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  #1  
Old 03-23-2011, 11:13 AM
cmosdes cmosdes is online now
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Heat Pump vs Gas Furnance and AC

It looks like my 20 year old gas furnace is in need of some serious repair, so I need to consider purchasing a new unit.

We don't have central AC right now and while we really only need it about 12 to 14 days out of the year, it certainly would be nice to have on those days.

I'm trying to decide if I should go with a heat pump with gas furnace backup or go with a high efficiency gas furnace with an AC unit.

I'm in the pacific NW and our temps are usually pretty temperate. We get maybe 15 days or so below 30 and as I said above, 12 to 14 days in the high 90s. Seems like a good range for a heat pump, but what I've read about heat pumps is giving me serious second thoughts. First, it sounds like they don't give out a "warm" heat like a gas furnace. Second, they can cause a big mushy mess around them due to the defrost cycle. Finally, they don't tend to last as long.

So anyone have any experience with heat pumps or are there any contractors around here that can offer up some advice?
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  #2  
Old 03-23-2011, 11:20 AM
Khendrask Khendrask is offline
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Down here in SC heat pumps are pretty much the only show in town. I've had a Lennox in my house for the past 12 years with no problems. (Carrier before that which died at 14 years old or so).

Cooling cost is not bad, moderate day heating cost isn't bad. Sub freezing heating costs are pretty high due to running the electric strips in the outdoor unit.

The only thing annoying is the sound the compressor unit makes when it cycles the reversing valve. I'd advise keeping it away from your master bedroom window!
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  #3  
Old 03-23-2011, 11:45 AM
awldune awldune is offline
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Originally Posted by cmosdes View Post
First, it sounds like they don't give out a "warm" heat like a gas furnace. Second, they can cause a big mushy mess around them due to the defrost cycle.
The first is definitely true. A heat pump on a cold day is going to be putting out air that is warmer than your thermostat setting, but not by much. Not something to warm your hands by when you come in from the cold.

I have never, ever heard of the "mushy mess" problem here in the southeast. Stands to reason it would be more of an issue in the PNW. Often a heat pump is installed on a concrete slab, so it seems like this problem could be addressed by a larger slab.
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Old 03-23-2011, 11:51 AM
Dag Otto Dag Otto is offline
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Originally Posted by cmosdes View Post
We don't have central AC right now and while we really only need it about 12 to 14 days out of the year, it certainly would be nice to have on those days.

I'm trying to decide if I should go with a heat pump with gas furnace backup or go with a high efficiency gas furnace with an AC unit.
I'd consider the heat pump with gas furnace backup for a couple of reasons: First, the emgency source of energy on really cold days is gas and not electric resistance heating. Second would be the duty cycle of the refrigeration equipment - the heat pump would be working quite often, while an AC only unit would be used for 12-14 days and then sit idle for the rest of the year. Having equipment sitting idle for so long probably isn't good.

Last edited by Dag Otto; 03-23-2011 at 11:52 AM..
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  #5  
Old 03-23-2011, 12:00 PM
raindog raindog is offline
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The question[s] that must be answered (and can only be answered by you) are:

1) What is your primary objective? Towards that answer rate the following in order of importance:

Your carbon footprint. IOW, the ecology.

Your desire for A/C.

Your desire for "hot" heat.
Both a heat pump or furnace will easily keep your house at the temp you set it at. But as noted by another poster, gas puts out higher discharge air temps at the register (100-125) vs a heat pump (90-110)

The lowest possible utility bills.

The lowest possible "first cost"; the initial cost of installation.

How long you need the system to last.
And this is generally a way of asking how long you intend to live there.
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  #6  
Old 03-23-2011, 12:26 PM
cmosdes cmosdes is online now
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Originally Posted by raindog View Post
The question[s] that must be answered (and can only be answered by you) are:

1) What is your primary objective? Towards that answer rate the following in order of importance:

Your carbon footprint. IOW, the ecology.

Your desire for A/C.

Your desire for "hot" heat.
Both a heat pump or furnace will easily keep your house at the temp you set it at. But as noted by another poster, gas puts out higher discharge air temps at the register (100-125) vs a heat pump (90-110)

The lowest possible utility bills.

The lowest possible "first cost"; the initial cost of installation.

How long you need the system to last.
And this is generally a way of asking how long you intend to live there.
Carbon footprint? I'm not overly concerned about it in this case. It wouldn't be a deciding factor.

I would like cooling (whether by AC or heat pump doesn't really matter), but it isn't a must. At this point it seems economical to do because the cost of adding it to a furnace replacement is small compared to adding it on its own.

Hot Heat - I want to feel comfortable in the winters. This is my biggest fear with the heat pump. Will the house feel chilly with a heat pump?

Utility bills are a concern, but not an overriding one. The advantage of having a heat pump with a furnace is that I can switch between gas and electric if one or the other gets prohibitively expensive. Right now my gas bill is about $200/month in the winter. Not bad, so I don't really need to cut costs all that much.

The cost of installation is about the same, so that isn't a factor.

I'm hoping to be in this house a very long time (10+ years).


I'd go with a heat pump if I knew what a "not warm" heat really meant and if I thought the heat pump would last 20 years. I'm not sure of either of those.
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  #7  
Old 03-23-2011, 01:04 PM
Magiver Magiver is online now
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If you're on well water then you should consider geo-thermal because you already have one well drilled. It would also provide hot water. You wouldn't need to keep a gas hookup because auxiliary heat would be electric.
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  #8  
Old 03-23-2011, 01:55 PM
raindog raindog is offline
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Originally Posted by cmosdes View Post
Carbon footprint? I'm not overly concerned about it in this case. It wouldn't be a deciding factor.

I would like cooling (whether by AC or heat pump doesn't really matter), but it isn't a must. At this point it seems economical to do because the cost of adding it to a furnace replacement is small compared to adding it on its own.

Hot Heat - I want to feel comfortable in the winters. This is my biggest fear with the heat pump. Will the house feel chilly with a heat pump?

Utility bills are a concern, but not an overriding one. The advantage of having a heat pump with a furnace is that I can switch between gas and electric if one or the other gets prohibitively expensive. Right now my gas bill is about $200/month in the winter. Not bad, so I don't really need to cut costs all that much.

The cost of installation is about the same, so that isn't a factor.

I'm hoping to be in this house a very long time (10+ years).


I'd go with a heat pump if I knew what a "not warm" heat really meant and if I thought the heat pump would last 20 years. I'm not sure of either of those.
Based on what you're saying, and given the fact that you live in a temperate climate, I'd recommend a 13 SEER HP or A/C, coupled with a 80% NG furnace, and heres why:

1) A heat pump will produce a BTU cheaper than even a high efficiency gas furnace. However, it doesn't appear that current utility costs are a concern.

2) The "payback"; the period of time it takes to get your money back from a high efficiency system is much longer in moderate climates, and thats logical; if the unit isn't seeing much run time to begin with, its going to take a long time to recoup the extra investment of a high efficiency system. There are roughly 2 things that will influence run time: The weather, which you can't control, and Your lifestyle, which is essentially whether you use a setback stat and what temperature settings you use when at home. I forgot to ask you lifestyle questions, but considering you are not overly concerned about the environment , or your utility costs------coupled with the moderate climate------suggests that you don't need a super-duper high efficiency unit.

3) My anecdotal experience is that the average A/C system lasts 15-20 years. The average HP 12-15 years. (keep in mind it sees both summer and winter duty) The average furnace 20-25 years.

4) Nobody says you have to use the heat pump for heat if you have a heat pump installed with a NG furnace backup. It is easy and seamless (via the stat) to simply use the furnace and A/C. IOW, you can always treat it as a furnace and A/C system and essentially ignore the HP function in the winter.

The reasons you might want to have a HP put in: 1) Flexibility of a dual heating source, and, 2) They are cheaper per BTU than a gas furnace.

The reasons you might not want a HP: 1) The heat won't be as hot in the winter, and it seems that that is a concern. (see above for temps), and, 2) the cost for the HP will be $1000> more than an equivalent A/C system.

It would seem that comfort and flexibility are the bigger concerns. All things considered, a NG furnace, coupled with an A/C or HP is what you might need.

I'd suggest getting some numbers from contractors.
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  #9  
Old 03-23-2011, 01:56 PM
raindog raindog is offline
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Originally Posted by Magiver View Post
If you're on well water then you should consider geo-thermal because you already have one well drilled. It would also provide hot water. You wouldn't need to keep a gas hookup because auxiliary heat would be electric.
I suppose some caution might be in order as I've seen wells run dry on simple pass through systems. (pump and dump) And given the moderate climate the paybacks might be purdy long.
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  #10  
Old 03-23-2011, 02:03 PM
raindog raindog is offline
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ETA
With a HP your home won't be chilly, but you may perceive it to be chilly based on what you're coming from. That is may.

If you set your stat to 70, it will be 70, the same as gas.

But if you're coming from a "hot" heat like NG, LP or Oil, a heat pump may feel like the air isn't hot.

Thats because it is cooler than your previous heating system (NG) and 95 is cooler than your body temp.

Many/most acclimate well and do fine. Others can't be made to like it and remain semi-unhappy.

YMMV
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  #11  
Old 03-23-2011, 02:08 PM
raindog raindog is offline
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ETA
It is possible that a HP in the NW will last 20 years. The anecdotal lifespans I gave earlier were for units in the Midwest which will see much longer run times year after year.

So YMMV. I'd ask a contractor about lifespans of units in the NW. My gut tells me 'no', but who knows....

Last edited by raindog; 03-23-2011 at 02:08 PM..
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  #12  
Old 03-23-2011, 02:15 PM
Magiver Magiver is online now
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Originally Posted by raindog View Post
I suppose some caution might be in order as I've seen wells run dry on simple pass through systems. (pump and dump) And given the moderate climate the paybacks might be purdy long.
I don't know if new houses are that much more efficient but I know someone who went from gas to geo-thermal (with the building of a new home) and his energy costs went down significantly despite a huge increase in square footage. He went from a 4 bedroom ranch to a McMansion. 25 deg winters and 90 deg summers. Not sure if that is a moderate climate.
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Old 03-23-2011, 02:20 PM
raindog raindog is offline
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I don't know if new houses are that much more efficient but I know someone who went from gas to geo-thermal (with the building of a new home) and his energy costs went down significantly despite a huge increase in square footage. He went from a 4 bedroom ranch to a McMansion. 25 deg winters and 90 deg summers. Not sure if that is a moderate climate.
We install geos and that has been our experience as well. Geos are a good thing for the environment and for the homeowner.

The only drawback is that they can be expensive------expensive enough that it might make it hard to make sense of the additional investment in moderate climates.

We've had people make the investment because of social concerns. (often they're also driving hybrid cars)

But if the OP has no large social concern and if economics are sole criteria, it may be harder to make sense of it.
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Old 03-23-2011, 02:29 PM
Balthisar Balthisar is offline
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I have a ground source heat pump, and one of its most obvious benefits over the gas system it replaced (and gas systems in other places I've lived) is this: it doesn't pump out hot air. Instead, has runs for much longer cycles using air that's just slightly warmer than the target temperature. This results in a house that's always comfortable without hot spots, without cold spots, and without any cycles of being warmer or chillier. In fact, this operation is very similar to a very high efficiency gas furnace, which also don't pump out very hot air.

I don't have any problems with condensation puddling anywhere.

The big question will be your ROI. In Michigan I obviously use it all the time during the winter, but I also use it all the time during the summer. Without the air conditioning, even during a cool 75 degree day, the house will become hotter than that.

Forgot to mention… the auxiliary system (not a backup) is resistance heat. It only rarely kicks on during extremely cold days, and doesn't contribute too much to additional energy costs.

Having the ground source system also gives me moral permission to drive my Expedition whenever the feeling strikes me.
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Old 03-23-2011, 02:37 PM
cmosdes cmosdes is online now
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Thanks, raindog. Your suggestions are very welcome.

There is no doubt I'll be putting in a NG furnace. My only question was whether to go with a high efficiency one (92%) and AC or go with a low efficiency one with a HP. It sounds like you'd recommend the HP and lower efficiency NG furnance over an AC unit and high efficiency furnace.
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Old 03-23-2011, 03:24 PM
raindog raindog is offline
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Originally Posted by cmosdes View Post
Thanks, raindog. Your suggestions are very welcome.

There is no doubt I'll be putting in a NG furnace. My only question was whether to go with a high efficiency one (92%) and AC or go with a low efficiency one with a HP. It sounds like you'd recommend the HP and lower efficiency NG furnance over an AC unit and high efficiency furnace.
You're welcome!

The argument for an 80% furnace with a HP: Lower overall utility bills, and the flexibility of 2 heating sources.

The argument for 92% furnace and a A/C system: Nice warm heat. Great comfort.

However in the NW both systems should produce manageable utility bills. The A/C will be the same.

I might suggest having them price the best of both: a 92% (or more) NG furnace coupled with a HP.
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Old 03-23-2011, 03:52 PM
beowulff beowulff is online now
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Originally Posted by awldune View Post
The first is definitely true. A heat pump on a cold day is going to be putting out air that is warmer than your thermostat setting, but not by much. Not something to warm your hands by when you come in from the cold.
This was true on my old unit, but my SEER-16 unit I just installed puts out 105F+ air even with an outside temperature of 20F. I don't even have heat strips.
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Old 03-23-2011, 05:11 PM
cmosdes cmosdes is online now
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Originally Posted by raindog View Post
You're welcome!

The argument for an 80% furnace with a HP: Lower overall utility bills, and the flexibility of 2 heating sources.

The argument for 92% furnace and a A/C system: Nice warm heat. Great comfort.

However in the NW both systems should produce manageable utility bills. The A/C will be the same.

I might suggest having them price the best of both: a 92% (or more) NG furnace coupled with a HP.
That is exactly what I'm having them do. With the rebates for a heat pump the price was pretty similar to that of an AC. But, as I said, cost here isn't my biggest concern. I really want to be comfortable in the winter. We tend to keep the house at 66 to 68 in the winter and I'd hate to think we'll need to move that much higher to feel as warm with a heat pump.

Thanks to everyone else, too, for the inputs. I'll need to do a bit more research on the outputs of the various systems to see what makes the most sense.

Is there any particular brand I should stay away from? Any brand that stands out as being superior?
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Old 03-23-2011, 05:20 PM
TravisFromOR TravisFromOR is offline
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I'm not impressed with heat pumps.

I recommend a gas furnace and a swamp (evaporative) cooler. I have a swamp cooler--it's virtually free to operate in the summer.

Last edited by TravisFromOR; 03-23-2011 at 05:21 PM..
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Old 03-23-2011, 05:25 PM
raindog raindog is offline
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Originally Posted by cmosdes View Post
That is exactly what I'm having them do. With the rebates for a heat pump the price was pretty similar to that of an AC. But, as I said, cost here isn't my biggest concern. I really want to be comfortable in the winter. We tend to keep the house at 66 to 68 in the winter and I'd hate to think we'll need to move that much higher to feel as warm with a heat pump.

Thanks to everyone else, too, for the inputs. I'll need to do a bit more research on the outputs of the various systems to see what makes the most sense.

Is there any particular brand I should stay away from? Any brand that stands out as being superior?
Unlike cars----where a Chevy is always a Chevy, and if you want a substantially better car you buy a Buick or Cadillac---------each manufacturer has product line that starts with "builders models" up to top-of-the-line models, all under the same badge.

So a high end Goodman (a brand that has its share of critics) is a better unit than a builders model Carrier. (a brand thought to be a premier brand)

So, IMO, find the features you want, and the contractor you want/trust, and don't get wrapped around the axle over brand name.

Virtually every manufacturer IMO----including Goodman------has some excellent models in their product line.

The internet is full of Coke vs Pepsi type brand arguments, and they will drive you crazy. IMO/IME, you're at your best if concentrate on (in order)

1) The features you want/need. (which requires you to get educated)

2) A contractor who is top notch. (which requires you to be diligent)

3 The brand name on the appliance.
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  #21  
Old 03-23-2011, 05:49 PM
cmosdes cmosdes is online now
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Can anyone help me decipher this spreadsheet found here.

If you look at the section for "house load", I assume the 791.66667 number comes from his sq_ft, times the BTU/sq_ft/Deg F/Day and divided by 24. But I don't see where the numbers for the Heating Output HP (kBTU) and Heating Input Power HP (kW) come from. Heating Output Power HP (kW) is simply Heating Output HP (kBTU)/3.41. So right now I'm really stumped on the first two items. I'm hoping I can figure out the test if I knew where those are coming from. Anyone know?
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Old 03-23-2011, 05:50 PM
cmosdes cmosdes is online now
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Originally Posted by TravisFromOR View Post
I'm not impressed with heat pumps.

I recommend a gas furnace and a swamp (evaporative) cooler. I have a swamp cooler--it's virtually free to operate in the summer.
What is it about heat pumps you don't like?
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Old 03-23-2011, 07:21 PM
Magiver Magiver is online now
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Originally Posted by raindog View Post
We install geos and that has been our experience as well. Geos are a good thing for the environment and for the homeowner.

The only drawback is that they can be expensive------expensive enough that it might make it hard to make sense of the additional investment in moderate climates.

We've had people make the investment because of social concerns. (often they're also driving hybrid cars)

But if the OP has no large social concern and if economics are sole criteria, it may be harder to make sense of it.
Most of the cost seems to be in the well. Otherwise, it's just any other exchanger with a compressor unit. The rate of return is in relation to the sources of energy available.

I don't understand why the closed loop system uses antifreeze but I could certainly trench my hard for almost nothing to install the lines for it. That's got to be a lot cheaper than drilling a well.

I'm getting ready to help someone install a well type system. We already moved the exchanger. It was heavy as hell. It's the type with an electric backup heater for forced air.

Last edited by Magiver; 03-23-2011 at 07:24 PM..
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Old 03-23-2011, 08:57 PM
Balthisar Balthisar is offline
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My complete geo system was $4000 more than the average quotes from other companies' super-high efficient gas systems. I attribute that to the labor and materials involved in the ground loop, with a slight premium for a system that doesn't have the sales volumes of traditional systems. On the other hand I have a nice desuperheater described in another thread that's not part of traditional systems. And...

The power costs (i.e., consumption but not distribution) is at 50% because it's a "green" system. That means that all things being equal (they're better, in fact), my A/C operating costs are only half of what they were with the old HVAC system.

I didn't do it for any social concerns nor do I drive a hybrid; rather the ROI was fast and the long term savings were obvious (as I said, it makes me feel morally okay to drive what I want to drive). The ROI was key; it made perfect sense.
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Old 03-23-2011, 09:44 PM
Magiver Magiver is online now
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Originally Posted by Balthisar View Post
My complete geo system was $4000 more than the average quotes from other companies' super-high efficient gas systems. I attribute that to the labor and materials involved in the ground loop, with a slight premium for a system that doesn't have the sales volumes of traditional systems. On the other hand I have a nice desuperheater described in another thread that's not part of traditional systems. And...

The power costs (i.e., consumption but not distribution) is at 50% because it's a "green" system. That means that all things being equal (they're better, in fact), my A/C operating costs are only half of what they were with the old HVAC system.

I didn't do it for any social concerns nor do I drive a hybrid; rather the ROI was fast and the long term savings were obvious (as I said, it makes me feel morally okay to drive what I want to drive). The ROI was key; it made perfect sense.
Did the company that built it describe any difference in efficiency between a ground loop and a well system? Is the glycol anything special or was it automotive antifreeze? What was your ROI for the $4000 difference?

Last edited by Magiver; 03-23-2011 at 09:44 PM..
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Old 03-23-2011, 10:21 PM
China Guy China Guy is offline
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I'm in the PNW (Seattle Eastside) and interested in the conclusions of this thread as we're gonna build pretty soon.
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Old 03-23-2011, 11:02 PM
raindog raindog is offline
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For those who don't already know, I'm an HVAC contractor and sell and install geo systems.

It is largely true that difference in cost related to a geo is mostly caught up in the cost of the field. There are basically 3 types of "closed loop" systems. My cost for a field runs between $1500-2000 per ton. I don't mark up the field at all.

The HVAC part of the system is comparable to a high seer system, IOW, my costs for the geo system without the loop is comparable to the costs associated with an 18 seer system.

My profit margins are about the same. If not for the cost of the field/loop the cost of a geo would be comparable to an 18 seer air source heap pump.

By way of example, I'm installing a 3 ton geo next week, and the cost of the HVAC part of the system is around $12K, which is comparable to a high seer air source heat pump. But.......there will be an additional $6K for the ground loop. Sop the total cost to the homeowner will be roughly $18K
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Old 03-23-2011, 11:53 PM
Magiver Magiver is online now
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Originally Posted by raindog View Post
By way of example, I'm installing a 3 ton geo next week, and the cost of the HVAC part of the system is around $12K, which is comparable to a high seer air source heat pump. But.......there will be an additional $6K for the ground loop. Sop the total cost to the homeowner will be roughly $18K
what would be the cost savings per year for a 3 ton system versus a high efficiency system of similar size?

Last edited by Magiver; 03-23-2011 at 11:55 PM..
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  #29  
Old 03-24-2011, 09:15 AM
raindog raindog is offline
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what would be the cost savings per year for a 3 ton system versus a high efficiency system of similar size?
We haven't quite quantified that yet. Its something we're working on. The manufacturers we work with tell us that they have SEER ratings in the 30ish range, although I haven't seen any data yet. We hope to have a calculator on our web site within a year that allows a consumer to calculate operating costs and make vis a vis comparisons as well as ROI info.

Its worth noting that the legislation that allowed homeowners to take a $1500 direct tax credit for a variety of efficiency improvements (and was scaled way back as of 1/1/11) had an amazing exception for geothermal.

The legislation (as I understand it) for geo didn't semi-end in 2010, but runs through 2016. Even more, the tax credit didn't cap out at $1500. It was a tax credit for 30% of the installed prices with no limit. So a guy spending $18K on a geo was/is getting a $6k tax credit, which puts the final price close to the cost of an 18 SEER system.

That tax credit had the effect of converting high seer buyers to geo buyers.
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Old 03-24-2011, 09:42 AM
Balthisar Balthisar is offline
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Originally Posted by raindog View Post
By way of example, I'm installing a 3 ton geo next week, and the cost of the HVAC part of the system is around $12K, which is comparable to a high seer air source heat pump. But.......there will be an additional $6K for the ground loop. Sop the total cost to the homeowner will be roughly $18K
This is almost perfectly in line with all on my quotes from a few years ago, except as I said, my ground loop was only about $4K of the price. Mine was a 3.5 ton system, if I recall correctly.

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Did the company that built it describe any difference in efficiency between a ground loop and a well system? Is the glycol anything special or was it automotive antifreeze? What was your ROI for the $4000 difference?
I actually did all my research myself. The technical specs indicate thermal efficiencies based on the ground or well temperature. Wells are significantly more expensive, and I didn't see a reasonable return for the well. On the other hand, my back yard would still be more intact.

The complete ROI versus the original system was originally about nine years, but it's gotten stretched to 12 years due to so much time leaving the house vacant (i.e., the system running cold in the winter and hot in the summer when I'm on the road for months at a time). It can drop again (or go up) depending on natural gas price fluctuations. I didn't have enough reliable data on the return versus a high-efficiency gas system. The best I can figure is that I'd probably have saved 20% on natural gas consumption, but with no electrical discount for A/C use in the summer (not a "green" system).

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Originally Posted by raindog View Post
The legislation (as I understand it) for geo didn't semi-end in 2010, but runs through 2016. Even more, the tax credit didn't cap out at $1500. It was a tax credit for 30% of the installed prices with no limit. So a guy spending $18K on a geo was/is getting a $6k tax credit, which puts the final price close to the cost of an 18 SEER system.
I think I got a $500 credit the year of installation, and a $4000 deduction (not a credit) the year the installation was completed ("completed" meaning that the property was brought back up to standards, i.e., the grass over my loop field).
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  #31  
Old 03-25-2011, 09:56 AM
luvrbcs luvrbcs is offline
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Join Date: Nov 2008
We have both a high efficiency heat pump and high efficiency variable speed gas furnace. We are in Pittsburgh, PA. area. It works out great. The heat pump runs heat during the spring and fall with occasional bouts in the winter. If it still feels chilly we just set it on emergency heat and let the gas run.

Since we were upgrading our system, it was a no brainer (to us) that since we had the unit for A/C, why not use it for heat also. We lived in Maryland for the past 25 years so we are very experienced with heat pumps and feeling cold, but, they do work well on those not quite so cold days.

We average our utility bills so I don't know what the savings are, but we are satisfied.
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