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Is an Electric Space Heater More Efficient Than Your Gas Furnace?

 

hvac electric space heater radiant heat

This time of year, I see a lot of ads for various types of electric space heaters. They all promise that you'll save money by using them rather than whatever other type of heat you have in your home. Some of them have famous—or formerly famous—people promoting them. Sometimes it's people who look like members of a small religious sect hawking these devices.

But are they correct when they say you'll save money by buying and using these small space heaters? The short answer is, probably not. All of these devices turn electricity into heat, which can be done at an efficiency of 100%. (This is true when we consider site energy only, not all the losses that occur between the power plant and your home. If we include those, the efficiency is closer to 30%.) If you have a natural gas furnace, its efficiency is probably in the 80% to 95% range.

But you can't compare just the efficiency of the energy used on site to make heat for your home. There are two factors you have to consider to determine if a small space heater will save you money:

  • The cost of electricity versus the cost of natural gas
  • The amount of space you're heating and how much heat you're adding to it

If you have a decent sized house and keep most of it fairly cool while moving a small space heater around to keep only yourself warm, then you might save money. The cost per Btu of heat for electric heat is generally more than double the cost per Btu for natural gas, especially with gas rates as low as they've been in recent years. It can be 3 to 5 times more than natural gas in some areas.

What that means is that you've got to use a lot less heat to save money with these electric space heaters. If you're into sacrificing comfort and convenience, this may work for you. The ads I see, however, all show happy homeowners being more comfortable than ever with these devices.

Using a small electric space heater is a strategy that can work, but be aware that the ads you see for EdenPURE, Living Pure, and Amish fireplaces don't tell you the whole story. They're really just expensive versions of the electric space heaters you can buy locally. See this review of the EdenPURE in the Mapawatt blog.

My advice is to check Consumer Reports if you're in the market for a space heater. And definitely don't go with an unvented gas space heater!

 

 

Photo by Paul.Carroll from flickr.com, used under a Creative Commons license.

Comments

I get this question all the time as an Architect from clients. Often an addition, an attic expansion, or a small out building may be difficult to reach or prohibitively expensive with a conventional system. I'd be interested to hear what you would recommend for these spaces? Electric floor mat? Hydronic electric baseboard? 
I have a small office studio outbuilding (120 s.f.)that I heat with an electric echonoheat radiant panel and it works great and is affordable to operate, of course the space is super insulated so it doesn't have to work too hard.
Posted @ Monday, January 09, 2012 6:41 AM by Stephen Reilly
Thanks for the plug Allison! I did a detailed analysis of electric space heaters vs. natural gas on our post here: 
http://mapawatt.com/2010/02/18/electric-space-heaters/ 
 
But many people who use electric space heaters don't have access to natural gas and have to use something more expensive like heating oil, so electric may make sense in that scenario.
Posted @ Monday, January 09, 2012 7:26 AM by Chris
We have permanently mounted electric heaters in our bathrooms as the only source of heat. They are on timers with a max setting of 30 minutes. Works great for showers, and there is no need to heat these rooms 24/7 when nobody is in there 90% of the time. Electricity is $.10 in our area, the heaters are 1500W. So we're talking $5/mo if the heaters are run 30 min each per day. In our area all KWH over 600 are 1/2 price, but we typically don't use 600KWH in the winter months. 
 
Other things to consider is that a gas furnace is attached to ductwork, which is the really efficiency downfall of central HVAC systems IMHO. The fan is space heaters does not reduce efficiency significantly seeing as most motors are low wattage shaded pole types that convert most of the energy to heat anyways. Maybe 5W of the fan power is used to drive the blade, the rest just heats up the motor. That heat will eventually find it's way into the room (where else can it go?). 
 
As far as using heaters for hours at a time like the commercials imply, I'll pass.
Posted @ Monday, January 09, 2012 10:10 AM by Bob
Even though an electric heater costs more per Btu, it can save energy if its use is limited and it allows the house thermostat to be set lower than otherwise. I use a small radiator type heater (the kind filled with oil) under the knee-space of my desk. 
 
In my projects, I often recommend inexpensive space heaters for problem areas like baths. I've also specified them for supplemental heat in super insulated homes that are centrally heated with a mini-split (note: mini-splits do not provide supplemental heat). 
 
Those heavily promoted heaters Allison refers to are way too expensive for their intended purpose. My DeLonghi only cost about $50. 
 
Although all electric heaters have the same effcieicny (100%, those that incorporate thermal mass will provide more even heat dissipation over time. Mass is less important in a bath where you only need heat for a few minutes. The best solution here is a baseboard or toe-kick heater, or one of those ceiling-mounted IR fixtures (250-watt). Use a 15-minute Intermatic wind-up wall timer for control.
Posted @ Monday, January 09, 2012 11:58 AM by David Butler
Just got an email add from Northern Tool that prices on space heaters have been cut from 259 to 179$. Do another blog next week and see if the price drops again.
Posted @ Monday, January 09, 2012 12:01 PM by George Reynolds
For a small very well insulated space, you also have to figure in the cost of the gas meter in the electric or natural gas equation. 
 
Here its $15/month even if you use zero gas.
Posted @ Monday, January 09, 2012 8:05 PM by Richard Patterman
Great point Richard. For example, if the DHW is the only gas appliance, an electric water heater often costs less to operate even though a gas heater would cost less per BTU delivered to the water. It's that darn meter fee! 
 
BTW, I advocate against forced air gas furnaces in super insulated homes. They can create comfort issues, and in most areas, a heat pump would be less expensive to operate. 
 
True story: a building science instructor in Ohio submitted a case study (his own home) to Home Energy. He described why he decided to heat his well insulated home with electric baseboard radiators. In the article, he complained that he was unable to get Energy Star certification even though his home was extremely efficient and economical to heat. The article was rejected by Home Energy's editorial board, ostensibly because it sent the 'wrong message'. Eventually the author persevered and the article was published in Jan 07. As it turned out, the article drew an unusual amount of positive feedback and the author, Allen Zimmerman, now serves on Home Energy's Editorial Advisory Board.
Posted @ Monday, January 09, 2012 8:51 PM by David Butler
+1 on the dang meter fee. The $15/mo meter fee for gas in addition to the 1/2 price electric in the winter for use over 600KWH has me seriously considering going all electric when my furnace finally fails. The issue is I'd have to change the water heater, dryer, gas grill, and no more gas for the fireplace starter.
Posted @ Tuesday, January 10, 2012 7:39 AM by Bob
The real stinker about the meter fees is that's where the utility companies are making their money. Rates in our area haven't gone up much, but the meter fees have doubled over the past decade (both gas and electric). So much for encouraging conservation. Why air seal and insulate when most of the energy price is built into the fixed monthly meter fee?
Posted @ Tuesday, January 10, 2012 7:46 AM by Bob
Allison -  
 
Regarding the units with fans - all of the energy input into the fans is converted into heat....so the cost per Btu of heat delivered isn't really higher than non-fan models....
Posted @ Tuesday, January 10, 2012 9:55 AM by John Semmelhack
Thanks for your article, and I agree with the most of it, however there are some scenarios when there is a huge difference in efficiency between the different space heaters (in detail: convection and radiant heaters). On my site I covered a similar topic with the article comparing gas heaters vs electric heaters where I compared the electric and gas portable heater solution from different angles, like safety, the type of heat they deliver and heating power. Hope it is helpful.
Posted @ Sunday, January 15, 2012 9:08 PM by Space Heater Reviews
Obviously trying to warm your whole house with electric heaters it will cost you more compared to natural gas. But if you use them cleverly the can help you reduce your heating bills. For example I use natural gas for heating the whole house and a portable electric heater supplementary in the living room for extra warmth. That way I don't need to heat the whole house at a high temperature but only the room where I spend most of my time.
Posted @ Friday, March 23, 2012 9:19 AM by Chris
Comments have been closed for this article.
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