How Much Does a Space Heater Cost to Run? Per Hour, Day and Month

A 1,500-watt space heater uses 1.5 kilowatt-hours of electricity for every hour at full power. At 18 cents per kWh, a rough U.S. average, that costs about 27 cents an hour, around $2.16 for an 8-hour day and roughly $65 for a month of 8-hour days. Your own cost depends on your electricity rate, the wattage and how long the heater really runs.

When it gets cold, a small heater under the desk looks like a cheap way to stay warm. Sometimes it is. Sometimes it is the reason the next bill is a shock. The difference comes down to a simple calculation, which this guide shows step by step, with examples you can adjust for your own rate.

The formula

The Department of Energy teaches the same method for any appliance:

Watts × hours ÷ 1,000 = kWh. Then kWh × price per kWh = cost.

Take the most common size of space heater, rated at 1,500 watts:

• 1,500 × 1 hour ÷ 1,000 = 1.5 kWh
• 1.5 kWh × $0.18 = $0.27 an hour at full power

That figure holds for almost every 1,500-watt electric heater, whether it is ceramic, oil-filled, infrared or a fan heater. The label on the heater shows its watts. The maximum for a plug-in heater on a normal U.S. outlet is 1,500 watts, which is why you see that number everywhere.

Cost by wattage and time

Here is what different settings cost at 18 cents per kWh if the heater really ran continuously:

These are maximums. A heater with a thermostat switches itself off when the room reaches the temperature you set, so the real running time is often shorter. In a small, well-closed room the heater may be on only half the time. In a drafty room it may be on almost constantly.

What if your rate is higher or lower?

The same 1,500-watt heater costs different amounts in different places, because the price per kWh varies. This table shows the cost per hour at full power:

If you pay different rates at different times of day, use the rate for the hours you actually run the heater. A heater that runs overnight on a cheaper plan costs less than one that runs during an expensive evening peak.

Is a space heater cheaper than central heating?

It depends on what you are comparing, and how you use it.

It can save money if you:

• Turn the main thermostat down several degrees and heat only the room where you sit or sleep.
• Use it in a small room with the door closed for a short time.
• Have a house with a very expensive heating system and a very small space to warm.

It usually costs more if you:

• Use it to warm a large or open space, or a room with poor insulation.
• Run several heaters at once.
• Keep the main heating on at the same time.

The Department of Energy's page on portable heaters says they are best for heating small areas for limited periods, and not for whole-house heating. Electric resistance heat also tends to cost more per unit of heat than heat from a natural gas furnace, so a space heater is rarely cheaper than gas central heating for the same warmth. If your furnace is the problem, see when the furnace blows only cold air before you spend your winter on space heaters.

Do some heaters use less electricity than others?

This is one of the biggest myths about space heaters. Almost every watt of electricity a heater uses ends up as heat in the room. That means:

• A 1,500-watt ceramic heater and a 1,500-watt oil-filled heater use the same amount of electricity per hour.
• "Eco" modes, "energy saving" labels and fancy designs do not make the heater use less electricity for the same heat.
• A low wattage heater uses less electricity per hour, but gives less heat. It does not heat the room more efficiently.

Differences between heater types are in how they deliver heat. Fan heaters warm the air quickly but cool down fast. Oil-filled radiators warm up slowly, then keep giving heat after the thermostat turns the element off. Infrared or radiant heaters warm people and objects directly, which can feel warmer if you sit close. If you only want to warm yourself at a desk, a small radiant heater aimed at your legs can feel warm while using only 500 or 750 watts.

Ways to cut a space heater bill

1. Heat the person, not the room. A small heater near your feet at a desk can do more than a large one heating the whole room.
2. Close the door and block drafts. Heat escapes through gaps under doors and around windows. Our guide to finding air leaks shows the cheap fixes that keep heat inside.
3. Use the thermostat and timer. Set the heater to 68 degrees or lower, and use a timer so it does not run while you are out or asleep.
4. Turn the main thermostat down, by several degrees, in the rooms you are not using. This is where the real savings come from. Without that, you pay for both the furnace and the heater.
5. Use a lower setting once the room is warm. Start on high to take off the chill, then switch to low.
6. Add warm layers, blankets and rugs. They cost nothing to run.
7. Put the heater on a hard, level surface and give it space. That is a safety matter, and it also lets the heater work properly.
8. Do not use extension cords with a space heater. See the safety section below.

How to measure your own heater's cost

The label is a useful guide but not the whole truth, because the thermostat makes the heater cycle on and off. For a real number:

1. Plug the heater directly into a plug-in power meter, if it is rated for the load. Check the meter's maximum watts first, because a 1,500-watt heater needs a meter rated for at least that.
2. Run the heater for a normal day, at your normal settings.
3. Read the kWh used, then multiply by your price per kWh.

The result tells you the daily cost, and you can multiply it for a week or a month. Many utilities also show hourly use in an app, so compare a day with the heater to a day without it.

Safety matters as much as cost

Space heaters are a common cause of home fires, and most of those fires are preventable. The Department of Energy and fire safety agencies give the same basic advice:

• Plug the heater straight into a wall outlet. Do not use an extension cord or a power strip, because the heater draws a lot of current and the cord can overheat.
• Keep it at least three feet (about one meter) from anything that can burn, including curtains, bedding, furniture and paper.
• Never leave it on while you are asleep or out of the house, unless it is designed for that. Choose a model with tip-over protection and overheat protection.
• Use it on a hard, flat surface, not on carpet, a bed or a sofa.
• Check the plug and cord. If the plug is hot or discolored, or the outlet feels warm, stop using it. If a circuit trips again and again, see what makes a circuit breaker trip rather than resetting it over and over.
• Keep children and pets away.

A heater that smells of burning plastic, sparks or makes a popping sound should be unplugged and replaced.

Space heater or a different heat source?

If you want to cut winter costs, heat-saving measures in the home often beat a space heater. Sealing leaks, adding a rug, closing curtains at night and lowering the thermostat a degree or two all reduce the need for extra heat. For a space that needs heat all winter, a heat pump or a mini-split system is usually far cheaper to run than electric resistance heaters, because it moves heat instead of making it. That is a larger purchase, but it can pay back over a few winters.

What we could not verify

Electricity rates change by state, utility and time of day, so the dollar figures here are examples rather than a guarantee. A heater's real running time depends on its thermostat, the size and insulation of the room and the outside temperature. A power meter or your utility's usage data gives your true number.

The short version

At 18 cents per kWh, a 1,500-watt space heater costs about 27 cents an hour at full power, around $65 for a month of 8-hour days. Multiply the label watts by hours, divide by 1,000, then multiply by your rate to get your own figure. A heater saves money only if you turn down the central heating and heat just the room you are using. Keep it plugged straight into the wall, away from anything that can burn, and never leave it running unattended.