Space Heater Running Cost Calculator
See what a space heater costs to run per hour, per day and per month from its wattage, the hours it runs and your electricity rate.
A plug-in heater has no efficiency rating to shop for: the watts on the label are the heat it makes and the bill it runs up. This prices yours by the hour, day and month from the wattage, the hours it actually runs, and your rate, and shows what it pulls from the outlet.
Heater wattage
On the label or the box. High is 1,500 W on nearly every plug-in heater, the most a standard outlet allows; low is 750–900 W. Ceramic, oil-filled and infrared all cost the same at the same watts.
How much it runs
A heater with a thermostat cycles off once the room is warm, so a heater that's "on" all evening may run half of it. Count the running hours: 4–8 for an evening in one room, 24 if it runs around the clock.
How many heaters
Each one at the wattage above. Two heaters is a bedroom and an office; keep them on different circuits.
Electricity rate
Your price per kilowatt-hour, from a recent bill. The 2026 U.S. average is about $0.18/kWh, but it ranges from about $0.11 to over $0.40 by state.
Running cost per month
$49
1,500 W × 6 hours a day = 270 kWh a month at $0.18/kWh
Why a $300 heater costs the same to run as a $30 one
Every plug-in heater turns the watts it draws straight into heat, so the manufacturers' own cost formulas are just kilowatts times your rate: high is 1.5 kW, low about 0.9. Ceramic, oil-filled, infrared and fan heaters at the same wattage cost the same per hour; what differs is how the heat is spread and how quiet it is. The levers are the low setting, which cuts the hourly cost by about 40 percent, the thermostat, which stops the element once the room is warm, and running it in the one room you're in while the rest of the house sits cooler.
One heater per outlet, straight into the wall
On high a 1,500-watt heater pulls 12.5 amps, most of the 15-amp circuit an ordinary outlet sits on, which is why a second heater, a hair dryer or a microwave on the same circuit trips the breaker. Plug it directly into the wall and never into an extension cord or power strip, which overheat under that load; put nothing else on the same outlet; keep three feet clear of bedding, curtains and furniture; and turn it off when you leave the room or sleep. Space heaters are 30 percent of home heating fires but 73 percent of the deaths.
Cost is wattage × heaters × hours running × your rate, over a 30-day month; amps are watts ÷ 120 volts. A heater with a thermostat cycles off once the room is warm, so enter the hours it actually runs, not the hours it's switched on. Rate defaults to the EIA national residential average. 2026 figures.
💡About this calculator▼
A space heater is the one appliance where shopping for efficiency is pointless. Every plug-in heater turns the watts it draws straight into heat, so a ceramic, an oil-filled radiator and an infrared panel at 1,500 watts all cost exactly the same per hour; the manufacturers' own cost answers are simply kilowatts times your rate. The bill is set by three things you control: the setting, the hours it actually runs, and how many rooms you're heating this way.
This prices yours. Enter the wattage on the label, the hours a day the element is really running, the number of heaters, and your rate from a recent bill. You get the cost per hour, per day and per 30-day month, the kilowatt-hours it adds to the bill, and the amps it pulls from the outlet.
The hours are the whole game. A heater with a thermostat cycles off once the room is warm, so one that's switched on for an evening may run half of it, while one holding a cold garage runs flat out. The difference between a $16 month and a $194 month is almost entirely hours, not the heater.
Start with the watts. Nearly every plug-in heater sold in the U.S. runs 1,500 watts on high, because that is about as much as a standard outlet can supply, and 750 to 900 watts on low. Lasko's own cost formula is 1.5 kilowatts times your rate on high and 0.9 on low; DeLonghi's is the same, with the note that the unit cycles on and off and draws nothing while it's off. There is no efficiency factor to apply, because a resistance heater's watts are its heat.
Multiply by the hours it actually runs. Cost per hour is kilowatts times heaters times your rate per kilowatt-hour. Cost per day multiplies by the running hours you enter, and cost per month multiplies by 30. The calculator asks for running hours rather than hours switched on, because a thermostat-controlled heater in a warm room may run half the time it's on, and no source publishes a duty-cycle factor honest enough to build in.
Check the outlet. Amps are watts divided by 120 volts, so a 1,500-watt heater pulls 12.5 amps of the 15-amp circuit behind an ordinary outlet. That is why the safety agencies say to plug it straight into the wall with nothing else on the outlet, and why a heater rated above about 1,800 watts is flagged: it is a 240-volt or hard-wired unit that needs its own circuit, not a plug-in.
Worked example. A 1,500-watt heater running 6 hours a day at the 2026 national average of $0.18 per kilowatt-hour: 1.5 kW × $0.18 = $0.27 an hour; × 6 hours = $1.62 a day; × 30 days = $49 a month, for 270 kilowatt-hours. Around the clock the same heater is $6.48 a day and $194 a month.
📐How it's calculated▼
Cost per hour = watts × heaters ÷ 1,000 × rate per kWh. For 1,500 W, one heater and $0.18: 1.5 × 0.18 = $0.27.
Cost per day = cost per hour × hours actually running. 6 hours: $0.27 × 6 = $1.62. Around the clock: $0.27 × 24 = $6.48.
Cost per month = cost per day × 30. $1.62 × 30 = $48.60, shown as $49. Around the clock: $194.
Electricity used = kW × hours × 30. 1.5 × 6 × 30 = 270 kWh a month.
Amps = watts ÷ 120 volts. 1,500 ÷ 120 = 12.5 amps; 750 ÷ 120 = 6.3 amps. Anything above 1,800 watts exceeds the 15-amp circuit behind a standard outlet and is flagged as needing its own circuit.
On low: 750 W for 8 hours at $0.18 is 0.75 × 0.18 = $0.14 an hour, $1.08 a day, $32 a month.
📎Sources:U.S. Energy Information Administration — Electric Power Monthly, Table 5.6.A (average residential price, cents per kWh),Lasko — How much does it cost to run a space heater? (1.5 kW high, 0.9 kW low × your rate),U.S. Consumer Product Safety Commission — Stay Warm Safely: space heater fire statistics and safety tips (Jan. 2025),National Fire Protection Association — Safety with heating equipment (2020–2024 heating fire statistics)
🔍Finding your inputs▼
Heater wattage: Printed on the label near the plug and on the box. High is 1,500 W on almost every plug-in heater; low is 750 to 900 W. If yours has three settings, use the one you actually run. Heater type does not matter at the same watts.
Hours a day it's actually running: The hours the element is on, not the hours the switch is on. A heater with a thermostat in a room that reaches temperature cycles off, so an evening switched on for 8 hours might be 4 or 5 running hours; a heater holding a cold garage or a drafty room runs nearly flat out. Enter 24 for around the clock.
How many heaters: Each one at the wattage above. Two heaters is a bedroom and an office; the month is doubled, and each should be on a different circuit.
Electricity rate: The per-kilowatt-hour price on your bill, including delivery charges. The 2026 U.S. residential average is about $0.18, but state averages run from around $0.11 to over $0.40, so your own number matters more than any input except hours.
⚠️Special situations▼
My heater has a thermostat and I leave it on all night. Do I enter 9 hours?
Enter the hours it actually runs, which is fewer. Once the room reaches the set temperature the element cycles off and draws nothing until the room cools, so a heater on for 9 hours in an insulated bedroom might run 4 to 5. If you want a ceiling, enter the full 9; the true cost sits between that and about half of it, and the better your room holds heat the closer to half it is.
Is an oil-filled radiator cheaper to run than a ceramic fan heater?
Not at the same wattage. Both turn every watt into heat, so 1,500 watts costs the same per hour whichever box it comes in. The oil-filled unit feels cheaper because it keeps radiating after the element cycles off, and it is quieter; the fan heater warms you faster. Pick on comfort and noise, and save money with the low setting and the thermostat, not the type.
The breaker trips when I run the heater and the microwave. Is the heater faulty?
Probably not. A 1,500-watt heater pulls 12.5 amps, a microwave about 10 to 12, and together they exceed the 15 amps the circuit can carry, so the breaker does its job. Move the heater to an outlet on a different circuit, and never solve it with an extension cord or power strip, which overheat under a heater load.
Is it cheaper to run a space heater than my central heat?
Only if it lets you turn the rest of the house down. Electricity is an expensive way to make heat compared with gas, so a heater running alongside the furnace at the same thermostat setting just adds this calculator's number to the bill. Heating the one room you're in while the thermostat sits several degrees lower can come out ahead; heating three rooms this way rarely does.
❓Common questions▼
How much does it cost to run a 1,500-watt space heater per hour?
About $0.27 an hour at the 2026 U.S. average of $0.18 per kilowatt-hour: 1.5 kilowatts times the rate. At $0.12 it is $0.18 an hour, at $0.32 it is $0.48. On the low setting, 750 to 900 watts, it is roughly half. The per-hour figure is the one that never depends on your habits; everything else is hours.
How much does a space heater cost to run 24/7?
A 1,500-watt heater running flat out around the clock uses 36 kilowatt-hours a day, which is $6.48 a day and $194 a month at $0.18 per kilowatt-hour, or $346 a month at a $0.32 rate. Few heaters truly run 24 hours: one with a thermostat in a room that holds heat cycles off much of the time, so the real cost is often half to two-thirds of the flat-out number.
Do space heaters use a lot of electricity?
Yes, by household standards. At 1,500 watts a space heater on high draws more than almost anything else you plug into a wall outlet, about the same as a microwave or a hair dryer, and unlike those it runs for hours. Six hours a day is 270 kilowatt-hours a month, a noticeable line on most bills; around the clock it is over 1,000. The saving grace is that it heats one room, so it can pay off if the rest of the house is turned down.
Which type of space heater is the cheapest to run?
None of them, at the same wattage. Ceramic, oil-filled, infrared, micathermic and fan-forced heaters are all electric resistance heaters, and every watt drawn becomes heat, so 1,500 watts costs the same per hour in any of them. What differs is comfort: infrared warms people and objects in front of it, an oil-filled radiator keeps giving off heat after it cycles off, a fan heater warms the air fastest. The cheap choice is the low setting plus a thermostat.
Can I run a space heater on an extension cord or power strip?
No. The Consumer Product Safety Commission and the Electrical Safety Foundation both say to plug a space heater directly into a wall outlet and never into an extension cord or power strip, which can overheat under a 12.5-amp load and start a fire, and to plug nothing else into the same outlet. Keep it three feet from bedding, curtains and furniture, and turn it off when you leave the room or go to sleep; portable heaters are involved in about 1,600 fires and 70 deaths a year.
🔗 Related Calculators
Basement Dehumidifier Running Cost
Estimate what it costs to run a basement dehumidifier — per month and per year — by unit size (pint capacity), ENERGY STAR, how damp the basement is, and your electricity rate. See why the biggest savings come from fixing the moisture, not the setpoint.
Air Purifier Running Cost
Calculate what an air purifier really costs to run — electricity by size, hours, and your kWh rate, plus the replacement filters that usually cost more than the power. ENERGY STAR savings included.
Heat Pump vs Gas Furnace Calculator
Compare a heat pump against a gas furnace for your home. See your annual heating cost each way, the payback period on the extra upfront cost, and net savings over time.