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Natural Gas Versus Electric Garage Heater

by johnhaynesiv
posted 10-19-2011 02:19 PM

39 replies so far

#1 posted 10-19-2011 02:51 PM

I didn’t recognize the term ‘decatherm’ until I looked it up.
Approximately the equivalent of burning 1000 cubic feet of natural gas (a therm is approximately the equivalent of burning 100 cf of gas).
However the math turns out, it is good to realize the many electric power utilities burn gas to generate electricity, so in that case you would be paying the electric company to process the electricity into power that you would, in turn convert to heat. In many cases it would turn out to be inefficient.
My choice was a ceiling mounted gas furnace which draws outside air for combustion and has a power vented exhaust.
Still, I try not to run it except for important work. Social Security doesn’t provide that much for extras!

-- Will trade wife's yarn for tools.

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1854 posts in 2219 days

#2 posted 10-19-2011 03:02 PM

First off, you are not comparing apples to apples.

A 5000 watt electric heater will produce about 17,000 BTU. That might be enough to keep you warm, but would take a long time to heat the area from a cold start.

When I lived in Nebraska I had a similar sized garage workshop and I had a 12,000 BTU electric heater that would barely keep it comfortable on cold days. I used a 75,000 kerosene torpedo heater to bring it to temp, (it would only take about 5 or 10 minutes) then let the electric maintain the temp.

If it was really cold outside (5-10F) the electric couldn’t maintain the temp by itself.

So – I said that to say this. You need to have a qualified person calculate how many BTU’s you need on the coldest day you expect to use your shop.

-- Joe

View StumpyNubs's profile


6194 posts in 1458 days

#3 posted 10-19-2011 03:25 PM

I use a vent free wall mounted natural gas heater. It cost me a couple hundred bucks, I installed it myself and it keeps everything toasty warm even in the cold Michigan winters. I also have a 2 story house that I heat with a single vent free natural gas fireplace. I never use the furnace.

Why spend all that money? Go get the largest vent free wall unit you can get (It will cost less than $400). It will also cost a lot less to use because vent free is so much more efficient.

Don’t waste your money on one with a blower. It’s much better to just get a big exhaust fan and hang it from the ceiling near the heater angled toward the floor. That does a MUCH better job pulling the hot air down from the ceiling and circulating it throughout the shop. In fact, you can even build an overhead shop air filter that will double as an air circulator for heating. Just make it so it pulls air from the ceiling and exhausts it toward the floor.

It’s also well suited to your schedule. Set it on the lowest setting (buy one with a thermostat) and keep the air circulating when you’re not in the shop. It’ll keep things above freezing for next to nothing, and when you work in the shop it’ll take only a short time to warm up.

I’m telling you this from experience. You’ll be just as happy going this way and you can take all that cost savings and buy some nice tools!

-- It's the best woodworking show since the invention of wood... New episodes at:

View Pdub's profile


893 posts in 1838 days

#4 posted 10-19-2011 03:49 PM

I heat a 560 SF shop with a 5,000 watt electric heater. I live in North Dakota so it get pretty cold up here. I have 2×6 walls and blown insulation in the ceiling. My heater keeps it plenty warm in the shop, but I leave it on all of the time. I just turn it down if I won’t be working in there for awhile.

-- Paul, North Dakota, USAF Ret.

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Gene Howe

5663 posts in 2086 days

#5 posted 10-19-2011 04:13 PM

My shop is 36X28 with a 10’ ceiling. Like Sumpynubs, I use a ventless gas heater. Mine’s propane, and does have a blower, tho I’d agree, it’s not needed.
While it seldom get’s REEELY cold here, it has been -8 and the heater kept it toasty.
Our home’s well water pressure tank and pump is in the shop, so it MUST be above 30 at all times.
We are seriously considering installing one in the house, also.
Here is the one I use in the shop. ProComm

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

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Bill White

3457 posts in 2618 days

#6 posted 10-19-2011 05:22 PM

What do you do about the moisture created by the gas heaters? Don’t the unvented units generate a bunch?
I use an electric oil-filled radiator in my shop. 20’ X 20’ insulated well with dbl. paned windows. Seems to do a good job.
If it gets really cold plug up a second one.


#7 posted 10-19-2011 05:31 PM

I heat my whole 2 story house with unvented gas wall heaters. They do very well and are extremely effecicient. I have some concern for the use of them in my shop, however, because of the open flame.

In my experience with these heaters, I find that the blue flame type generates a lot of water, but the ones with the ceramic elements that generate infrared do not.


-- Will trade wife's yarn for tools.

View StumpyNubs's profile


6194 posts in 1458 days

#8 posted 10-19-2011 08:44 PM

The two issues raised about ventless heaters are, in my experience, non issues.

1. Open flame- I have a dust collection system. BUT- I don’t always use it. Sometimes there’s sawdust on the floor around machines and a thin layer of dust on everything, including the heater. The fact is, a piece of glass covers the flame. There is no way for it to jump out and set something on fire. I can leave a handful of sawdust on top of the heater (if I was so inclined) and it would never catch fire. I could even throw a handful of sawdust at the heater and most would never hit the flames. It doesn’t create sparks like a wood fireplace, so it is near to impossible for it to spread. I think it is as safe as any electrical element heater…

2. Moisture- I’ve read lots of stuff about them creating excessive moisture. But in reality I never notice a thing, not in the house or the shop. My wood doesn’t swell and my saws don’t rust. HOWEVER- as is the case with any heating system, letting it get down to below freezing and then warming it up every day will cause condensation and rust your machines. So keep it turned down but not off on those winter nights.

-- It's the best woodworking show since the invention of wood... New episodes at:

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103 posts in 1341 days

#9 posted 10-20-2011 12:44 AM

I have a vent-less 3 brick in my 2 car garage with a 18ft un-insulated garage door and it does fine at worst I have to leave one brick running.

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Fred Hargis

1794 posts in 1151 days

#10 posted 10-29-2011 03:08 PM

To me, the math of the choice is very simple…even with your low electric rate, nat gas is going to be cheaper fairly quickly. The price of your quote strikes me as being very high. I just installed a 45K modine style in my own shop last year (this one is a Sterling Garage Guy). Doing it myself, it cost about $800 for the furnace and venting. The wiring was already setup for the thermostat and power. I plumbed the gas (LP, in my case) myself. Even if your uncomfortabel doing such work, I would think you could buy the heater, hang it yourself and then have the connections done and still save money. BTW, 75K may be too much, I use the 45K to heat a 24×32x8 shop with R19 walls and R40 ceiling….and it’s way more than adequate. I realize my winters may not be as bad as yours (NW OHIO), but it’s still something to consider.

-- Our village hasn't lost it's idiot, we sent 'em to Washington.

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Fred Hargis

1794 posts in 1151 days

#11 posted 10-29-2011 05:03 PM

I should have mentioned in my previous post: the reason my heater was as high as it was ($800) is that I ordered with the direct vent kit (bring in outside air for combustion). That was almost $300 of the cost, and amounted to little more than about $75 worth of HVAC fitting and a custom box to hold it all together. The heater itself was about $400, and the rest was for things like a thermostat, fuel piping, etc. Would have just edited that post but ran out of time….

-- Our village hasn't lost it's idiot, we sent 'em to Washington.

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15698 posts in 2876 days

#12 posted 10-29-2011 05:33 PM

If you are paying eight dollars and seventy cents per kWh, as your post states, you should really go with gas. :-)

-- Charlie M. "Woodworking - patience = firewood"

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1578 posts in 1949 days

#13 posted 10-29-2011 05:45 PM

I just realized I have my electric bill right here at my desk, and Charlie’s reply prompted me to check for myself: I pay 9 cents per KwH for the first 450, then 12 per KwH in excess of that. This is in New Mexico. If you really are paying almost 100 TIMES that much, go gas.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

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9 posts in 1079 days

#14 posted 10-29-2011 05:52 PM

I’m off by a decimal point… The cost of electricity here in Utah is $0.87/KWh. it would still cost me $0.43 per hour to run an 5,000 watt electric unit.

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1578 posts in 1949 days

#15 posted 10-29-2011 08:07 PM

Still sounds like you should go gas. If what I pay is any comparison, your electric rate is still way out of proportion. You pay 46 cents per therm for gas; I pay 49 to 54 depending on the quantity, and you still pay 8 times what I pay for electricity.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

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Fred Hargis

1794 posts in 1151 days

#16 posted 10-29-2011 10:36 PM

I just assumed you were off by 2 decimal points….I pay about .0975¢ KWH.

-- Our village hasn't lost it's idiot, we sent 'em to Washington.

View TheBirdMan's profile


21 posts in 1062 days

#17 posted 10-30-2011 05:32 AM

John, I have the Hot Dawg HD30 in my 2 car garage and it is plenty enough. Depending on where one lives also makes a difference in sizing these units. Modine makes the HD/HDS 30, 45, 60, 75, 100, and 125. All the numbers refer to Btu/Hr Input, i.e. a HD 45 is 45,000 Btu/Hr. The HD is a power-exhausted, gas fired unit heater. The HDS is a separated-combustion, gas-fired unit heater (meaning it draws combustion air from outside the workspace).

If your garage is not insulated than most likely the HD/HDS 75 makes since, but generally speaking this unit is for a large garage (larger than a 3-1/2 car garage). If your garage is anything like mine that is partially insulated, attached to the house, below two bedrooms, with one wall of the shop being an underground foundation wall due to the house being a walk-out style ranch, than a smaller unit would work just fine.

These units can install 1” from the ceiling about 12” from the back to the wall, and about 6” on the other two sides. This gives you a lot of flexibility on where you put your heater.

As long as the unit is vented properly (which is very easy to do) you will NEVER have any kind of humidity problems with this unit especially since you live in UT where humidity is always low.

You will be very happy if you get any of the Hot Dawg’s, but if you are not comfortable installing one yourself than call another heating company for another quote. It does not have to be someone who sells a Hot Dawg because you first need to figure out what size unit you need. My guess is that you can get away with a smaller unit.

-- -- Pat, Colorado;

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Craftsman on the lake

2386 posts in 2095 days

#18 posted 10-30-2011 05:52 AM

I too have a ventless propane heater in Maine. Plenty cold but the heater brings it to shirtsleeve temperature in about 30 minutes at about 20 degrees outside. My shop is 25×25 with 7.5ft ceilings. All is well insulated though.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

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Fred Hargis

1794 posts in 1151 days

#19 posted 10-30-2011 03:00 PM

Quote from my earlier post: I just assumed you were off by 2 decimal points….I pay about .0975¢ KWH.

Obviously I was off by 2 decimals points as well…..should have used the dollar sign. It’s 9.75¢/KWH in my area. Sure wish we had a longer lived edit function here.

-- Our village hasn't lost it's idiot, we sent 'em to Washington.

View tenontim's profile


2131 posts in 2402 days

#20 posted 10-30-2011 11:23 PM

I had a HotDawg 45000 btu heater when I lived in Maine and it did a real good job of heating my 18×24 shop. I moved to Texas and installed a Modine garage heater. It’s a 35000 btu and it does a good job on my 24×24 shop. I think the price you’re being quoted is mostly labor to install. You might want to check around and find some friends that can help you install your heater and save some bucks. Check with the Greenhouse suppliers for your heater. I bought both of mine from I think they’re located in NJ.

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9 posts in 1079 days

#21 posted 11-02-2011 04:32 AM

I’m still capitulating here on which was to proceed… My neighbor has manage to sway me in the direction of an installed NG garage heater.

In my efforts to economize I’ve looked in the local adds and found this used Modine Garage Heater HD60. —->

The owner of this heater has indicated that he’s moving, had hardly used the machine, and it is 6-years old.

Am I nuts for considering this route?... or is it possible that I’m onto something good?

BTW: My garage is 35×22 x 10

#22 posted 11-02-2011 01:20 PM

It looks just like mine, but mine doesn’t have the Modine nameplate.
If its the same it will draw outside air for combustion and have a powered exhaust. That means it can be vented horizontally with no need for a vertical stack.


-- Will trade wife's yarn for tools.

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Fred Hargis

1794 posts in 1151 days

#23 posted 11-02-2011 01:23 PM

1;) you are not nuts 2:) it is possible that you are onto something good 3:) if you’re sure it works (shouldn’t be a problem) it would serve you well. 4;) I would bet that it’s still too large for our garage…my current shop (32×24x8) uses a 45K, and it’s more than plenty….I suspect a 30K unit would have been about right. Even so, I think you would be way ahead with that unit as opposed to anything electric.

-- Our village hasn't lost it's idiot, we sent 'em to Washington.

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2131 posts in 2402 days

#24 posted 11-02-2011 01:33 PM

It’s probably more heater than you need, but that’s ok, it’ll shut off sooner. I used a programmable thermostat on mine, and it kept everything from freezing at night and would turn up the heat before I went out to work each day. The price is definitely good on this. I think the 60K units run about $800-900. I think you would be way ahead of the game, even if you bought this and had it professionally installed.

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15814 posts in 1524 days

#25 posted 11-02-2011 01:45 PM

I have a 20×20 sq ft shop and since it’s small and a little crowded I like the idea of an electric heater rather than the open flame gas. I plan on installing an overhead electric in one corner of the ceiling when I can afford it. Right now I just have a small portable space heater.

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

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487 posts in 1797 days

#26 posted 11-02-2011 07:32 PM

1 Therm = 29.3072222 kWh
1 Decatherm = 293.072222 kWh

At 100% efficiency, you would pay $.087/kWh * 293 Decatherm/kWh = 29.3072222 = $25.491/Decatherm for electric heat.
So $4.6/Decatherm of gas heat seems like a better deal.

You will have to make some adjustments for efficiency to get the exact rate you are paying in either case, but unless one is 5 times more efficient I don’t think it will change which one is better.

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487 posts in 1797 days

#27 posted 11-02-2011 07:44 PM

One thing to be concerned about is whether you will be using flammable solvents or making clouds of sawdust around possible ignition sources. I primarily use water based finishes and empty the DC outside since I have a gas water heater in the garage.

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KMP Wood Designs

48 posts in 1306 days

#28 posted 11-08-2011 12:23 AM

I have a Detroit Radiant Re-Verber-Ray infrared tube heater – LD20-50N mounted from the ceiling in my garage. I chose this over forced air gas due to less risk of fire and not circulating any dust that might be suspended in the air.

We generally don’t have real cold weather for long periods of time here in Virginia so I keep my shop at 72 degrees. I prefer to work in shirt sleeves and don’t want to wait for the shop to heat up so it was an easy decision. I’ve had shops in the past where I used a portable space heater and felt I was wasting my time.

-- Jim, Virginia,

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5 posts in 1206 days

#29 posted 02-07-2012 05:20 PM

I think Payne Natural Gas Furnaces may be a good buy based on what I’ve read about them. They seem to have very efficient models that may be cheaper to run than electric garage heaters.

View jerkylips's profile


233 posts in 1228 days

#30 posted 02-07-2012 07:32 PM

couple thoughts.. Last winter our office building lost heat for a week, so we got these little portable electric heaters for our desks. (pictured below).

This one is 1500 watts.

I have a 2000 sq ft house & our furnace is 60,000 btu’s. It looks like you’re comparing the equivalent of 3 portable heaters to a furnace for a large house. It seems like there is an ENORMOUS difference in capacity between the two you’re comparing.

Also, someone had asked about whether your garage is insulated. If not, I would guess it would be most cost-effective to insulate, then be able to purchase a smaller heater – upfront costs and operating costs would be lower..

View BobM001's profile


388 posts in 988 days

#31 posted 02-07-2012 08:29 PM

For a shop in which you may want to apply finishes that may be flammable or just for the sake of not having dust in the burner section, I’d recommend gas fired separated combustion. These are sealed comustion,power vented with outside air intake for combustion air. Reznor UDBS series. The other thing is to do a “heat loss survey” for the space you plan to heat. If you are on a municipal power supplier, then by all means go electric. Figure 3414 BTU/KW and 1000 BTU/ CU FT Nat Gas. A “therm” being 10 MBH.

Now if you really want to go “delux” there are the 95% condensing furnaces that will be outside vent/intake. But you’ll have to have SERIOUS air filtration on one to keep the finned condensing section of the heat exchanger clean. An “Air Bear” 4” thick filter would do the job on that detail. But this type would require a duct system. Some manufacturers counter flow models can be converted to horizontal flow to hang like a unit heater. All it takes is $$$!

-- OK, who's the wise guy that shrunk the plywood?

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Mainiac Matt

4014 posts in 986 days

#32 posted 02-07-2012 09:49 PM

the Hot Dog mounts up high and out of the way….

75K BTU will heat up your shop in no time, so you won’t have to keep it very warm when you’re not using it

electric baseboards will use up precious wall space and it will take an hour to warm up the shop.


if you are spraying any flamable finishes, you should give very careful consideration to your ventilation, as the hot dog could be an ignition source.

-- Pine is fine, but Oak's no joke!

View dbhost's profile


5385 posts in 1890 days

#33 posted 02-07-2012 10:08 PM

Just for comparison sake, I wanted to mention…

I am coastal Texas, in a ~385 sq ft 2 car garage. My doors are R10 rigid foam / radiant barrier, ceiling R30 and radiant barrier insulated. The walls completely uninsulated, but sealed where I can to at least reduce drafts. This winter is admittedly quite odd. I have yet to even think I might consider turning heat on… I haven’t gone below 60 deg F overnight in there…

HOWEVER, this year like I said, has been odd…. Last year, we had plenty of hard freezes, 25 ish deg F nights etc, meaning the shop would, if I let it, get into the low 30s for 10+ hours. Considering I have exposed pipe within the uninsulated walls, as well as glues etc.. in there, not to mention I like to work out there, I keep a little 1500 watt oil filled radiator out there. I put it immediately next to my reverse osmosis tank to keep the pipes warm, set on low and it kept the entire shop in the mid 50s during hard freezes.

Not ideal temps, but not terrible either…

In all honesty, if I were able to relocate somewhere with cooler summers at the expense of having to deal with cold winters, I would make sure I had a separate building for a shop, with 2×6 walls, spray foam insulated and heated with gas. Electric is nice, but it is awfully expensive to run…

-- My workshop blog can be found at

View jerkylips's profile


233 posts in 1228 days

#34 posted 02-07-2012 10:55 PM

I was thinking about this post.. We had to replace the furnace in our old house. We knew we were going to be selling, so wanted to do it as cheaply as we could. My brother is an HVAC installer, so I actually ordered a furnace & AC unit online & had him install it for me. It was under $2000 total (I paid him $500 to do the install). We got a Goodman unit & it performed very well while we were there.

So I looked online – something comparable to what we got runs around $500 (45k btu unit). I would think something like this would work well in a garage & might even be cheaper than you’ve been looking at..

Goodman furnace

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Mainiac Matt

4014 posts in 986 days

#35 posted 02-09-2012 08:39 PM

mobile home furnaces are often available for short dollars and work fine for shops….. but nothing is going to take up less space than that Hot Dog….. except ceiling mounted radient maybe.

-- Pine is fine, but Oak's no joke!

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64 posts in 1002 days

#36 posted 02-20-2012 06:08 PM

With Gas you’ll be off cheaper over the years. I am wondering about the electricity price you posted. I can’t believe you pay 8.70$ for 1kwh. that would mean one lightbulb costs 8,70$ when beeing left on a day, the fridge ends up at 260$ a month… no way.

-- Whoever finds mistakes can keep them. English is a foreign language to me.

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487 posts in 1797 days

#37 posted 02-20-2012 06:35 PM

I think he meant 8.7 cents/kwh not 8.7 dollars/kwh.

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2529 posts in 1009 days

#38 posted 02-20-2012 06:41 PM

I installed one of these in my 2 car garage shop and it works great. Williams garage heater
At 30,000 BTU capacity it is plenty for a 2 car garage. It was easy to install. It draws combustion air from the oustside through the vent so no danger of shop explosion. You might need a bigger one for a 3 car garage.

Here is a link to Northern Tools guide to calculating the the BTU output you need. Here

-- Bondo Gaposis

View Sarit's profile


487 posts in 1797 days

#39 posted 02-20-2012 06:46 PM

75k btu does seem high. Are you sure you need that much? Most HVAC ppl recommend that you get one sized appropriate to the heat loss. Too much power and the system cycles too quickly causing premature wear on the furnace and lots of hot/cold spots because it doesn’t stay on long enough to completely circulate the air.

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