Space heaters use more electricity per hour than most household appliances, but less than you might think

A typical space heater draws between 750 and 1,500 watts when running. To put that in perspective: a microwave uses about 1,000 watts, a hair dryer uses 1,500 watts, and a refrigerator uses 150 to 800 watts depending on the model. The difference is that you run a microwave for minutes, a hair dryer for maybe ten minutes, and a refrigerator continuously. A space heater often runs for hours at a time, which is why the electricity bill impact feels larger than the wattage alone suggests.

Whether a space heater "uses a lot" depends on your local electricity rate and how long it runs. At the U.S. average rate of roughly 14 cents per kilowatt-hour, running a 1,500-watt heater for eight hours costs about $1.68. Running it for four hours costs about 84 cents. If you run it every day for a month, that is roughly $50 to $100 added to your bill, depending on the wattage and how many hours per day. In states with higher rates — California, Massachusetts, Hawaii — the cost is noticeably higher. In states with lower rates, it is lower.

Key Takeaways

  • Space heaters draw 750 to 1,500 watts, which is high per hour but comparable to other common appliances like hair dryers and microwaves.
  • The total cost depends on how many hours per day you run it and your local electricity rate, which varies significantly by state and utility.
  • Running a 1,500-watt heater eight hours daily for a month typically adds $50 to $100 to your electricity bill at average U.S. rates.
  • Using a space heater to warm one room instead of heating your whole house can reduce overall energy use, but only if you lower your central thermostat.

Why space heater wattage matters more than the number itself

The wattage rating tells you the maximum power draw, but the actual electricity used depends on whether the heater runs continuously or cycles on and off. Most space heaters have a thermostat that turns the heating element on when the room temperature drops below the set point and off when it reaches the target. A heater set to 72 degrees in a well-insulated room might cycle on for 15 minutes, then off for 30 minutes. The same heater in a drafty room or set to 78 degrees might run almost constantly.

The type of heater also matters. Ceramic heaters and oil-filled radiators are more efficient at converting electricity to heat than older coil heaters, but they all use roughly the same wattage when running. Infrared heaters focus heat on objects and people rather than warming the entire air, which can feel warmer at a lower wattage, but the electricity draw is still high while the unit is on.

How to calculate your actual cost

To estimate what a space heater will add to your bill, you need three numbers: the wattage (usually printed on the back or in the manual), the number of hours you run it per day, and your electricity rate per kilowatt-hour. Your utility bill shows the rate — look for a line that says "per kWh" or similar. If you cannot find it, call your utility or check their website.

The formula is: (Wattage ÷ 1,000) × Hours per day × Days per month × Rate per kWh = Monthly cost. For example, a 1,200-watt heater running six hours daily for 30 days at 14 cents per kilowatt-hour costs (1.2 × 6 × 30 × 0.14) = $30.24 per month. If your rate is 20 cents per kilowatt-hour, the same heater costs $42.40 per month.

When a space heater actually saves money on heating

A space heater saves money only if you lower your central heating thermostat while using it. If you heat the whole house to 72 degrees and then add a space heater to one room while keeping the central heat at 72, you are heating twice and using more electricity overall. The savings come from heating one room to 72 while the rest of the house stays at 65 or 60 degrees.

The break-even point depends on your home's size, insulation, and how much lower you set the central thermostat. In a small apartment, lowering the main heat by 5 degrees while running a space heater in one room might save money. In a large house with poor insulation, the central heating system might be more efficient because it distributes heat more evenly. The only way to know is to compare your bill before and after using the space heater with the central thermostat lowered.

How space heater electricity use compares to central heating

Central heating systems vary widely in efficiency, but most modern furnaces and heat pumps convert 80 to 98 percent of energy into heat. Space heaters convert nearly 100 percent of electricity into heat, but they do it in a small area. The real difference is distribution: a furnace heats the whole house with one system, while a space heater heats one room and wastes energy heating the rest of the house if the central system is still running.

If you have an older furnace (built before 1990), it may be only 60 to 70 percent efficient, which means a space heater could be more efficient for heating a single room. If you have a modern heat pump or a furnace installed in the last 15 years, the central system is likely more efficient overall, even if you are only using one room. The exception is if you can completely turn off the central heating and rely only on the space heater — then the space heater is almost certainly cheaper, but this only works in mild climates or for short periods.

Safety and electricity limits you should know

Space heaters draw enough current that plugging one into an outlet shared with other high-power devices can trip a circuit breaker. Most household circuits are 15 or 20 amps. A 1,500-watt heater draws about 12.5 amps on a 120-volt circuit, leaving little room for anything else on that circuit. Plugging a space heater into the same outlet as a microwave, toaster, or another heater can overload the circuit and shut off power to that outlet or the whole room.

Always plug a space heater directly into a wall outlet, not into a power strip or extension cord. Power strips and cords are not rated for the sustained current a space heater draws, and they can overheat and cause a fire. If your outlet is far from where you need the heater, have an electrician install a new outlet rather than using an extension cord.

Frequently Asked Questions

Does a space heater use more electricity than leaving my central heat on?

Only if you lower your central thermostat while using the space heater. If you run both at full capacity, you are using more electricity overall. The savings come from heating one room to comfort temperature while keeping the rest of the house cooler.

What is the cheapest type of space heater to run?

All space heaters use roughly the same amount of electricity when running at the same wattage. Ceramic and oil-filled heaters feel more efficient because they distribute heat more evenly, but they draw the same watts as coil heaters. The cheapest option is the lowest wattage that keeps you warm — a 750-watt heater costs half as much to run as a 1,500-watt heater.

Can I run a space heater on a 15-amp circuit with other appliances?

No. A 1,500-watt heater draws about 12.5 amps, leaving only 2.5 amps for anything else on that circuit. Plugging in a lamp or phone charger might be fine, but a microwave, toaster, or second heater will trip the breaker. Plug the space heater into its own dedicated outlet.

How much does it cost to run a space heater all night?

At average U.S. rates, running a 1,500-watt heater for eight hours costs about $1.68. A 1,200-watt heater costs about $1.34. The exact cost depends on your local electricity rate — check your utility bill for the per-kilowatt-hour price.

Will a space heater increase my electric bill noticeably?

Yes, if you run it regularly. Running a 1,500-watt heater four hours daily for a month adds roughly $50 to your bill at average rates. If you run it eight hours daily, expect roughly $100 added per month. The impact is smaller in states with lower electricity rates and larger in states like California or Massachusetts.