# Geothermal vs Wood Boiler



## PlayWithFire (Jan 23, 2014)

At $160/cord (my current price) and $0.14/KWH (generation+transmission).  The estimated cost of running a geothermal system is nearly identical to a wood boiler, maybe even less.
http://www.vermontgeo.com/geothermal_operating_costs.html

The install cost of geothermal with ducked work might be around $25k after 30% Gov rebates. The cost of wood boiler is probably about $15k.  Geothermal adds about $14k to the resale of a home.  Wood Boiler doesn't add anything to the resale of a home and may be seen as a negative (source: my real estate agent).

I currently get about 90% of my heat from a wood insert, but the time has come for an upgrade.  I was thinking wood boiler, but my wife suggested geothermal.  After looking at the numbers, I must admit it would be nice not to spend hundreds of hours a year stacking wood.

Thoughts?


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## leon (Jan 24, 2014)

Speaking as a certified water well driller and pump installer;

If you have a large property you can bury the piping over long distances
at a five foot depth for a ground source heat pump.

Drilling a well depends on the water table depth and whether you have enough
water to drill two wells at different depths using one for winter heating and piping
it to the summer well and vice versa for summer cooling.

If youo have the ability to use an open loop gethermal well system you will save money


What ever you DO NOT I REPEAT DO NOT get suckered into using a geothermal loop system using
thermally enhanced grout as it is thermal clay- it holds heat and does not shed it and If a well driller tells you it does
you better check for a hand on your wallet.

if you do it this way:

Tell them you want to use mason sand and protect the pipe with a simple heavy plastic wrap from  black plastic tarp

AND DO NOT EXCEPT NO FOR AN ANSWER AS THEY CAN PUMP MASON SAND THROUGH THIER GROUT PUMPS.


A drilled geothermal well with thermally enhanced grout will be up to 400 feet deep with a loop of
poly pipe sunk all the way to the bottom

If you have a lot of land you wil be better off doing it with a shallow depth loop of X feet as you can buy
one solid roll and bury it in a foot of sand at the four to five foot depth in one piece from the geothermal
hot air handler which will double as an air conditioner if it is added.

Thermally welded poly pipe has leaked in the past and they have improved the pipe but..............................
if you have a leak you will damage the system$$$$$$$$$$$$$$$$$$$$$$ if you are not aware of it.


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## flyingcow (Jan 24, 2014)

I'm gonna jump in for a quick question. Burying it 5 ft? Is this depth ok for the up north crowd? We get an open winter and the frost can go deep.

BTW, good info Leon. Good to hear from someone in the business. 

Play With Fire- You looked at air sourced HP's? On the back of the envelope figuring my Mitsu HP costs about the same to operate as my gasser. Until you get into sub zero territory. My Kwh is 14.7 cents an hour.


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## MarkW (Jan 24, 2014)

How viable is GT using a pond rather than a ground loop?  I've got a large pond immediately adjacent to the house.  13' deep and temps going to be a good bit different than ambient air temps.  It would sure be a lot easier than burying it.


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## maple1 (Jan 24, 2014)

Ponds do get used in the right circumstances - yours sounds like it might be a candidate. Best to get a local Geo expert to check it out.

I also considered Geo before I redid my system. I was looking at 20k minimum for the Geo side - but with my baseboard I would have had to retrofit distribution of some sort to get the heat into my house. Maybe another 5-10k for that. So maybe total of 30k investment. But I really don't like ductwork & forced air, so not sure exactly where that would have went - but retrofitting a heat distribution system into a finished two-storey definitely would have its challenges. Then, I was getting mixed stories from others in the area who had put Geo in, on exactly how much their power bills went up. Anywhere from 'not much at all', to several hundred dollars per month in the winter. So I was looking at something like another $1-200/month in operating costs - likely on the conservative side. When I compared that to $12k for the way I did go (I underestimated that a bit when all was said & done), and no monthly operating cost for fuel for as long as I was able to do the wood - well, I went the way I did. I think we are actually using less electricity now than before even with an electric hot water heater heating DHW for 2 months of the summer, due to not having an oil burner running.

You also have to factor in other preferences & priorities that only you can asses an importance to - for me, I like everything about going to the woods, and 'doing the wood up'. And a lot of the year it's the only exercise I get - I think I'd go a little stir crazy if I had to stop. I am also lucky to have free reign to scrounge what I need, more or less from my back door - another factor. Even at that, I don't really spend all that much time at it in a year - nowhere near hundreds of hours in stacking.


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## PlayWithFire (Jan 24, 2014)

flyingcow said:


> Play With Fire- You looked at air sourced HP's?



I looked at heat pumps (HP) last year. I never compared the operating cost to wood, but I did know it was fairly efficient. Good to know that HP is costing you about the same as wood. GT is basically the same as a HP, except it uses the consent 55 deg ground to make it even more efficient.



MarkW said:


> How viable is GT using a pond rather than a ground loop?



I've seen some install options and it seems that a good size pond is just as good. Not sure on the exact details, but seems that all that water would be better at transferring heat then the ground.


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## PassionForFire&Water (Jan 24, 2014)

PlayWithFire said:


> At $160/cord (my current price) and $0.14/KWH (generation+transmission).  The estimated cost of running a geothermal system is nearly identical to a wood boiler, maybe even less.
> http://www.vermontgeo.com/geothermal_operating_costs.html
> 
> The install cost of geothermal with ducked work might be around $25k after 30% Gov rebates. The cost of wood boiler is probably about $15k.  Geothermal adds about $14k to the resale of a home.  Wood Boiler doesn't add anything to the resale of a home and may be seen as a negative (source: my real estate agent).
> ...



What is your heat distribution system ?
If it is baseboard that requires 180-185F water, then most likely the heat pump is not gone cut it.
In floor heating that requires only 90 to 120F water, the heat pump probably will do a nice and efficient job.


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## Floydian (Jan 24, 2014)

Hi PlayWithFire,

To make any kind of recommendation we really need more info. 

Do you know your heat load in Btus/hour OR your annual heat load in MM Btus?. If you don't know these numbers than figuring them out is step one regardless of whether you go GSHP, ASHP, or wood boiler. Once you have these numbers you can start figuring out your cost to operate based on COP's of the heat pump options or how many cords with the wood boiler.

What is your current heat distribution system?(forced air, hydronic baseboards, Cast iron radiators, radiant floors,etc.....) 

How large is your house and does it have a fairly open floor plan?

Depending on the heat load, I would recommend getting a quote on several Mini Split HPs just to compare vs the GSHP. COP's will be very close with GSHP vs the better MSHP's when you figure in the pumping costs of GS and several MSHP's *could* price at almost half your GSHP price.

Good luck,
Noah


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## Floydian (Jan 24, 2014)

This is also food for thought: http://www.greenbuildingadvisor.com...000-would-you-buy-pv-or-improve-your-envelope

Noah


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## leon (Jan 24, 2014)

flyingcow said:


> I'm gonna jump in for a quick question. Burying it 5 ft? Is this depth ok for the up north crowd? We get an open winter and the frost can go deep.
> 
> BTW, good info Leon. Good to hear from someone in the business.
> 
> Play With Fire- You looked at air sourced HP's? On the back of the envelope figuring my Mitsu HP costs about the same to operate as my gasser. Until you get into sub zero territory. My Kwh is 14.7 cents an hour.


 

========================================================================================================

Good Morning Flyingcow,

If you can go deeper AND you have the room;

the contractor must use a trench box 

The pipe should be wrapped in heavy plastic to protect it.

if you can arrange to have a trailer load or two of mason sand to bed
the tubing in all the better as you need to protect the line going
out and coming in.

The geothermal units have used either : 

anti freeze/preferrably the safe non toxic antifreeze 
glycol
alcohol
water
as heat conducting mediums,


The worry about bury depth is always cave in of the trench.

AND PROPER INSTALLATION:

IF YOU REALLY FUSS OVER THE INSTALLATION AND AVOID HEAT SPLICING the pipe runs in and out
you will have no problems with the installation


if you have the room the excavator will parallel the trench with the excavator
and dig a sloping trench wall to the final depth and the poly pipe is hand buried 
by the trench wall-getting rid of the big rocks and the sharp ones!

OTHERWISE:


When your contractor digs a trench;

they need to have a trench box or the aluminun trench box on wheels
that rides along the top of the trench while the pipe is installed-
passed through the rolling trench box as the person shoveling
is anchoring the pipe against the trench wall.


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## leon (Jan 24, 2014)

MarkW said:


> How viable is GT using a pond rather than a ground loop?  I've got a large pond immediately adjacent to the house.  13' deep and temps going to be a good bit different than ambient air temps.  It would sure be a lot easier than burying it.


 

You can use your pond very easliy by using a pipe loops that are spiralled and tied to together.

If you remember what a spirograph is or ever played with one with pencil and paper to make
loops you secure the pipe loops together with black tie wraps and weigh it down with concrete blocks


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## jeffesonm (Jan 24, 2014)

If you truly get get 90% of your heat from the insert now, I would consider investing ~$5K in a mini split to make up the other 10% vs investing $20K+ in anything.


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## AK13 (Jan 24, 2014)

Floydian said:


> What is your current heat distribution system?(forced air, hydronic baseboards, Cast iron radiators, radiant floors,etc.....)
> 
> Depending on the heat load, I would recommend getting a quote on several Mini Split HPs just to compare vs the GSHP. COP's will be very close with GSHP vs the better MSHP's when you figure in the pumping costs of GS and several MSHP's *could* price at almost half your GSHP price.



This is great advice here. I'd go with ASHP's over GSHP any day of the week. Similar efficiency. Less upfront cost (even once the 30% GSHP rebate is factored in). The only question is existing distribution system. If you have baseboard then maybe a biomass boiler (bulk-fed pellets or wood) would make sense. 

The other question is A/C. The ASHP's will give you an A/C system and the biomass will not. The GSHP system will provide A/C as well, but only if you are using water to air units, not if you are using water to water and planning to run it through a radiant floor or something.


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## MarkW (Jan 24, 2014)

leon said:


> You can use your pond very easliy by using a pipe loops that are spiralled and tied to together.


 This is what I suspected.  I'll have to get a GT evaluation to see exactly what's involved.  Thanks


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## slowzuki (Jan 24, 2014)

Just to be clear they are not similar efficiency.  Under average conditions, the ground source is about 2x as efficient.  In very cold weather that grows to maybe times more efficient depending how cold your field  gets.


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## heaterman (Jan 24, 2014)

We do all of the above. Each has its advantages but the biggest differences I see and what my customers see are these:

Installed cost: Advantage wood or pellets

Repair costs: Advantage wood or pellets.... although some repairs can be quite expensive with wood boilers, you will find a typical repair on a Geo system will hit 4 figures with monotonous consistentcy. Compressors/circuit boards/plugged heat exchangers etc can provide a very scary repair bill      to the point where one or two of them over the life of the system completely negate any and all savings delivered.

Operating costs: Advantage wood or pellets _but only if you consider your time and labor to be worth nothing _and you do not tally expenses for chainsaws, splitters, truck tractor or trailer etc. If those are realistically included, then the geo system will beat the wood system every time.

Reliability of the system: Advantage geo.....HUGE CAVEAT.....if it is sized and installed correctly.  If not, it will haunt you until it's abandoned. We've run into several whose use has been discontinued because the system was designed to a price point instead of being realistically set up for the job at hand.. While wood burning equipment itself is pretty reliable it is totally dependent on the "user" part of the equation and that will typically be the weak link in the chain.

Last but certainly not least.....what you buy any of these systems for.....*COMFORT!!* 
A forced air geo system that is sized right will keep you home at 70* no problem. However, customers routinely complain about the volume of air flow and the low temperature discharge air from registers. A geo system by its very nature works with much slimmer T than a typical forced air system. Air leaving the registers can be as low as 90-100 instead of 135+ and this contributes to an overall cool feel in the house. The same btu's are being provided but they will definitely feel different. There is no getting around it. If you can tie a ground source geo into a low temp radiant slab, then you have the comfort end of things by the short hairs. A geo will provide the same comfort level and mean radiant temperature as any other radiant system.
So for this one.....the most important one to me.....the advantage is definitely with wood. 
It gives you far more options for heat emitters and will provide a greater level of comfort in every application but a low temp radiant floor.


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## cookiemonster (Jan 24, 2014)

PlayWithFire said:


> At $160/cord (my current price) and $0.14/KWH (generation+transmission).  The estimated cost of running a geothermal system is nearly identical to a wood boiler, maybe even less.
> http://www.vermontgeo.com/geothermal_operating_costs.html
> 
> The install cost of geothermal with ducked work might be around $25k after 30% Gov rebates. The cost of wood boiler is probably about $15k.  Geothermal adds about $14k to the resale of a home.  Wood Boiler doesn't add anything to the resale of a home and may be seen as a negative (source: my real estate agent).
> ...





PlayWithFire said:


> At $160/cord (my current price) and $0.14/KWH (generation+transmission).  The estimated cost of running a geothermal system is nearly identical to a wood boiler, maybe even less.
> http://www.vermontgeo.com/geothermal_operating_costs.html
> 
> The install cost of geothermal with ducked work might be around $25k after 30% Gov rebates. The cost of wood boiler is probably about $15k.  Geothermal adds about $14k to the resale of a home.  Wood Boiler doesn't add anything to the resale of a home and may be seen as a negative (source: my real estate agent).
> ...




Hey "PWF". I have a Harman SF-360 and I love it. Reasons are many. Its a wood/coal combo unit. I heat with hot water all around. Radiant,baseboard, ect. I spent the first few years splitting a stacking wood and that got old quick. I've been burning premium anthracite for the last 3 yrs. and I am really enjoying it. I built a bin that hold 6 tons of coal. 6'x10'x5'. MUCH longer burn cycles. More even heat. No creosote. I get coal trucked in for $1200.00 for 5 tons. That lasts me from Nov. to March. I save about $2000.00 a winter with coal. Im in NY about an hour south of Albany.


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## __dan (Jan 24, 2014)

PlayWithFire said:


> At $160/cord (my current price) and $0.14/KWH (generation+transmission).  The estimated cost of running a geothermal system is nearly identical to a wood boiler, maybe even less.
> http://www.vermontgeo.com/geothermal_operating_costs.html
> 
> The install cost of geothermal with ducked work might be around $25k after 30% Gov rebates. The cost of wood boiler is probably about $15k.  Geothermal adds about $14k to the resale of a home.  Wood Boiler doesn't add anything to the resale of a home and may be seen as a negative (source: my real estate agent).
> ...



If you're paying for cordwood, I would say a pellet boiler, one of the European high quality boilers, is the go to solution to get off oil.

There are a number of advantages. The pellet boiler should be able to qualify as an automatic central heat source so you don't need a parallel backup system, which is a big savings on the install cost. The pellet boiler will have much better efficiency at part load, for DHW in the summer, and probably no storage tank required which is another big savings at installation. Fuel availability, handling, and standardization is much better compared to cordwood. Pellets you can get truck delivered, palletized, with the delivery truck having a motorized pallet handler to put them in the garage.

Saving the cost of the storage tank and parallel tie in to an alternate boiler, I would guess the install cost of the pellet boiler could be less than the cordwood gasifier and much less than GSHP. Expected lifetime of the major components for GSHP is 15 years. A high quality boiler could be double that without replacement of the major components.


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## PlayWithFire (Jan 25, 2014)

PassionForFire&Water said:


> What is your heat distribution system


Baseboard.  I was told that duct work would need to be added.  Which was included in the cost of the install.



Floydian said:


> To make any kind of recommendation we really need more info.


I know last year (before my using my insert) I burned 800 gallons of oil Oct – April. My house is about 2100 sq/ft.  It's semi open on the first floor with 3 bed rooms on the second floor.



jeffesonm said:


> If you truly get get 90% of your heat from the insert now, I would consider investing ~$5K in a mini split to make up the other 10% vs investing $20K+ in anything.


Point well taken.  Would this be better then just using my current oil boiler to supplement?

Thanks for all the awesome feed back!  It's given me a lot to think about.


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## jebatty (Jan 26, 2014)

There simply is no one best answer that fits everybody or every situation, except that insulation, sealing air leaks, and interior air quality works for everyone and has the greatest payback. HP technology is a great conservation improvement over resistance electric heat, and HP technology is improving. Kudos to everyone for doing their part in reducing use of fossil fuels, increasing energy efficiency, and contributing to a better world, whether or not intentional.

That said, I am reaching the point where solar electric may be the single best answer for a substantial area of the country. One time fixed cost, practically no maintenance, very long useful life, and freedom from dependence on energy markets controlled by others.


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## __dan (Jan 26, 2014)

I will add one more thing to what has already been said. It's the same thing I say to everyone in this situation and it really annoys me when the user will not make the first simple recommended step.

The first call is to the gas utility and ask them if gas is available in the street if if/when it may be available in the future. If gas (methane) is/will be available, it's a no brainer, go gas. With the fracking process, the US is said to have 200 years of domestic reserves and is predicted to become a net hydrocarbon exporter.

If no gas and no free cordwood, I would be looking at a high quality pellet boiler or building new a Passivhaus type, very low heat loss, nearly self heating structure.


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## PlayWithFire (Jan 26, 2014)

__dan said:


> The first call is to the gas utility


I agree.  Not only did I call the NG company, but I wrote up a flier touting the benefits of NG and spoke to everyone on my road that would open their door. Trying to get NG run down my road. But alas, even if the NG company had signed contacts with the whole road, it would not be “financially viable” for them to run lines down my road.


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## __dan (Jan 26, 2014)

PlayWithFire said:


> I agree.  Not only did I call the NG company, but I wrote up a flier touting the benefits of NG and spoke to everyone on my road that would open their door. Trying to get NG run down my road. But alas, even if the NG company had signed contacts with the whole road, it would not be “financially viable” for them to run lines down my road.


Good man. It could be a political issue also. Malloy, or whoever the current db in office is, is pro gas and wants to run lots of new pipeleines. I recall it being an issue in the news with the oil companies protesting his pro gas initiative.

You have a right to petition the government. The phone call is cheap if you want to call Malloy's office and say you have a petition for gas on your street and the utility is unresponsive. As a regulated monopoly, the gas utility could have obligations beyond serving only those they want to.

There will also be those within the gas company who think work is good and more is better.

Most people will not be able to go to a high end wood gasification or pellet boiler solution because of the high installation cost. If they want to be warm in the winter, gas boilers, methane, is the what they need.


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## Hansson (Jan 27, 2014)

Over here geothermal is taking over the market. Not many people instal pellets/wood boiler. The market for the pellets boilers are like dead..
The newest heatpumps have a cop of 5. Good to have floorheat or big radiators as the cop gets lower when using higher tempetures to heat the house.


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## jebatty (Jan 27, 2014)

Geo-thermal, heat pumps, and sustainable electric generation, combined with a much higher level of conservation and high energy efficiency appliances and lighting, could be the best future that now is in achievable sight. Sweden, Hansson's country, is a leader in some of this, but also is a very high user of electricity per capita. 78% of Sweden's electricity comes from nuclear and hydro, and 30% of Sweden's total energy production comes from biofuels, primarily wood. Phase out of nuclear is problematical for Sweden, but policy looks to a phase out. Sweden is not a leader in wind and solar electric but movement also is in that direction.

On a micro or home level, what is the possibility of solar electric, geo-thermal and heat pumps, to supply space heating, even in very cold areas of the US, like Minnesota? My solar electric has produced an average of nearly 11kwh/day since going active on Oct 28, 2013. Oct - Jan are low solar months in MN. Through our conservation measures, though,11 kwh/day now is exceeding our use of electricity for general purposes (not including dwh and heat). On most cloudy days we still produce more than 5 kwh. Conservation in electric use and higher energy efficiency lighting and appliances has resulted in just about a 50% drop in our general electric use, from about 20 to 10 kwh/day, and we are looking for ways to reduce that further. Our average use of electricity for dhw is about 3 kwh/day, and as solar ramps up with higher solar production months lying ahead, our solar electric easily will provide enough power for dhw plus excess. That leaves heat.

Right now about 85% of our heat comes from wood, the 15% balance is electric resistance to keep the basement at about 50F during the winter and backup for the house when we are gone. That 15% is about equivalent in energy to 1-2 cords of low heat value wood, like aspen, or about 3/4 to 1 cord of wood like oak. 

Using my estimated total annual solar production at about 9000 kwh, and assuming 13 kwh/day for general electric plus dhw (4750 kwh), I will have excess electric generation on average of about 4,250 kwh. That equals 14,500,000 btu's, or about the btu energy in one cord of aspen. If that excess electricity through heat pumps and geo-thermal and with a COP of 5 could be used to also provide heat year-round, but especially in winter, then our total household energy use would be 100% sustainable without use of wood. Maybe even some some excess electricity to charge a future electric vehicle. 

What's the thinking on this? Feasible to store sufficient geo-thermal heat pump produced hot water during daytime electric production to make it through the night or cloudy period? Other ideas?


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## peakbagger (Jan 27, 2014)

_What's the thinking on this? Feasible to store sufficient geo-thermal heat pump produced hot water during daytime electric production to make it through the night or cloudy period? Other ideas?
_
Probably not a good option to store geothermal produced hot warm water as geothermal heat is generally relatively low temperature, thus the storage needs to be huge. As long as net metering remains available it is the way to go but as non dispatchable renewables like solar increase as a proportion of the grid, I fear that it is going to be chipped away by the utilities. At some point real time pricing is going to appear which will shift a portion of the burden for high heating season power demand into the consumers laps and I expect even the folks will net metering will be clipped by that shift.

Ultimately the best investment is energy reduction. Spend the money to build a net zero energy house and on the rare times you do need heat, run a small woodstove. Unfortunately, most folks want to keep their current home so the net zero house is unlikely although deep retrofitting of a current house can substantially reduce usage.

Off gridders in northern climates have already worked out solutions to this and generally it entails wood heat, solar panels, a battery bank good for three days, a back up generator and a willingness to change their lifestyle to adjust to low energy use.


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## moey (Jan 27, 2014)

We have a ground loop about 3200ft about 5 foot deep in the ground 5 ton system in mid maine ( colder then where you are ) about 2400sq ft house. This is our first winter it has done very well in the cold. Last month my kw usage was about 2600kw before the system it was around 900kw per month. So about 1700kw $238 per month for heat last month. Ping me if you have some questions Ive learned a lot since we got it.

I question any heating system adding value to a house it may sell a house faster but adding value in my opinion just isnt there but what do I know.

Ductwork isnt included in the 30% credit there was a recent IRS ruling 2 months ago excluding it.


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## jebatty (Jan 27, 2014)

Energy reduction has been our focus and change in life style in addition to simple reduced usage is our direction. Looking at past electric bills, before our big effort to reduce usage, Nov and Dec electric usage for general service historically was about 600 kwh/mo. For Nov and Dec 2013 the usage was 350 kwh/mo. Beginning in Jan 2014 we switched our lighting to nearly all LED, so I expect a further reduction. The reductions so far have been no more radical than shutting things off when not being used or needed. Reductions beyond this likely will entail a change in lifestyle and the thinking has started as to what to change.


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## Karl_northwind (Jan 27, 2014)

Hansson said:


> Over here geothermal is taking over the market. Not many people instal pellets/wood boiler. The market for the pellets boilers are like dead..
> The newest heatpumps have a cop of 5. Good to have floorheat or big radiators as the cop gets lower when using higher tempetures to heat the house.



in Sweden this fall that is what I saw, and was told.  There are some interesting problems that the utilities are encountering with large amounts of solar electric in the summer and large amounts of geo heat in the winter.   My wife's cousin is an engineer with one of the utilities up north (Karlstad) That said, the geo units I saw in all sorts of places (including the old family homestead) were way more advanced looking than the clunky stuff I see around here.  Compare looking at a european Mod-con versus an atmospheric gas boiler.  that kind of comparison. 

the availability of 3 phase power everywhere and low-carbon electricity (lots of hydro from Norway) makes that option a lot less ugly to me.


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## Hansson (Aug 20, 2014)

Dont u have 3 phase power in the US?


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## peakbagger (Aug 20, 2014)

Hansson said:


> Dont u have 3 phase power in the US?



Three phase is generally not available for residential homes and rural areas in the US and generally when it is available it is priced as a commercial account. Thus most folks have to live with single phase. This makes it difficult to run industrial equipment in residential area and there is market for converters that convert single phase to three phase. Inverter type motors generally can accept single phase input but the given the scarcity of three phase residential equipment is rarely offered as three phase. Generally commercial equipment can be had in either single or three phase in the smaller units and then switch to three phase for the larger units.


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## Karl_northwind (Aug 20, 2014)

I need to get a convertor, we just got our first piece of 3-phase equipment, a food processor of all things!


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## arbutus (Aug 20, 2014)

AK13 said:


> This is great advice here. I'd go with ASHP's over GSHP any day of the week. Similar efficiency. Less upfront cost (even once the 30% GSHP rebate is factored in). The only question is existing distribution system. If you have baseboard then maybe a biomass boiler (bulk-fed pellets or wood) would make sense.
> 
> The other question is A/C. The ASHP's will give you an A/C system and the biomass will not. The GSHP system will provide A/C as well, but only if you are using water to air units, not if you are using water to water and planning to run it through a radiant floor or something.


 

ASHP if you need air conditioning at all.  Modern units appear to have good performance down into the teens.
Here in Michigan's UP we do not need AC, and spent a LOT of time last winter well below zero.  I looked into GSHP and needed something like 22 gpm water in an open loop water to water system on a design day - No thanks!


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## AK13 (Aug 29, 2014)

slowzuki said:


> Just to be clear they are not similar efficiency.  Under average conditions, the ground source is about 2x as efficient.  In very cold weather that grows to maybe times more efficient depending how cold your field  gets.



I disagree. Although it could depend on your definition of similar. Modern ASHP's are providing AVERAGE annual COP's on the order of 2.5. Obviously this is ENTIRELY dependent on where you live. So my value is for the Northeast. Up in NB, perhaps this drops to 2.0 to 2.25 range. But the OP is in CT where the temps are warmer and he'll be seeing a COP of 2.5 easily. I do not believe GSHP's are producing COP's of 5.0 plus. And even if the mfr's are making that claim if you do an honest analysis and include all of the pump energy, etc you'll find that the true COP takes a significant hit. Last time I did a thorough analysis we determined that the GSHP's COP for our closed loop application was about 0.5 to 1.0 COP higher than for the ASHP's. And we calculated that the better investment was in PV panels to make up this difference. 

Obviously, I'm not a big fan of GSHP's. They have their place, but they are costly, complicated and there are far more pitfalls to avoid. For example, one dirty little secret is that in a closed loop system the ground is not an infinite source of heat. Here in the northeast if you have a system that is used only in heating mode or very unbalanced with much more heat than cool you will actually cool the earth over several years. You need to "recharge" the ground in the summer by using A/C.


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## Hansson (Sep 9, 2014)

U dont need to recharge the ground. Do you think that u can do that whit a A/C?

The swedish energy agency have done a real test in 20 houses. The SCOP in the newer instalions is around 3

https://translate.google.se/transla...varmepumpar-matningar-i-hus/?tab=2&edit-text=


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## heaterman (Sep 9, 2014)

I haven't verified this but I was told just last Saturday that the largest Mitsubishi wholesaler in the state just dropped the line. From what the contractor was telling me they let it go because the inverter units did not perform as promised and Mits will not do anything about it. They have a LOT of unhappy customers.

I like ground source heat pumps for the way they perform but only in a closed loop vertical bore field. I heard of a couple people whose horizontal fields froze solid last winter. The system ran so much that it pulled frost right down to the elevation of the ground loops. At that point system performance plummeted and those poor fellas were running on electric backup.. $$$$$.$$

As Arbutus said the flow rate can get really high when we get temps like last winter. I quoted a house last year (McMansion) that had a max flow rate of 97GPM and the owner wanted to go pump n dump rather than closed loop. Didn't happen.

From what I have observed and heard from customers, the comfort level of the two systems is not comparable. Wood hands down.


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## jebatty (Sep 9, 2014)

This comparison is one of apples and oranges: different systems with different considerations. 

For me, with an ample supply of wood from our own property and the ability to harvest the wood for my gasifer and wood stove, plus being present between my wife and I to fuel each as needed, and not minding very minimal mess (grandchildren are messier than is the wood), wood wins over all alternative heat sources on comfort and cost. That said, a mini-split may be in the future for us if we can get an off-peak electric rate and where the mini-split can meet our heat demand down to about 20F or lower. That would eliminate much of the labor in C/S/S wood, which as I age becomes of more significance, and with our solar electric, the cost may be near $0 (although we would lose credits that otherwise would be convertible to cash). I doubt geothermal ever would be a consideration for us.

For a person who wants a fully automated system, who must pay high prices for wood, who cannot be around to fuel the wood appliance as needed, who will not accept minimal smoke and mess, and who is in a climate where a HP geothermal is in its sweet spot, I can fully understand the interest in geothermal.

This discussion is good, in large part because it leads to a more complete appreciation of the pros and cons of two types of heating system.


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## goosegunner (Sep 9, 2014)

My cousin has a very elaborate and expensive horizontal loop Geo system. First year would not keep up. Added another field. It will heat down to about 15 degrees after that the house starts losing temp. For many weeks this past winter it would maintain his house from 55 to 60 degrees. He refused to use propane so he slept with many layers and stocking cap.

His heat emitters are all low temp in floor,  gypcrete on the upper levels.


One of our new Fire station's has a geo pond loop. There is no back up system. You basically freeze your ass off a lot. Depth of winter the glycol loops coming back were 27 degrees.

I will stick to my wood boiler.

gg


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## Karl_northwind (Sep 15, 2014)

Nothing makes heat like burnin' stuff.


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