Electric Heat vs. Gas Heat...?

[PatrickW]

With the prices of natural gas going up quite a bit over the last couple years, is an electric heater a viable option for somebody who lives in Minnesota?

For an average 3 car garage - doesn't need to be heated all the time - just when I'm working on cars & stuff in the evenings.

What say the Wisdom of the Forum on Electric vs Gas...?

Thanks,

- Patrick

 

[customperformance]

At my old house I had a 14'x24' single car garage and for space reasons I used 2 6' electric base board heaters to heat it. I heated it all winter long last year and it only made about a $30 a month difference on the house electric bill. I set the thermostat at around 40-50 when I wasnt working and when I worked in there I turned it up and in less than a half hour it was nice and toasty. Sometimes it would be so warm in there I would sweat when working and turn the heat down. If your garage is insulated and finished inside I would get a good electric heater and just use it when you work in it.

 

[alankulwicki7]

I live in Minnesota and I bought electric radiant heaters from these guys:

http://www.radiantsystemsinc.com/

I'm not exactly sure how much more gas would have been to run this winter but I kept my detached 24'x28' garage around 46 all of the time. When I was working in there, I would turn it up to 55 or so. I'm not an expert but I thought the heaters worked great. I installed them myself and they don't take up valuable floor space.

When I was doing my research last fall, electric radiant was a bit cheaper to run but it was also more comfortable. It heats up the objects and not the air so you also don't have to worry about changing filters, carbon monoxide, etc.

Let me know if you have any more questions. I'll see if I can answer them....

 

[Arizona Geezer]

Don't know about Minn.........but my wife had a heat pump put on my shop in AZ. I set the thermostat at 50 in the winter, and 80 in the summer, unless I'm out there. It hasn't raised our electric bill more than about 30 a month. I just adjust it when I'm out there, which is most evenings and weekends. As I approach retirement age, that may change when I have more timeon my hands.

 

[87SS]

keep in mind that most electric plants in the US are gas fired.

meaning that unless you are being served by a hydro or nuke electric plant your Electricity prices will be on the rise soon. And will be comparable to gas once again

 

[RWD]

I'm on the fence about this too. I only need heat when I'm in there, not 24-7. With electric heat you don't need to run a gas line or a flue. Power seems to be easier to run then gas pipe. Electric heaters have less maintenence (I think!) no burners to clean, and no open flame. Electric heaters seem to be cheaper too.

 

[PatrickW]

keep in mind that most electric plants in the US are gas fired.

meaning that unless you are being served by a hydro or nuke electric plant your Electricity prices will be on the rise soon. And will be comparable to gas once again

We do have a nuke plant a few miles away.

- Patrick

 

[Stuart in MN]

You may want to think about an electric unit heater or two. They're generally less expensive to buy and install than an equivalent gas heater, and will heat the space up quickly which is a good thing if you only turn them on when you're going to be out there working. Here in Minnesota I think the price of gas heat is still less expensive than electric heat, but for your purposes electric can probably work out well. Qmark, Berko and Dayton are decent brands; this page shows a selection of them: http://www.air-n-water.com/electric-utility-heater.htm

Edited to add: Good insulation is real important - otherwise, all that heat is just going right out through the walls and roof.

Edited again to add: You must live up by Monticello or down by Red Wing, if you're close to one of the nuclear power plants.

 

[59ctd]

I too am sitting on this fence wondering gas or electric. My 3rd stall garage/workshop is erected and covered. I'm working on interior stuff now - wiring and whatnot. I did install the in-floor hydronic PEX tubing before they did the slab. Now thinking if I need to run a major electrical feed out there or a gas line for the energy source. My intention is to keep it heated constant temp all winter.

Can a person calculate heat load and size a boiler themselves, or does that need to be done by a professional only? Any place someone recommends to go online to look for and purchase a boiler unit?

Thanks much guys (and gals).

-Deon

 

[HOTRODPRIMER]

I live in South Carolina and have electric heat/air in my shop,,,30'x40' very well insulated,,,,insulated rollup doors also,,,

My highest bill in the shop this past winter was right at 73 bucks,,,,,I was in it almost everyday and the heat is set on 60 degrees and using power tools,,,mig,grinders,etc.

I have a good friend that has gas in his shop,,,,not very well insulated,,,,,during the same period he said is power bill for the shop was close to 60 bucks but the gas bill was over $175 during that same month,,,now granted he makes a living in his shop so he can afford the added expense.

I'm not trying to say one is better than the other,,,,just sharing my story.HRP

 

[BowtieNut]

Well, this won't be alot of help because I'm not done yet, but take it for what it's worth. My neighbor put up a shop 2 years ago, and he used the in-floor hydronic heat, with an electric boiler. He keeps it heated all winter, and he said his electric bill was over $100 during the cold months (he has separate service & meter at his shop). He wanted to hook it up off-peak, but they wouldn't let him unless he has a backup heat source, even though it's not a living space (this is in Ramsey, Centerpoint Energy).
I got all the stuff for my system from the same place, but I will be going with a gas boiler. For me, running separate service to my shop was pretty expensive. I think it was over $2000 if I remember correctly (large lots, long ways to nearest transformer or whatever). Sorry, no comparison yet, but next winter I should be able to compare my cost to his.

One thing I may be able to help on, is where I got my stuff. Energy Products in Elk River. I got several quotes from HVAC places to install the hydronic heat system for me, and they were all over $4000. No way I could afford that, but then my neighbor told me about Energy Products. I just called and told them what I wanted to do, and they ran all the calcs and told me exactly what I would need, and sent me a quote with all the parts/boiler size/tubing requirements/prices. That was about $2000. They are VERY helpful! Their website is www.energyproducts.biz but it's a pretty crappy website. Like I said, I just called them, and they were very helpful, and faxed me a quote the same day. It seems like they tend to push the electric boilers, but they do have gas as well. Or for a garage, a friend of mine just used a water heater and that works too, just not as efficient.

Sorry this is so long, but hope it helps.

 

[Just A Beginner]

I have ONE QPH4A electric heater from Q-Mark.

It does a very good job in the 24x24 two car garage when the ambient is about 40 degrees out.
Takes about 2 hours to bring the thermal mass up in the garage (see another post on that deal).

A rarely see any difference in the electric bill as usually I am running my electric large air compressor at the same time to run the Glass beader. I use the heater sporatically.

Tom V.

 

[Jumpin Johnnie]

I too am sitting on this fence wondering gas or electric. My 3rd stall garage/workshop is erected and covered. I'm working on interior stuff now - wiring and whatnot. I did install the in-floor hydronic PEX tubing before they did the slab. Now thinking if I need to run a major electrical feed out there or a gas line for the energy source. My intention is to keep it heated constant temp all winter.

Can a person calculate heat load and size a boiler themselves, or does that need to be done by a professional only? Any place someone recommends to go online to look for and purchase a boiler unit?

Thanks much guys (and gals).

-Deon

DLausche,

On radiant floor applications you need to figure BTu's per Sq. Ft. To keep it at 50 to 60 degrees figure 15-20 BTu's per Sq Ft. 60 to 70 degrees figure 25-30.
If the tube spacing is 12" centers with 1/2" tubing the max Btu's will be around 25. Soooooo... total Sq. Ft X BTu reguired ='s size of unit. Don't over size the unit it doesn't to any good. Remember tubing size and spacing will determine the max output of the floor. An electric water heater may do the job just fine. A standard water with a 4500 watt element will produce 15,358.5 btu's. You can rewire the water heater so both elements come on and double the output. Don't forget you need an expansion tank, air seperator, air vent, fill valve, thermostat, and circulating pump.
E-mail with questions.
Jumpin.

 

[59ctd]

DLausche,

On radiant floor applications you need to figure BTu's per Sq. Ft. To keep it at 50 to 60 degrees figure 15-20 BTu's per Sq Ft. 60 to 70 degrees figure 25-30.
If the tube spacing is 12" centers with 1/2" tubing the max Btu's will be around 25. Soooooo... total Sq. Ft X BTu reguired ='s size of unit. Don't over size the unit it doesn't to any good. Remember tubing size and spacing will determine the max output of the floor. An electric water heater may do the job just fine. A standard water with a 4500 watt element will produce 15,358.5 btu's. You can rewire the water heater so both elements come on and double the output. Don't forget you need an expansion tank, air seperator, air vent, fill valve, thermostat, and circulating pump.
E-mail with questions.
Jumpin.

So am I understanding correctly that this helps me determine the output of the heat source (i.e. the slab)? I'll have to review my LoopCAD drawing at home tonight. I think I used a 9" or 10" spacing. I have about 450' (3 circuits) of 1/2" line in a floor that is about 380 sq. ft.

If I wanted to occasionally heat the adjacent double garage with a baseboard radiant heat off of this boiler would it make sense to go a bit oversize on the boiler or am I asking for trouble if I go oversize at all?

I am leaning towards a natural gas fired boiler at this time. There is just no way to get that much current load over to that side of the house unless I have them run a new main line outside from the transformer($$$$). Too bad I can't tap off of my neighbors power panel as it is only 20' away from where I need the juice to be.

Thanks for the info!
-Deon

 

[Jumpin Johnnie]

So am I understanding correctly that this helps me determine the output of the heat source (i.e. the slab)? I'll have to review my LoopCAD drawing at home tonight. I think I used a 9" or 10" spacing. I have about 450' (3 circuits) of 1/2" line in a floor that is about 380 sq. ft.

If I wanted to occasionally heat the adjacent double garage with a baseboard radiant heat off of this boiler would it make sense to go a bit oversize on the boiler or am I asking for trouble if I go oversize at all?

I am leaning towards a natural gas fired boiler at this time. There is just no way to get that much current load over to that side of the house unless I have them run a new main line outside from the transformer($$$$). Too bad I can't tap off of my neighbors power panel as it is only 20' away from where I need the juice to be.

Thanks for the info!
-Deon

Deon,

That's correct the amount of BTu's per sq. ft. will give you the size of the heating plant. Remember that's the amount of BTu's per hour needed to maintain the required temp. If I would have sized the tubing I would have firgured 9" spacing, to be on the safe side. The total sq. ft. of heated area times a factor of 1.3 would give you the total tubing reguired. Since your running 1/2" the max circuit length is 300ft. But, you must have equal circuit lengths so you have even water flow between circuits. Example: 380 sq. ft. X's 1.3 = 494 ft of 1/2" tubing. Divide the total tubing required by 300. This will give you the number of circuits required. 494/300=1.64 or 2 circuits @ 247 each. Another key to good proformance is not "over pumping" the system. The water needs to move slow enough to allow heat transfer to the slab floor. I know it sounds like a lot to remember but if you don't design it correctly you woun't be satisfied with the system.

Boiler vs electric water heater. Consider the boiler will only be 80-85% efficient. A water heater on the other hand is 95-98% efficient. Check this out at a Home Depot. Also consider your fuel cost. Natural gas around here is $1.35-$1.90 per therm and L.P. $165-$2.00 this past winter. Electricity is around 7 cents per KWh. Electric is the way to go here, So. IL.

380 sq. ft. X 25 BTu's/sq.ft.=9500. Remember the water heater will put out 15,358 BTu's. That's with one element (4500watt), requiring (1) 30Amp circuit. Depending on the distance a #10 wire will handle 30Amps.

If you want to use a hot water system for the other garage than you need to figure the heat loss of that garage and add that to the floor requirement.

I know this is a lot to digest but e-mail or PM and I can help.
Also check out the web site for In-Floor brand products for design help.

John

 

[chuckspeed]

I was thinking about this thread last nite when I couldn't sleep...

The answer has to do with heat value:

A kW of electricity has 3413 BTU of heat; a cubic foot of nat gas has 1000 BTU. That same kW costs (on the average) ten cents...The cu.ft. of gas costs about 1.2 cents these days (at least in my area). Solving for equivalent heat value (using electric as baseline) yields a 4 cent cost for gas against a ten cent cost for electric - a significant differential in overall heat value.

But wait - we're not done! The good news about electric is there is no loss of efficiency when converting to heat, where gas incurs some loss during conversion. Manufacturers 'rate' their equipment based on steady-state conversion efficiency at optimum conditions - reality can be quite different. The 'true' efficiency of an installed system is call the in-service efficiency. In the case of forced air, there is a period of time where the burner is firing and ALL the heat is going to heating the heat exchanger - or up the stack; NOTHING is going to heat the space. Depending on cycle time, this accounts for a 6% drop in in-service efficiency - on top of the 75-78% efficiency of an older 80% efficient gas unit. Efficiency drops a a result of corroded heat exchangers, dirty burner plates, etc. So...typical in-service efficiency #'s are more like 70% for a GFA (gas forced air) system.

Soo...We multiply the gas cost by 1.3 to account for conversion inefficiencies, and arrive at a heat value 'cost' of 5.3 cents per gas 3413 BTU against the 10 cents for same amount of electric heat. This difference is bound to get bettter - not worse - as the majority of electricity is produced from coal here in America, and we have substantial coal reserves. Nat Gas, on the other hand, is now an imported resource, meaning that we consume more than we are able to pull from our own ground. The disparity is still quite significant, so it will be a while B4 electrical resistance heat displaces nat gas as an economic heating solution.

Generally speaking, the only place electric heat works (from an economic basis) is in Quebec, where electric costs are around 2 cents per kW.

 

[PatrickW]

I was thinking about this thread last nite when I couldn't sleep...

Fascinating post, Chuckspeed.

My wife works with a Mechanical Engineer who specializes in exactly this sort of thing (HVAC), and he said that Electric is better in the area where we live (I would have thought that Natural Gas was better).

He took into account a pricing scheme from the local utility that deals with terms like "interuptible off-peak discount rate" and a rebate that they give if you purchase an electric heater.

IMHO, the price of Natural Gas is only going to go in one direction from now on: UP. (Electricity probably will too, though...)

- Patrick

 

[MN_Pete]

Let's take chuckspeed's post and do the same for propane vs. electricity.

Electricity has 3413 BTU per KWH. Use chuckspeed's figure of 10 cents/KWH
Propane has 91000 BTU per gallon. My supplier's current price is $1.55/gallon.

So with electricity, 3413 BTU costs 10 cents
With propane, 3413 BTU costs 5.8 cents
Applying chuckspeed's conversion inefficiencies factor of 1.3, 3413 BTU of propane costs 7.5 cents.
Closer, but electricity still costs more.

Now let's look at my situation as an example. I live in southern Minnesota.
I built a pole barn / shed and went through these calculations when I was trying to decide whether to heat it using electricity or propane. As said above, I can buy propane for $1.55/gallon (was higher this past winter).
My electric company's normal rates are 7.8 cents/KWH. But they also offer an "interruptable heating" option at a rate of 3.9 cents/KWH. The normal 7.8 cent rate is very close to the propane cost calculated above, but the interruptable heating rate is much less.

I was having electric service installed, so once I decided on electric heat I sized my electric service to handle the extra load. The electric heaters are installed such that they can be shut off by the electric company during periods of high demand (up to 4 hours at a time). The power used by the heaters is recorded on a separate meter installed next to the main service meter. So far (one winter) it has worked out nice, but I didn't use the heaters a lot because the building is still being insulated. By next winter the shed should be fully insulated and I'll be ready to use the heaters then.

Pete

 

[Jumpin Johnnie]

You guys are on the right track, but lets look at it this way. Let's say you needed 1,000,000 btus to heat your garage for the winter. If you get 91,000 btus from propane but it's only 70% efficient you need to multiply 91000X.70=63,700 btus. So, 1,000,000 / 63,700 = 15.7 gals of proane @ $1.60 = $25.12 to produce 1,000,000 btus with propane. Electricity gives you 3413 btus per KWh. 1,000,000 / 3413 = 293 KWh X .10 = $29.30 to produce 1,000,000 btus of heat with electricity. Not much difference in cost.
Jumpin

 

[Jumpin Johnnie]

One more thing, if you use an air-to-air heat pump you double the efficiency and cut the cost in half, $14.65. The other benefit...you added a/c to the mix because the heat pump both heats and cools.
Jumpin

 

[Jumpin Johnnie]

Using Pete's cost of electricity, it would only cost $11.43 to produce 1,000,000 btus of heat.
Jumpin

 

[W-Cummins]

One more thing, if you use an air-to-air heat pump you double the efficiency and cut the cost in half, $14.65. The other benefit...you added a/c to the mix because the heat pump both heats and cools.
Jumpin

Dam that's quite the trick, sounds like you could just hook up a lot of thouse and the power co would pay you to run them

 

[Kevin54]

Whether electricity or propane...if one is cheaper today, it will catch up with the other tomorrow. One utility company is not going to let another make more money than them. Something no one has replied about is wood for a backup heat source. Depending on what you are doing, a good airtight woodburner will heat up a garage relatively fast and maintain heat for quite awhile. If you are not painting or using a bunch of solvents, then a woodburner would reduce your utility bill significantly. I currently run propane but am looking into a woodburner for that reason. Propane in my garage runs me around $100 for a month and a half depending on the weather. I keep it around 45-50 in the winter when I am not in there just to keep things from freezing. A good used airtight woodburner can be bought for around $100-200, and depending on where you are at wood can be had for nothing to $100 a cord. So the wood backup along with electric or propane should make it thru the winter months with no huge impact on the wallet.

 

[Jumpin Johnnie]

Dam that's quite the trick, sounds like you could just hook up a lot of thouse and the power co would pay you to run them

No, you still pay the power co. Just a lot less.
Jumpin

 

[Jumpin Johnnie]

Whether electricity or propane...if one is cheaper today, it will catch up with the other tomorrow. One utility company is not going to let another make more money than them. Something no one has replied about is wood for a backup heat source. Depending on what you are doing, a good airtight woodburner will heat up a garage relatively fast and maintain heat for quite awhile. If you are not painting or using a bunch of solvents, then a woodburner would reduce your utility bill significantly. I currently run propane but am looking into a woodburner for that reason. Propane in my garage runs me around $100 for a month and a half depending on the weather. I keep it around 45-50 in the winter when I am not in there just to keep things from freezing. A good used airtight woodburner can be bought for around $100-200, and depending on where you are at wood can be had for nothing to $100 a cord. So the wood backup along with electric or propane should make it thru the winter months with no huge impact on the wallet.

Can't say your wrong about the cost of electricity going up in the future, but ask your self, when was the last time your power co. raised rates. Your gas co. raises the rates every winter when you need the energy. Most power companies have to apply for rate increases through some state commission. It usually take a long time to get a rate increase approved.
I have a geothermal heating/cooling system in my house and heat and cool for an average of $30 a month for 12 months. So for $360 per year I heat and cool my house. My electric rate is .07 and has been for as long as I can remember.
Jumpin

 

[Jumpin Johnnie]

Kevin54,

What about insurance for the garage with a wood burner?

Jumpin