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Old 2012-02-11, 08:29 PM   #1
276YT
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Default o.p. savings with electric Geo vs. propane/ngas.

Any previous Poster and other residential Home-Owners would like to share their experience and operational (o.p.) savings with a GSHP system?
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Old 2012-02-22, 01:36 AM   #2
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Sorry for not posting sooner but today is the first time I have browsed this forum in a while. I have a ground source geothermal system that heats both my 800sqft home and my 748sqft garage. The problem I have in providing actual savings is; I started heating the garage when I commissioned this system where it was previously unheated.

Despite this, I am seeing utility bills no higher than I was before this system. I compared my bills with two other homes the same at mine in my area and I think I am actually paying less than both of them but I couldn't confirm if the 'utilities' were both Gas and Electric or just one or the other.

The kicker is; I am heating almost twice the square footage so it would seem I am saving 'half' on my bill. I am not, really, since I don't heat the garage to the same temp as the house. It's hydronic in-slab heat so I find I only need to have the floor temp at 70F to be comfortable to work out there. This gives me a 'room temp' of about 8C. Sorry for the mix of temps but the hydronic controls are in F and the remote 'room temp' indicator is in C.

This has been a great choice for me as the system doubles as whole home A/C in the summer and actually 'stores' heat to be used the following winter, in theory.

Overall, I am very happy with my decision and the installation and operating costs. Long term maintenance will be the only real 'unknown' but for now all that is required is an annual washing of the air filter for the forced air heat/cool in the house. I have a website with more info about it; mygshpproject.shawwebspace.ca and have also posted in a thread here about it too, which you may have already seen.
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Old 2012-02-22, 09:45 AM   #3
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Previous threads as an FYI:

http://www.digitalhome.ca/forum/showthread.php?t=58543 Heat Pumps

http://www.digitalhome.ca/forum/showthread.php?t=135384 Fuels
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Old 2013-02-18, 05:24 PM   #4
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I know this is an older thread but I thought I would chime in here.

I'm building a new house this summer and as an engineer I like to analyze things

I understand that geothermal you can realize COPs in the 4 range, and NG furnaces are about 96% efficient, which in effect means that the cost of the fuel (electricity) has to be (4/.96) or 4.17 times more expensive (or less) to be more economical to run.

I then normalized the cost per therm of electricity and natural gas, using my December gas and electricity bills, to see if electricity was 4.17 times more expensive(or less) which would justify the pursuit of a geothermal system.

For electricity, my December bill, including all BS charges (delivery, debt retirement charge, HST, etc) averaged 17.12 cents/kWh. With a conversion rate of 29.30 kWh/therm, electricity costs ~5.02 dollars/therm.

For natural gas, my December, including all BS charges averaged 21.26 cents/m^3. With the conversion rate of 2.83 m^3/therm for natural gas, the cost per therm (in dollars) is 0.602.

Therefore 5.02 dollars/therm(electricity) / 0.602 dollars/therm(natural gas) is 8.336, which means that for the rates I have documented above, electricity is 8.336 times more expensive/therm than natural gas. That means the COP of a geothermal system has to be 8.336 times higher than the natural gas fueled system for the cost of operation to be equivalent.

I have not seen a geothermal system with a COP higher than 6.

Therefore for the price of energy in my region, there is no business case for geothermal heating, as 8.336 > 4.16.

There is still some analysis that needs to be done to see if the cost of cooling with geothermal is significantly cheaper than a, say 15 SEER A/C unit to offset the increased cost of heating. Again, this cost would have to be offset from the increased initial cost of geothermal.

But if you're going from a strictly environmental stance, the geothermal system is more efficient in its use of energy, but its not cheaper.

BTW I'm in the Hamilton, ON area.
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Old 2013-02-18, 09:57 PM   #5
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Good analysis so far. Comments below:

I know this is an older thread but I thought I would chime in here.

I'm building a new house this summer and as an engineer I like to analyze things.

A load calculation to determine how much heat the house needs is a good starting point.

If you want to roughly determine the impact of different design options (heating, windows, insulation), try a energy modelling program. A good free one is Hot 2000 - produced by natural resources Canada.

The type of heating system has an impact not only of the capital cost of the equipment, but ductwork too...

Heatpumps need significantly more airflow to deliver the same amount of BTUs.

Geothermal needs around 400 CFM (that's cubic feet per minute) per ton or 12,000 BTUs/hr of heat. (the same goes for a/c units, geothermal or not)

Modern furnaces only need 222 CFM give or take per 12 000 BTU/hr of heat.

Heat gain is always much lower than heat loss in our climate, so generally a duct system designed for a furnace these days should be adequate for a/c but not necessarily a heatpump sized for heating.

For example a home with a design heat loss of 40 000 BTUs @ -20C could easily get by with a 2 ton (24000 btu/hr) a/c.

If you get a geothermal system, be sure it has a two stage compressor -> otherwise it will be oversized for cooling (to the point of not dehumidifying properly) or undersized for heating. (necessitating the use of expensive supplemental heat)


I understand that geothermal you can realize COPs in the 4 range, and NG furnaces are about 96% efficient, which in effect means that the cost of the fuel (electricity) has to be (4/.96) or 4.17 times more expensive (or less) to be more economical to run.

When it comes to environmental impact - along with cost, the efficiency of the power plant has to be taken into consideration.

A COP of 4 might sounds good, but goethermal may only offer a marginal improvement over a 95% efficient gas furnace, because the typical nuclear/coal/gas power plant is only 30-45% efficient. (note: some of the new gas plants are better -> in the 50-60% range)

No one knows what kind of power generation mix ontario will have over the life of the house, but the province has built a lot of gas fired plants. Coal appears to be going away and all of the nuclear plants will have to be refurbished or replaced in the next 20 years.


I then normalized the cost per therm of electricity and natural gas, using my December gas and electricity bills, to see if electricity was 4.17 times more expensive(or less) which would justify the pursuit of a geothermal system.

The price of nat gas is pretty much guaranteed to increase over the next 20 years, since - adjusted for inflation, it's pretty much as cheap as it ever has been over the last 30 years.

The cost of electricity will probably increase for at least the next 5 years since mcguinty has locked the province into a lot of renewable energy contacts. (many of which are for capacity which hasn't even come online yet) After that, who knows?


For electricity, my December bill, including all BS charges (delivery, debt retirement charge, HST, etc) averaged 17.12 cents/kWh. With a conversion rate of 29.30 kWh/therm, electricity costs ~5.02 dollars/therm.

17 cents /kwh seems a little high - did the subtract the fixed monthly charge and include the ceb. (a subsidy - 10% off all charges)

For natural gas, my December, including all BS charges averaged 21.26 cents/m^3. With the conversion rate of 2.83 m^3/therm for natural gas, the cost per therm (in dollars) is 0.602.

Therefore 5.02 dollars/therm(electricity) / 0.602 dollars/therm(natural gas) is 8.336, which means that for the rates I have documented above, electricity is 8.336 times more expensive/therm than natural gas. That means the COP of a geothermal system has to be 8.336 times higher than the natural gas fueled system for the cost of operation to be equivalent.

I have not seen a geothermal system with a COP higher than 6.

Therefore for the price of energy in my region, there is no business case for geothermal heating, as 8.336 > 4.16.

One thing to remember is that the COP only applies when the geothermal heatpump can heat the house by itself in extreme cold. Heatpumps (even geothermal) are often installed with supplemental heat strips, which only have a cop of 1.

There is still some analysis that needs to be done to see if the cost of cooling with geothermal is significantly cheaper than a, say 15 SEER A/C unit to offset the increased cost of heating. Again, this cost would have to be offset from the increased initial cost of geothermal.

Modern air to air a/c units have an effective cop of 3+.

15 BTUs/watt (that's what seer is) = a cop of 4.4.

However, SEER isn't very representative of performance in very hot weather. It's pretty much a seasonal rating which includes outdoor temps at which the average person wouldn't use cooling to begin with.

A/Cs carry an EER rating which is BTU/watt at 95F indoor/80F outdoor.

A 15 seer a/c has a EER rating of 12 give or take 0.5 -> COP of 3.5



But if you're going from a strictly environmental stance, the geothermal system is more efficient in its use of energy, but its not cheaper.



BTW I'm in the Hamilton, ON area.
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Old 2013-02-19, 07:35 PM   #6
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Then there's the unnaturally low price of natural gas. The winter before I installed my geothermal system, NG prices got up into the mid $14/GJ range and, since inflation typically only causes prices to rise, I figured I had a surefire way to beat high heating costs.

Ironically, it was those very same high prices that spawned all the exploration and ground-water-poluting production in the States that then drove the prices down to where they are now and have been from so much oversupply.

In hindsight, a condensing NG boiler would have been a far cheaper installation and way to heat my home but I would still have needed to buy an A/C system to get what I have now.

All I can do is keep hoping NG prices start to go up and then my investment might start generating some financial savings.
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