Oil or electric boiler cheaper to operate?

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Old 12-18-08, 08:16 PM
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Oil or electric boiler cheaper to operate?

I have an old (1950's), but new oil fired boiler. I believe it is 125000btus. It is in my cabin so I keep the heat to about 50 degrees when not at the cabin and crank it to 68 when I am there. I have had the boiler running for about a month and have gone through close to 60 gallons of oil. An electric boiler that produces the equivalent of about 90000 btu would cost about as much as a complete fill of my oil tank (around $1200). My question is how cost efficient are electric boilers?
 
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Old 12-18-08, 09:16 PM
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Keep in mind one big snafu ... if you don't have adequate electrical service at the cabin, you won't be able to run it. How many amps is your service? If you have to upgrade it, well... that's probably a pretty major cost to justify.

The single biggest payback in energy savings is still, and probably always will be, improvements to the building envelope in terms of insulation and infiltration.
 
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Old 12-18-08, 10:25 PM
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Talking

It would depend on your electrical rates. Its pretty easy to determine boiler efficiency, and how many BTUs are contained in a gallon of #2 fuel oil or kero. Whichever you burn. If you have cheap hydroelectric, you might be make out okay.

Figure it this way. A kWh of electricity is equal to 3413 BTUs. A gallon of #2 fuel oil has about 139,000 BTUs. Figure how many BTUs you received from 60 gallons of oil (60x139,000) and divide that by 3413 to get the equivalent number of kWhours of electricity you'll need. At twenty cents per KiloWattHour I figure you're near 500 bucks of electric power to produce the same heat you received from 60 gallons of fuel oil. If your electrical rates are 6 cents per kWh it looks much better, obviously.

Pete
 

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Old 12-19-08, 12:13 AM
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An electric boiler, having no stack losses, is about 94 to 98 percent efficient, depending on how much insulation is in the jacket.

Radio is a bit low on the BTU content of number 2 fuel oil; it's closer to 142,000 per gallon BUT the losses on an oil fired boiler will quickly drop the overall efficiency to less than 70% for a boiler of your age. He is correct, however, that the total price of the electricity, including delivery charges and taxes, will have to be fairly low to beat out oil, especially with the lower oil prices we are seeing today. Even where I live with electricity going for just a shade over eight cents per kilowatt hour the oil would be a better value.
 
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Old 12-19-08, 07:30 AM
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Definitely more information was needed.

I do have a 200 amp service so I should be OK for electrical requirements. Electricity is 9 cents a kilowatt hour. Thanks for the figures. Now I have to get a calculator.

Mike
 
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Old 12-19-08, 08:33 AM
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No boiler guy...but I think something was missed.

Yama...you said "I have an old (1950's), but new oil fired boiler." Did you mean, old cabin but new boiler? New can be relative...lol

I know from reading on here, there can be huge differences between even a 10 y/o system and a 2 y/o system
 
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Old 12-19-08, 08:38 AM
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I would say that $0.09 per KWH would be about on par with oil at $2.87 per gallon.


A $/unit 0.09 - 2.87
B BTU/unit 3413 - 142000
C A/(B*1000) $/1000 BTUs gross 0.0264 - 0.0202
D Effective Efficiency 0.98 - 0.75
C/D $/1000 BTUs net 0.0269 -0.0269


The assumption there is 98% effective annual efficiency for electric and 75% for oil. Other opinions on these will vary but that's the general math.

With oil, I would think that the annual servicing would be more expensive (requires more cleaning and a combustion check, filter, nozzle) and you should also add in some amortization for the oil tank. Depending on where you live you may now only expect as few as 10 years if you have an insurance company like mine.

A 125,000 BTU electric boiler (35 KW) would take about 150 amps on its own, although if your oil boiler is 125,000 BTUs, an electric boiler of perhaps 90 MBH (27KW) might be better and the amperage requirement on that is 112.
 
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Old 12-19-08, 09:15 AM
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Two other things enter this equation.

First, a heat loss is needed for the cabin. That will give some idea on the BTUs that are actually required for his application.

Secondly, what about recovery time? Since the occupied space is dropped to 50 degrees, how long will it take to recover to 65 degrees when the cabin is occupied? That could be handled by a Cottage Sitter or similar device though.

Insulation improvements might also yield some big savings, but not enough information is given.

Pete
 
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Old 12-19-08, 09:17 AM
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Yama...you said "I have an old (1950's), but new oil fired boiler." Did you mean, old cabin but new boiler? New can be relative...lol
New cabin and new boiler. The boiler was made in the 50's. I had one plumber estimate that it's efficiency may only be 50.

Insurance people haven't asked about the age of the tank.
 
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Old 12-19-08, 09:22 AM
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Ahhh I see, the old "new to me" thing.

I guess if it was free or something...but man that boiler could be almost 60 yrs old.
 
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Old 12-19-08, 09:24 AM
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Pete said..Two other things enter this equation.

First, a heat loss is needed for the cabin. That will give some idea on the BTUs that are actually required for his application.

Secondly, what about recovery time? Since the occupied space is dropped to 50 degrees, how long will it take to recover to 65 degrees when the cabin is occupied? That could be handled by a Cottage Sitter or similar device though.

Insulation improvements might also yield some big savings, but not enough information is given.
I used the online Stantfin calculator to determine heat loss and came up with about 84000 btu. I am going to be adding an attached garage in the future with infloor heat. The cabin is very well insulated with R20 on most walls (R28 on two of the basement walls) and R40 in the ceiling.
 
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Old 12-19-08, 09:25 AM
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Doing an efficiency test would give some idea of how much you could save by installing a new oil system. That should done during the annual service. Right now oil consumption shows the amount of BTUs used for that period, but what if it could be reduced by 30 or 40%??
 
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Old 12-19-08, 12:41 PM
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I'm saying this totally in jest so please take no offense but if you have those R values in a cottage and have an 84 MBH heatloss then it either shouldn't be called just a cottage or you are in Siberia. My house isn't that well insulated and has a far far lower heatloss! LOL
 
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Old 12-19-08, 12:54 PM
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I see you are in Ontario. My cabin is in Saskatchewan. It has many very large windows and it is 1120 on each of two floors. Those are the numbers that I got using the Slantfin program.
 
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Old 12-19-08, 04:02 PM
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2200 sq ft ... 84MBH ...

That comes out to 38 BTU / Sq Ft ... that's awful high ... if your place is insulated as well as you say, I would expect something way less than 30 ... even low 20's ... but if there's TONS of glass... well...

Mike, if'n I wuz you, I'd recheck everything... wall factors, floor factors, design temps...

If your loss is largely from large windows, one thing that will surely help you is some cellular insulated window coverings ... let's say 50% of your heat loss is the windows... and you cut that by say a third ... that's a pretty big chunk of savings right there. Those cellular blinds would probably pay for themselves before you even gottem installed!

Even if those windows are modern triple glazed, you can easily double the R value ... even heavy insulated drapes ... puttem on a motorized rod with a solar sensor... open for sun, close when none... works even when yer not there...
 
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Old 12-19-08, 05:54 PM
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Thanks for all the input. I am going to redo my heat loss, but I thought I was pretty careful. I didn't mention that I also have a heated 3 foot crawlspace under the house. The windows still don't have any covering over them and they are only double pane.

Thanks again.
 
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