Can Someone Explain Geo Thermal Heating To Me?

[jkeyser14]

I really don't believe that. Unless your geothermal system was <$3,000 installed.

Your geothermal system would basically have to use literally 0 electricity for the payback to be 7 years compared to an air-source heatpump.

Sounds like someone did the calculations against an old-school R22 heatpump that would be running with the aux resistance heat on most of the winter.

My geothermal system has a COP of 5.1 and an EER of 45. The heat pump was about $3k-$4k each more than a standard air source heat pump (two 3 ton systems), and the wells were $6k. The desuperheater was $1k.There was a $3k state grant and a 30% federal tax credit which applied to everything, including the ductwork since it was part of the system install.

 

[American Locomotive]

So with a COP of 5.1, and a $10k per unit higher install cost, you're looking at a payback of ~15-20 years compared to a modern split-system air-source heat pump (even factoring in the state grant). Compare it to a modern mini-split with Hyperheat (or equivalent), and you're looking at a payback of ~30-40 years....

Don't get me wrong, I'm not saying anything bad about your system, just that a payback of 7 years compared to a standard air-source heat-pump is REALLY stretching it. Basically those numbers would have to be done with like the worst air-source heat pump possible, in the absolute worst-case arctic winter, with your geothermal system locked at the lowest-stage at all times (since the efficiency drops way off at full load).

 

[yeldogt]

You never need an additional well for short periods. If your system was installed by an idiot and was undersized the electric backup heater would kick in on those days. But if you hire a competent contractor the well will be appropriately sized from the beginning.

That was my point ... the ability of the system to be able to handle the full load depends on the design. You live in MD .... what if your house was in ME ?

It can't have the same sized system given the different locations

A 5T in MD may not do it in ME .... so you either need a larger system or back-up. Electric backup w/o solar in most markets defeats everything.

It's all math .... house needs so many BTU's. How do I get them. What's the cheapest way --- or ... is there some other reason to go in one direction.

With NG available .... it almost always wins in the cost department.

I was looking at a 25 year payback .. and I was at 5 tones -- the house needed more and that was another well. The house got a VS Air source HP and propane furnace

 

[ddawg16]

Geothermal is a heat pump. It's just using the ground -- or water vs the outside air that a typical AC/ Heat pump that you see on the side of the house uses.

The most common type uses wells -- drilled to a depth and sized to the needed load or tons of heating cooling. The size and number dependent on building load. You can also use coils of pipe buried in the ground ... or even a pond. It's just heat transfer.

I'm a nerd with this kind of stuff and have looked into it every time I have built -- I can't make the numbers work ..even with the rebates and tax savings. The wells are too expensive and the load too high ... IE ..too many wells.

The advancements with common air heat pumps have closed the gap and made the numbers even harder to hit going geo.

Geo is taking a more steady ground temp .... vs what an air source heat pump will contend with in the winter If the ground is 55 in the summer -- it's pulling in 55 degree water vs what an air unit has to deal with ... maybe 90degree air.

What people need to understand .... 90 degree air can still take heat and air at zero still has heat. It's all pressure and refrigerant

Very good explanation....

Lots of cheaper ways to save money.

No ****.

I'm a big fan of 'doing more with less'.

In live in Southern California...we do NOT have AC. When I did my 2-story addition to the house, I took into account air flow. Hence, if we leave the master bedroom door open, all the warm air in the house flows up our stairs and out our open skylight in the master bathroom.
There are maybe 2 weeks out of the year where we 'kinda' wish we had AC.

When I did the addition...I replaced every window in the house with high quality double paned, low E fiberglass/vinyl windows. I also added lots of insulation. I even insulated the floor joists under the raised portion of the house. Hence, doubling the size of my house had maybe a 10% effect on my utility bills.

It's kinda like MPG on a car. It doesn't do any good to make your engine more efficient if you're leaking gas.

 

[karoc]

Salesman are just that salesman, they don't service them and I be willing to bet he doesn't have that system his self. Up front money is huge, like others said the payback is a long wait. That's if you never have any problems, should you ever need a repairman you might be put on waiting list. Where I'm at years ago the gas company was trying to get into cooling side of the business which only lasted few yrs then it went away. Expensive to repair cause only one place to get parts, and the skills needed to service them just not to many out there.

 

[jkeyser14]

So with a COP of 5.1, and a $10k per unit higher install cost, you're looking at a payback of ~15-20 years compared to a modern split-system air-source heat pump (even factoring in the state grant). Compare it to a modern mini-split with Hyperheat (or equivalent), and you're looking at a payback of ~30-40 years....

Don't get me wrong, I'm not saying anything bad about your system, just that a payback of 7 years compared to a standard air-source heat-pump is REALLY stretching it. Basically those numbers would have to be done with like the worst air-source heat pump possible, in the absolute worst-case arctic winter, with your geothermal system locked at the lowest-stage at all times (since the efficiency drops way off at full load).

You are ignoring the 30% tax credit which applied to the entire HVAC cost - ductwork, electrical for the furnace, plumbing of the desuperheater, etc.

Also, the $6k was for all the wells combined. Both zones share the same well loops. Total price difference for two zones was around $15k vs. a standard heatpump ($16k if you include the desuperheater for hot water). I had the $3k state grant and $10k in federal tax credits. Net cost to me was $2k-$3k over a standard two zone heat pump installation after all incentives.

 

[mhm993]

I went through the entire geo investigation a couple years ago. I live in the NE and keep the oil heated house moderately cool in the winter (65-67) and use the central ac about 7 days each summer. The power co had a significant rebate and discount program available.

And the numbers didn't work. The contractor estimated, as others said in this thread, in our climate winter savings are moderate, but summer ac is virtually free. Trouble is, I barely use the ac so dont get enough savings.
Curiously, the power company was running a related investigation to see if customers changed their heat and ac use after the installation.
If we were building from scratch, given the rebates offered then, it probably still made sense.
Right now the power company has rebates on regular heat pump systems—ducted and ductless.

 

[yeldogt]

You are ignoring the 30% tax credit which applied to the entire HVAC cost - ductwork, electrical for the furnace, plumbing of the desuperheater, etc.

Also, the $6k was for all the wells combined. Both zones share the same well loops. Total price difference for two zones was around $15k vs. a standard heatpump ($16k if you include the desuperheater for hot water). I had the $3k state grant and $10k in federal tax credits. Net cost to me was $2k-$3k over a standard two zone heat pump installation after all incentives.

The cost and number of wells is the factor ..... The geo equipment is more expensive but not enough that it's ever a factor.

It's all about the well cost and winter water temps .. colder winter water = more well capacity. The wells around me are just too much $$ .... Even after the AMT was taken out of the tax credit I was 40k plus ... If my total Propane cost for all uses is 2k .. what can I save? Even eliminated it's 20 years at current rates?

 

[American Locomotive]

You are ignoring the 30% tax credit which applied to the entire HVAC cost - ductwork, electrical for the furnace, plumbing of the desuperheater, etc.

Also, the $6k was for all the wells combined. Both zones share the same well loops. Total price difference for two zones was around $15k vs. a standard heatpump ($16k if you include the desuperheater for hot water). I had the $3k state grant and $10k in federal tax credits. Net cost to me was $2k-$3k over a standard two zone heat pump installation after all incentives.

Even with that tax credit (which is set to expire soon), the absolute best case payback is around 7 years compared to a standard heatpump (your system only achieves it's rated COP and EER at about 1/4 its rated load, and it drops off rapidly as you approach full loadl. Realistically, maybe 15 years. Compared to a minisplit you're still looking at well over 20 years.

Worth it? Maybe, provided the equipment lasts that long. Tough pill to swallow for a lot of people.

 

[ezzzzzzz]

My old 1700 sqft farmhouse had geo installed by the prior owner. It's about 15 years old. I love it . We're getting ready to rebuild the kitchen and add a second floor bath and office. My intention is to use the existing loop field and condenser (2 years old) with a new geo unit. If the loop field wasn't already there I'd probably opt for a regular heat pump system to save money.

 

[yeldogt]

My old 1700 sqft farmhouse had geo installed by the prior owner. It's about 15 years old. I love it . We're getting ready to rebuild the kitchen and add a second floor bath and office. My intention is to use the existing loop field and condenser (2 years old) with a new geo unit. If the loop field wasn't already there I'd probably opt for a regular heat pump system to save money.

It's always great when someone else paid the freight. Great being the operating cost. Love is the electric use.


Where are you with a loop ... they are not practical in many locations.

 

[jkeyser14]

Even with that tax credit (which is set to expire soon), the absolute best case payback is around 7 years compared to a standard heatpump (your system only achieves it's rated COP and EER at about 1/4 its rated load, and it drops off rapidly as you approach full loadl. Realistically, maybe 15 years. Compared to a minisplit you're still looking at well over 20 years.

Worth it? Maybe, provided the equipment lasts that long. Tough pill to swallow for a lot of people.

Yes, payback is 7 years. But the loop is warrantied for 50. And when the furnace needs to be replaced in 20 years I will be way ahead. Plus, the geothermal heatpumos will continue to improve just like air source heat pumps and will improve a lot over the next 20 years.