infrared, oil-filled, and fan-forced heaters all have different efficiencies. Most electric space heaters are 100% efficient at converting electricity to heat, so wattage is the main cost driver. A 1,500-watt heater costs the same to run regardless of type. However, oil-filled radiators retain heat longer, allowing shorter runtimes. Infrared heaters warm objects directly, which may feel warmer at lower settings. Fan-forced heaters heat a room quickly but cool down fast. Choose based on room size and heating needs, not just upfront price.
Monthly Cost Estimates for Common Scenarios
A 1,500-watt heater used 8 hours daily at/kWh costs about per month. At/kWh, the same usage costs If you run it 24/7, costs quadruple to and respectively. A 750-watt heater on low uses half the electricity, so monthly costs drop to at/kWh. Using a heater only 4 hours per day cuts costs to for a 1,500W unit. These estimates assume continuous operation; thermostats reduce runtime by 20-30% in well-insulated rooms.
How to Reduce Space Heater Running Costs
Use a programmable timer or smart plug to limit runtimes. Set the thermostat to a comfortable but lower temperature, like 68°F instead of 72°F. Insulate the room by sealing drafts around windows and doors. Use the heater's thermostat, not just the high setting, to maintain temperature. Place the heater in the room you occupy, not empty spaces. Consider a heater with a built-in thermostat that shuts off when the room reaches the set point. This can cut energy use by 20% or more.
Is a Space Heater Worth the Cost Compared to Central Heating?
Space heaters can be cost-effective for heating a single room for a few hours. Central heating warms the whole house, which is wasteful if you only need one room. However, central heating often uses natural gas, which is cheaper per BTU than electricity. In many areas, gas is less expensive than electric resistance heat. Compare your utility rates: if electricity is/kWh and gas is per therm, gas may be cheaper. Use a BTU calculator to compare costs.