Running a space heater costs a predictable amount once you convert its wattage into kilowatt-hours and multiply by your utility rate. A 1500 W heater draws 1.5 kWh per hour at full output. At the U.S. residential average of 17.30 cents per kWh, that is about $0.26 per hour. Run it 8 hours a day for 30 days and the bill comes to roughly $62. The math is straightforward, but the real number you pay depends on duty cycle, thermostat settings, room size, and whether you use the heater as primary heat or as a supplement.

Converting Wattage to Kilowatt-Hours

The first step is always the same: divide the nameplate wattage by 1,000 to get kilowatts. A 750 W heater draws 0.75 kW; a 1500 W heater draws 1.5 kW; a 2000 W heater draws 2.0 kW. Multiply that figure by the hours of operation to get kWh consumed. For example, a 1500 W heater running 5 hours uses 7.5 kWh. Multiply by your rate, and you have the direct cost.

This calculation gives the worst-case cost, because it assumes the heating element is energized the entire time. Many heaters have thermostats that cycle the element on and off to hold a set temperature. The duty cycle is the fraction of time the heater actually draws power. A heater with a 50% duty cycle running for 5 clock hours uses about 3.75 kWh, not 7.5 kWh.

Duty cycle varies widely with insulation, outdoor temperature, setpoint, and room size. A small heater in a well-insulated room may cycle at 30% or less. A heater struggling to warm a drafty space can run near 100%. Without a watt meter, assume a 60–80% duty cycle for a thermostatically controlled heater in normal winter conditions, and adjust after observing how often the element switches on and off.

Typical Hourly, Daily, and Monthly Costs

Using a winter average of 17.72 cents per kWh, a 1500 W heater at full draw costs $0.266 per hour. At a preliminary 2025 U.S. residential average of 17.30 cents per kWh, the same heater costs $0.26 per hour. These figures are close, so either rate works for planning purposes.

Daily cost depends on runtime. Eight hours at full draw is 12 kWh, or about $2.13 at 17.72 cents. A 30-day month of that usage is 360 kWh, or about $64. At a 70% duty cycle, the same 8-hour day uses 8.4 kWh, costing about $1.49 per day and $44.70 per month. The difference between full-draw and realistic cycling is large enough to change your heating strategy.

Smaller heaters cost proportionally less. A 750 W heater at full draw costs $0.133 per hour, or $1.06 for 8 hours. A 2000 W heater costs $0.354 per hour and $2.84 for 8 hours. Wattage is the single largest driver of hourly cost, so choosing a heater sized to the room matters more than picking a brand or model.

Season Hours and Total Seasonal Cost

Season cost requires an estimate of heating days and daily hours. A common approach is to multiply the number of days you expect to use the heater by the average daily runtime. For example, 120 heating days at 6 hours per day is 720 hours. A 1500 W heater at full draw would use 1,080 kWh, costing about $191 at 17.72 cents per kWh. At a 70% duty cycle, the same season uses 756 kWh and costs about $134.

Adjust the daily hours for weekends, work schedules, and occupancy. A heater used only in the evening for 4 hours has a much lower season cost than one running all day. If you use zone heating to warm only one room, this approach can save more than 20% compared with heating the whole house. The savings come from not running the central furnace for unoccupied rooms.

Setback strategies also reduce season cost. Lowering the thermostat by 7–10 degrees Fahrenheit for 8 hours a day can save up to 10% annually on heating energy. For a space heater, this means turning the unit down or off when you leave the room or sleep. The savings are proportional to the hours of setback, so a consistent routine matters more than the heater's efficiency rating.

Duty Cycle and Standby Power

All resistive electric heaters are 100% efficient at converting electricity to heat at the appliance level. No model is meaningfully better than another in terms of kWh per BTU delivered. The differences in cost come from how you use the heater, not from the heater itself. Thermostatically controlled units cycle, so nameplate wattage overstates real draw. Variable-speed or cycling appliances can run 20–40% below the worst-case figure.

Standby power adds a small but measurable load. Electronics and appliances with clocks, displays, or remote receivers draw power even when off. This can account for 5–10% of residential electricity use. For a space heater, standby power is usually negligible when the unit is unplugged, but if the heater has a digital display or timer, unplugging it during summer months avoids that small drain.

To measure your actual duty cycle, use a plug-in watt meter. Run the heater for a full cycle and note the percentage of time the element is energized. Multiply that percentage by the nameplate wattage to get average draw. Then multiply by hours of operation and your rate. This method removes guesswork and gives a cost estimate specific to your room and climate.

Heat Pumps Versus Resistance Heat

Where a heat pump is installed, a space heater costs more for the same warmth. Heat pumps move heat rather than generate it, and they cut electricity use by about 50% compared with resistance heat. A 1500 W resistance heater produces 5,120 BTU per hour at full draw. A heat pump using 1.5 kW can deliver roughly twice that amount of heat, depending on outdoor temperature and the unit's coefficient of performance.

This comparison matters when deciding whether to run a space heater or the heat pump. If the heat pump is functional and the outdoor temperature is within its operating range, the heat pump is almost always cheaper per BTU. A space heater makes economic sense when you want to heat only one small room and the central system would otherwise heat the whole house. In that scenario, zone heating with a space heater can be less expensive than raising the thermostat for the entire home.

Insulation changes the calculation. A poorly insulated room loses heat quickly, forcing the heater to run longer and cycle less. Improving insulation reduces duty cycle and lowers season cost. For a room that is consistently cold, check windows, doors, and wall gaps before assuming a larger heater is the answer.

Checklist for Estimating Your Cost

To build your own estimate, gather four numbers: heater wattage, your electricity rate in cents per kWh, average daily runtime in hours, and heating days per season. Divide wattage by 1,000, multiply by daily hours, multiply by heating days, then multiply by the rate. This gives the full-draw season cost.

Apply a duty cycle factor if the heater is thermostatically controlled. Start with 0.7 as a reasonable default, then adjust up for cold rooms and down for mild climates or well-insulated spaces. Multiply the full-draw cost by this factor to get a realistic estimate. If you have a watt meter, measure the duty cycle directly and use that number instead.

Compare the result with your central heating cost. If the space heater runs 6 hours per day for 120 days at 1500 W and 70% duty cycle, the season cost is about $134. That may be less than the marginal cost of heating the whole house for the same period. If a heat pump is available, check its operating cost for the same hours. The heat pump will likely win on cost, but the space heater may still be cheaper for occasional single-room use.