most efficient electric heaters

notsobright · December 2009

what type of personal heaters are the most energy efficient?

my guess is ceramic but I dont know for sure and I want to get something small in the 1000-1500w range for use in the campervan.

Ive propane and kerosene heaters allready so Im not intrested in those types of infos. just electric in this case.

most everything AC powered is 1500w and my inverter is 1500w, I guess that it will run a 1500w space heater, I'd like to find a 1000w one but so far everything Ive seen is 1500w.

I think a direct DC powered electric heater might be better, I still need to look into those too.

thanks

Cariboocoot · December 2009

Re: most efficient electric heaters

Electric heaters aren't very efficient.

Of all the types I've had over the years I like the oil-filled radiators best. You get a choice of heat ranges (usually 600-900-1500 Watts) and their on/off cycle is more even than other types due to the retention of heat by the mass of the radiator. They are also safe to touch when on (not burning hot).

Direct DC heater is bound to be expensive due to the need for a thermostatic switch capable of surviving high-Voltage DC. Low Voltage DC draws large Amperage, which has similar control problems.

Running either off batteries and/or inverter is tough; heaters use and waste a lot of power.

What's wrong with propane?

notsobright · December 2009

Re: most efficient electric heaters

hey 'Coot!

I like my oil filled one the best too in the house but I havnt found a small one yet.

I hadnt thought about the DC switching. good point, thanks

propanes great when its available.

icarus · December 2009

Re: most efficient electric heaters

There is no such thing as a more efficient electric heater. All resistance electric heater put out the same number of BTUs per KWH. The only difference is how the heat is dispersed. An oil filled heater will heat up slower but hold it's heat in the thermal mass and release it slowly. A simple heater (like a toaster) will just get hot while it's on, and then cool rapidly when it's turned off.

Just as an fyi, running electric heat off of any PV solar system is almost impossible. Even the draw of a toaster for a few minutes a day is too much for most small systems. It is much more efficient to turn sun into heat directly rather than turn it into electricity then back into heat.

A 1500 watt heater will use 1.5 kwh/per hour. My TOTAL usage for a day, from my 300 watt system is ~.5 kwh. That's 500 watt hours for the whole day. If you are considering using electric heat on the small system you are talking about on other threads you are going to run into trouble.

Even though you aren't interested in other options, gas/propane/fuel oil/ kerosene etc are way better alternative.

Tony

Cariboocoot · December 2009

Re: most efficient electric heaters

Tony's right, of course. But if you must have electric heat ...

I use one of these to keep the well shed from freezing when it gets really cold in the Fraser Valley (what we call "Summer" in the Cariboo!

):

http://www.canadiantire.ca/AST/browse/3/HouseHome/1/HeatingAirConditioning/PortableBaseboardHeaters/PRDOVR~0435837P/Lancaster%2BMini%2BOil%2BFilled%2BHeater.jsp

Don't know if it's available in the US.

Sometimes Canadian Tire is a good place to buy things!

notsobright · December 2009

Re: most efficient electric heaters

icarus wrote: »

The only difference is how the heat is dispersed.

Tony

so which types disperse most efficiently?

BTW there could be a time when heat just might be the most important and only load on my system.

'Coot, that is a really neat little unit there!

thanks

icarus · December 2009

Re: most efficient electric heaters

Marc,

Are you enjoying the current Frasier outflow Northeaster? Gonna be -8 by later in the week!

Tony

PS Where is your new house?

icarus · December 2009

Re: most efficient electric heaters

notsobright wrote: »

so which types disperse most efficiently?

BTW there could be a time when heat just might be the most important and only load on my system.

'Coot, that is a really neat little unit there!

thanks

Perhaps I wasn't clear. There really is no such thing. Plug in 1000 watts of resistance electric heating element be it toaster/hair dryer/oil filled heater/ceramic and you will get ~3340 BTUs into the room every hour. It isn't like a gas burner which different designs get more (or less) BTUs into the room than some other design.

So to repeat, there is not such thing as a "more (or less) efficient" electric heater, despite what snake oil sales pitches say to the contrary. See the "Amish Hearth" BS.

As for your note about the heat being the only load. If memory serves you were looking at ~300 watts of PV and 200 ah of battery. The 200 ah of battery drawn down to 50% would yield ~2.8 kwh of power, enough to run your 1500 watt heater for just under 2 hours.

The same 2.8 kwh of power will probably take ~19 hours of full sun to recharge. Remember, under ideal solar installation, most people are lucky to get 4 hours of good sun per day, so running your heater will cost you ~ 5 days of charging.

Icarus

Cariboocoot · December 2009

Re: most efficient electric heaters

icarus wrote: »

Marc,

Are you enjoying the current Frasier outflow Northeaster? Gonna be -8 by later in the week!

Tony

PS Where is your new house?

Tony, it's -6 right now and the night is young. There's a good windchill too. Supposed to get even colder by Tuesday. That's why the little heater is on.:D

Moving up to 100 Mile House (a town name unique in the world, I bet

) where -8 is considered 'balmy'.
For those who don't know, Cariboo Winters are known to hit -40 - which is the same on either scale.

Marc

icarus · December 2009

Re: most efficient electric heaters

Well, you could be in 70 Mile House, or 150 Mile House! I always liked cold better than hot. In the Cariboo you get both!

Good luck,

T

notsobright · December 2009

Re: most efficient electric heaters

Ive read that elsewhere too but I just find it hard to belive/understand that all electric heaters are created equal.

the different designs and materials in various units doesnt change the over-all efficiency of them?

youve taken electrodynamics into consideration but mabey not thermodynamics.

mabey it doesnt matter but it seems it would. I dont know.

right now Im @346wats PV and 400ah available onboard with three seperate batteries. considering a 500w heater should change things. now if you wish go figure..

Im also in the SE USA and rarely see sub freezing temps so I think I can manage to come up with a reasonably decent back-up electric heating alternative that will work better than nothing.

I enjoy defying convention Icarus, havnt you noticed that yet LOL

mike95490 · December 2009

Re: most efficient electric heaters

notsobright wrote: »

what type of personal heaters are the most energy efficient?

They all have the same 100% conversion of electricity to heat.

IR (red glow coils) heat objects, not air. Ceramic grid (with fan) heat air.

A heating pad, heats whatever you set /wrap on it. Electric blanket.....

You need to define WHAT you want to heat, then use the right heater for it.

Cariboocoot · December 2009

Re: most efficient electric heaters

Electric heaters don't draw their rating all the time their on, of course. Predicting how much they will use in advance is impossible, as it depends on how often they have to cycle. The colder it gets, the more they use.

But even 500 Watts is hefty to an off-grid system. And you have both the draw-when-on consideration (ramps up the DC current something wicked) and the cumulative use eating into the battery capacity. Even at 50% cycling, that's 6 kilowatts per day. More than double what I use in running everything on the system.

What's worse, in no electric heater does the Wattage rating translate directly into btu's of heat; their efficiency losses are considerable, and you probably won't find figures anywhere on just how bad any given unit performs. Certainly the manufacturer isn't going to tell you.

You'll probably need super insulation and a lot more PV/battery for any such set-up to work well.

I know; I've thought about such a scheme as a safe way to heat a workshop at the cabin. One ting wrong with open flame heaters; risk of combustion no matter how well installed. I finally settled on the idea of solar thermal for heat. Maybe you should explore that avenue for your application.

BB. · December 2009

Re: most efficient electric heaters

Where/how you apply the heat can differentiate electric heaters... For example, if you want to prevent you pipes from freezing in the house--you can heat the entire home, or you can run "heat tape" (resistance heater tape) along your pipes and wrap them very well in insulation...

Big different in energy usage for that application. Of course, that is not going to keep your person any warmer. Whereas using propane heat to keep you warm will keep the pipes warm "for free".

There are alternatives to pure electric heat... The most common (and probably most practical) is the "heat pump". Think of a window air conditioner unit. Normally, blows cold air in the home and hot air outside the home. But, flip it in the window during cold weather, the hot air is blown in the home and cold air blown outside.

A heat pump does not "make heat" from the electricity... It actually moves heat from one place to another. And, for above freezing conditions, it can do heat a room (very roughly) 3x more efficiently than just a plain electric resistance heater can.

However, because it is taking heat from outside and bringing it inside using a refrigeration pump--the heat pump gets less efficient as the outside temperature falls.

A way around the falling outside temperature is to use an alternate source of heat--such as a water well, lake, or buried heat exchanger in the ground (trenches or wells).

Anyway--for an off-grid solar system, the Sanyo Mini Split discussed here earlier has a heat pump option (as I recall). I am sure others do too.

Sanyo mini split AC (inverter/variable speed)
smallest, most efficient A/C ?
SANYO 190'S WHATIS THE TRUTH

Note, even though this is a small and efficient system that seems to play well with off-grid systems, it still needs a minimum of 300 watts or so to operate. So, you need a good sized off grid system to use it.

And for warm climates, there are heat pump based Hot Water Heaters that can work pretty nicely if natural gas is not available--and if you use A/C a lot for your home, you can get hot water for free (desuperheater attached to home A/C system).

And, there are alternatives for heat too... A water cold genset makes power to recharge your batteries and the waste heat can be plumbed into your home (fancy term is co-generation).

Lots of alternatives out there--Best is to define your needs, then look at what may meet them based on your locally available energy sources (sun, wind, water, wood, etc.).

-Bill

icarus · December 2009

Re: most efficient electric heaters

Notso,

You may enjoy thumbing your nose at convention, but you can't thumb your nose very long at physics. 1 kwh is going to produce ~3400 BTUs no matter how you cut it. (Not counting any additional energy required for fans/controls etc).

As I stated in post #2, the equation is all the same with RESISTANT electric heat. As Bill suggests, heat pumps are a different equation, but the reality is you are NEVER going to power a heat pump with a system of the size you are building.

300 watts of PV would on an ideal day produce ~600 watthours of electricity out of the inverter on an average day. As I have also suggested, your 400 ah battery, drawn to 50% might put out ~ 2.4 kwh, but remember inverter efficiency might reduce that to ~1.9 kwh, enough to run you heater for under four hours. Once again, it would take ~ 3 days to get that charge back.

I second my suggestion that you would be further ahead with less cost, to use the sun for direct solar heat. Pv is lucky to get ~15% efficient. Solar heat is typically better than ~30%.

Tony

Cariboocoot · December 2009

Re: most efficient electric heaters

I see I've done my usual poor job of explaining myself. The use of "efficiency" and "btus" in my last post is highly inaccurate. People around here know I'm the first one to start spouting that all energy eventually comes down to heat. So I'm trying to explain the difference in, I guess you'd say "quality" of heating between types? No, that's not right either. So let's go to the life-time experiences box and pull out an example.

In my opinion, you want the room "comfortable". This is vague criteria, but it generally means warm air to move through so the people don't feel cold.

I used to live in a house with a poor central heating system that never kept the bathroom warm. To compensate, I tried three different types of heaters over the years. Each one was rated at 1500 Watts.

The first was a quartz tube infrared. It was terrible. You could feel the heat if you stood in front of it, but its action on the air was little and it relied on heating the mass in the room which then radiated back to the air. Very inefficient conversion of power used to warmth felt.

The second was a conventional fan-forced exposed element type. This was best for heating up from cold, because the fan would move air across a very high-temperature resistance heating element. Not so good for maintaining temp for the same reason; fairly noticeable fluctuations.

The third was the oil-filled radiator. Not good at heating from cold, as there's no fan and the surface temperature is quite low compared to the previous example. But excellent at maintaining room temperature as convection currents circulate air slowly and keep a fairly consistent over-all air temp throughout the room.

Notice how heaters say they're good for 'so many' square feet? First problem: rooms are three dimensional. Second, how warm do you want it? This is the data they don't give, whereas a conventional btu rating can be used to calculate how much volume you can heat how warm.

And remember: a block heater for an engine is also 1500 Watts, but you couldn't heat a room with it. well, I suppose you could but ...

(Similarities between this discussion and the tankless/tank water heaters discussion.)

icarus · December 2009

Re: most efficient electric heaters

Marc, I think your description of various heater types is pretty good. Quick heat (into me!) usually means drafts, and wild swings. Slow heat (oil filled) mean more even heat, but much slower getting into me! Low velocity fan forced over mass heaters, like the oil filled are a pretty good compromise.

So if the OP had asked "which electric heater was BETTER" for such and such a use", then a subjective answer might be made. But there is no answer for which is most efficient.

Not being facetious, but perhaps the "best heater" for the OP, to run on his PV system would be an electric blanket, preferably a DC version. Small enough draw that you could run it for a while. You would be heating just what you want heated, you! Wrap antoerh blanket over you and the run time would be pretty small.

Also, electric socks, boot heaters, gloves etc. If the goal is to keep warm, certainly something to consider.

Tony

notsobright · December 2009

Re: most efficient electric heaters

everybodys insisting on other ways and I understand that and why but thats not the topic.

if I had the resources I would conduct my own experiments in a controlled environment. like having a very large styrofoam cooler inside a well regulated room and setting many different types of electric heaters inside and measuring everything over time.

there has to be a certain design that is the most efficient for warming and maintaining a certain air temp.

so is it basically all of you are sure that any difference is insignificant enough that it wouldnt really amount to enough to consider.. is that it?

and why are the 500w electric heaters only available outside the USA? in Canada and UK mainly. seems everything available in the USA starts at 1500w. thats unusual, I wonder why that is? because its the land of the mighty V8s?

its hard to get anything small here! freezer, air conditioner. Im just way to conservative for the average american. I want a 2500btu a/c and a tiny freezer too

BTW I have 12vdc electric blanket and heated insoles and such (grips on my bike) but thanks anyway.

BB. · December 2009

Re: most efficient electric heaters

We have had many conversations about the Sanyo Mini-Split that goes down to 300 watts for a 3,000 BTU A/C... Works very nicely with off-grid systems (does not require 3,000 watts surge to start for example). And they have heat pump versions that are more efficient than resistance type electric heaters too (again, down to 3,000 BTU / 2.6 amps at 115 VAC).

In the end, a resistance heater outputs Watts=Volts*Amps ... There is no correction factor for ceramic, IR, oil filled, etc. Most people probably get high wattage heaters so they can heat the room quickly and then turn down/use thermostat to regulate the heat.

However, if you want something more efficient than a simple resistance heater, then you would have to pay more for the more complex Heat Pump type unit.

I find our 32" LCD TV, in our now well insulated home, does a fair job of keeping the room warm during cool evenings. Our own "150 watt" low power heater.

-Bill

niel · December 2009

Re: most efficient electric heaters

if you like something along the lines of radiant heat you might want to consider an infra red heater (quartz) as you will feel it quicker than the oil filled type. ceramics feel good too, but the majority of the heat is going straight to the ceiling with those types. infra red still are usually 1500w, but some are able to run at half of that as each tube is usually about 700-750w. as far as efficiency goes, no matter what you use the best you can hope for is about 3.4 btus per watt with a heat pump as the better exception to that, but as far as getting those btus to you i'd say infra red for a room if you can't wear something like an electric blanket as that puts the few btus it makes right there for you so fewer btus are needed and thus less power generally required.
does this help?

Windsun · December 2009

Re: most efficient electric heaters

notsobright wrote: »

if I had the resources I would conduct my own experiments in a controlled environment. like having a very large styrofoam cooler inside a well regulated room and setting many different types of electric heaters inside and measuring everything over time.

And if all the heaters were the same wattage, you would end up with the same results. You can believe any marketing or advertising that you want, but you cannot get around the laws of physics - 1000 watts converted to heat is a 1000 watts, no matter how you do it.

there has to be a certain design that is the most efficient for warming and maintaining a certain air temp.

Adding a fan will circulate the air better, keeping it at a more even temperature, but the average temperature and heat produced will not change.

and why are the 500w electric heaters only available outside the USA? in Canada and UK mainly. seems everything available in the USA starts at 1500w. thats unusual, I wonder why that is? because its the land of the mighty V8s?

Despite your remark for V8's, it has nothing to do with that. It has a lot to do with the fact that many other countries - and I have lived in several of them - do not have the house wiring or outlets good or heavy enough to support more amps.

its hard to get anything small here! freezer, air conditioner. Im just way to conservative for the average american. I want a 2500btu a/c and a tiny freezer too

Not that hard, just not common. And one of the reasons is that if you look at the specs for many of those small appliances, they are less efficient, not more. A large freezer is more efficient than a small one due - once again - to physics. The ratio of outside surface to inside volume is better in larger ones.

Cariboocoot · December 2009

Re: most efficient electric heaters

Well America has been brought up on a diet of large everything but ... It's more true that most other countries, like Windsun says, have the opposite problem; not good enough power source/distribution for higher-powered equipment (which is usually more efficient).

As for actual efficiency differences in heaters ... You might find that some lose more of their power consumption to low-level heat production (loss) in wiring than others. But otherwise it's more a matter of the subjective "comfort conversion" as I mentioned before.

If we sometimes seem overly negative here, don't blame us! It's that nasty man Sir Isaac Newton!

icarus · December 2009

Re: most efficient electric heaters

I'll repeat it once more!

"Perhaps I wasn't clear. There really is no such thing. Plug in 1000 watts of resistance electric heating element be it toaster/hair dryer/oil filled heater/ceramic and you will get ~3340 BTUs into the room every hour. It isn't like a gas burner which different designs get more (or less) BTUs into the room than some other design."

Windsun note: In fact you could use 1000 watts of light bulbs and get the same BTU.

You can go out and buy one of EVERY model of RESISTANCE heaters made, from 500 watt models to 10kw industrial heaters, and the result will be exactly the same,,,, ~3340 btu's per KWH! (less tiny little system differences for control boards etc).

The ONLY real difference will be how you feel that heat! Once more, if you wish to explore heat pump options, that is a different conversation.

Tony

notsobright · December 2009

Re: most efficient electric heaters

notsobright wrote: »

so is it basically all of you are sure that any difference is insignificant enough that it wouldnt really amount to enough to consider.. is that it?

a simple yes/no must be too umm.. too simple LOL

I think some people make it hard on themselves just by trying to make it hard on some one else.

the sanyo split is very apealing. (thinking to myself) how hard would it be to make it portable? ;-)

anyway, thanks for the input.

niel · December 2009

Re: most efficient electric heaters

if you want a yes/no answer then, yes, it is too insignificant on differences. what we tried to elaborate on is that it depends on your application and your preferences as to which method or wattage (depends on availability of product specs too) to employ.

icarus · December 2009

Re: most efficient electric heaters

Sanyo mini split is quite expensive (multiple thousands) and is not portable!

Tony

LucMan · December 2009

Re: most efficient electric heaters

Most comfortable electric heat is infloor radiant.
Not portable. Unless you could find it in rubber mat form.

http://www.nuheat.com/sustainability/nuheat-as-a-heat-source.html

TnAndy · December 2009

Re: most efficient electric heaters

icarus wrote: »

So to repeat, there is not such thing as a "more (or less) efficient" electric heater, despite what snake oil sales pitches say to the contrary. See the "Amish Hearth" BS.

Icarus

I'm glad you brought up that fool "Amish" heater......I nearly roll in the floor when I see full page ads in the Sunday paper touting them.......ahahahaaaaaaaaaa.....

niel · December 2009

Re: most efficient electric heaters

is that the same one that bob villa was pushing by saying it saves you money or am i thinking of another?

notsobright · December 2009

Re: most efficient electric heaters

just bought a sunbeam 1000w manual electric heater for $10 at Walmart

it was $10 what the heck! one year warranty on it.

on the box it says "save upto $106 this winter" "see details on back"

on back:

Based on the average of houshold heating systems being cycled off for a total of ten hours a day and using this heater for a total of ten hours a day for suplimental heat for the 25 weeks of winter. savings may vary.

yeah right.. it does heat very nicely actually seems better than both my similar 1500w units I havnt checked yet.

I also pulled out an old 1500w ceramic heater I had that doesnt work very well and checked it with the killawatt meter. its using 300watts on high! the heat is hardly noticable.

I pulled it apart and checked the wirring and its getting full voltage to all the right places. just doesnt get hot like it used to.

I have another ceramic that did this too except it quit heating all together.

I think I will avoid the ceramic types from now on.

GreenPowerManiac · December 2009

Re: most efficient electric heaters

It's funny you guys say electric heaters. I have modified 7 electric oil/radiator type heaters to the "Amish Hearth" type about 5 years ago when electricity pricing was regulated around here. My style is a bit different, however, I'll show a picture of one later on.

This is a multi-speed cpu fan with D/C voltage controls & A/C electric heater. And I could use the 600,900, or 1500 watt option.

The setup kept the heat from going up up and away. Low volume horizontal air flow and multi-directional if needed. Cost about 15 bucks to modify this way. "High efficiency" ? is a different question.......

most efficient electric heaters

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