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How Much Energy do Space Heaters Use?

Tricia Christensen
Updated May 16, 2024
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Space heaters are typically not an efficient means of heating, especially compared to a central heat pump, geothermal heating, or solar energy. Small electric heaters can use about 3,000 watts (about 10,000 BTU/hr) and larger ones may use over 11,000 watts (about 40,000 BTU/hr). Fuel powered portable heaters are often less expensive to run, using about 2,300 watts (7,848 BTU/hr) to 4,100 watts (13,990 BTU/hr). Electricity is one of the most expensive energies to use to heat an area, costing about twice as much as natural gas to produce the same amount of heat.

Compared to Other Heat Sources and Appliances

Running an electric space heater that uses around 1,500 watts for 24 hours a day for a month would take about 1,070 kWh per month. In comparison, running a baseboard heater for the same amount of time would take between 100 and 500 kWh/month, while running a heat pump could use anywhere from 1,000 to 2,000 kWh/month. It's important to remember, however, that a space heater can only heat a small area, while a heat pump can do the same for an entire house.

In terms of comparisons to other household appliances, running a microwave takes about 25 watts (85 BTU/hr), while an oven uses about 5,000 watts (17,061 BTU/hr) and a refrigerator uses about 780 watts (2,672 BTU/hr). This means that a person could run a refrigerator for about four hours before using up the energy it would take to run a small space heater for one hour.

Electric vs. Combustion Heaters

Since fuels like natural gas are typically less expensive than electricity, combustion heaters are often less expensive to operate than electric models. Even so, they are not recommended for regular residential use since they require very good ventilation. Combustion heaters can produce poisonous fumes that build up and become a danger to people in the area if they aren't vented properly. They can run on natural gas, diesel, or kerosene, but never gasoline. Typically, these devices are only used in residential settings during an emergency power outage.

Using Space Heaters Cost-Efficiently

Even though space heaters do consume a great deal of energy, in some situations they are both practical and cost efficient. With a central heaters, every room is heated equally, even if some rooms do not require the same amount of heat. The advantage of portable heating is that warmth is easily directed towards a single area. If the central heater is set to low temperature, and a single room or portion of a room is warmed with a portable heater, it can be more energy efficient than using the central unit.

It is important to note that portable heaters are rated for specific room sizes. If a small heater is used in a large room, it will use a great deal of energy without providing enough heat. A large heater in a small space will use excessive energy and provide too much heat.

HomeQuestionsAnswered is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Tricia Christensen
By Tricia Christensen , Writer
With a Literature degree from Sonoma State University and years of experience as a HomeQuestionsAnswered contributor, Tricia Christensen is based in Northern California and brings a wealth of knowledge and passion to her writing. Her wide-ranging interests include reading, writing, medicine, art, film, history, politics, ethics, and religion, all of which she incorporates into her informative articles. Tricia is currently working on her first novel.

Discussion Comments

By anon353070 — On Oct 28, 2013

Ah, I long for the good old days when pot belly stoves were the norm. Those, and a good wool blanket kept everyone warm as toast. The bad part was going to the outhouse on a frigid night to take a poop! Still, it was better.

By anon311248 — On Dec 31, 2012

I have no clue why some seem to think that space heating is cheaper than home heating systems for heating a home. It is not just about efficiency. It is about the cost of the energy, and electric is more expensive than carbon fuels.

That is not to say that space heaters don't have their place. If you only need additional heat in small areas and individual rooms, there can be some savings. But for heating an entire house, they are an expensive option.

One last point: Heat lost from ducts to unheated areas can be an issue if they are in an attic or vented crawl space. But if it is lost in interior walls or floors, there is no real heat loss because it migrates into living areas, or prevents heat from living areas migrating into the walls/floors.

Basically, heat "leakage" within the building envelope stays in the building envelope. Duct leakage only becomes a major issue if it occurs in areas that you do not want to heat at all. But even in an unheated basement, some heat may very well be desirable.

By anon228534 — On Nov 09, 2011

This article is total crap. The typical space heater uses 600 watts (on low) to 1500 watts (on high). There is a huge difference between 600 and 3000 (five times for those that can't do the math).

Electric oil heaters are way more efficient than an old furnace, whether gas or electric, that's pumping heat through cold duct work and heating rooms that don't need to be heated.

By anon131232 — On Dec 01, 2010

Here is my take on this!

The one thing I have yet to see anyone remark on is the amount of efficiency loss of forced air furnaces. The feds report you only get 50 percent of of what you spend to make the heat -- heat loss through duct and up the flue depending on the type you have. Radiant heat of any type will be better.

Most of us can't rip our walls and floors open to improve the ducting and you will pull your hair out trying to find all the little nooks and crannies that allow cold air in from the outdoors especially when the furnace blower sucks it in from everywhere, like bathroom vents and those nooks and crannies.

Good radiant type heaters will work well to warm your living area. in my case one 1500w oil filled radiant is enough to passively heat the other rooms as well, not a lot but enough to not have the furnace come on. if you could convert your heater to radiant type of heat, that would be best but, too much expense for most of us in this economy. forced air stinks, in my opinion. the ductwork contains dust and loses too much heat. you should see how long it takes the furnace to heat up the ductwork alone!

In a perfect installation they would work well but, very few have that perfect installation. Portable radiant heaters allow you to choose which room will be warmer and the rest can stay cool. Just remember to set the thermostat so it is not on all the time and turn it way down or off when you leave. I use an air cleaner to move the air around a 1500w oil filled and the whole house stays warm enough for the electric furnace to stay off. my living area stays 67 and cozy, it is a pleasant type of warmth with no drafty feelings.

Again, forced air could be more efficient but the standard installation is equivalent to a 1968 VW beetle and it needs to be a 2011 Lincoln to be of any great value. This is not just my opinion. check out the studies for yourself! good luck (Think radiant).

By anon127349 — On Nov 16, 2010

A space heater cannot use 3000 watts. A typical breaker is 15 amps which equates to 1800 watts. A typical dryer or hot water heater consumes 5000 watts.

By aplenty — On Oct 16, 2010

Space heaters in general are a dangerous option for home heating. According to the U.S department of energy, portable, radiant, and kerosene space heaters start 25,000 house fires a year.

The best way to deal with winter heat and cold is to improve efficiency. Things like eliminating drafts, improving insulation, and other efficiency techniques can have a significant impact on indoor comfort levels. There are programs that help low-income people afford these improvements, and the government offers somewhere around a 15% tax credit for efficiency improvements. IT may cost a little more upfront to improve efficiency in your home, but you will save money in the long-term, receive a nice tax incentive, and reduce your family's exposure to risk.

By lokilove — On Dec 29, 2009

We use space heaters in the bedrooms only. They are cheaper (seems to me at least) than using the central to heat the whole house when we can just put on socks and a sweater.

I have stood staring at the electric meter with the space heater off, then when the space heater is turned on there is a VERY noticeable increase in the usage!

The combustion heaters just scream "accident waiting to happen" to me, even if they would be cheaper to run, I'm not risking it.

Tricia Christensen

Tricia Christensen


With a Literature degree from Sonoma State University and years of experience as a HomeQuestionsAnswered contributor,...
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