Geothermal heat pumps in northeast

[martinicus]

Has anybody embarked on installing a geothermal heat pump? We are in the early stages of planning a two-story addition to our 1920 colonial in NJ, and I want to rip out our ancient single-pipe steam heating system. We don’t have central air yet either so will need to add ducts for that. My fantasy is installing geothermal forced air for heating, cooling, and hot water, and possibly even installing hydronic radiant floors in the new rooms that are tied into then geothermal (this may blow the budget), or at least electric radiant in the bathrooms.

We ready have solar, and possibly could add more depending on the new roof space available, along with powerwalls of course, to enable us to go nearly off grid.

Natural gas is still very cheap and available here (suburban neighborhood), which is why presumably more people haven’t gone geo. Ultimately i don’t know if it would ever pay itself back, maybe over 10-15 years, less if gas prices increase, but if the difference between the alternative (central air & gas furnace) isn’t too bad I’d be happy to spend it to lower our home’s energy usage & carbon emissions and increase comfort.

So has anyone gotten quotes for geo? Ballpark price? Installed it or decided not to? If you have geo, how is the maintenance been? If you’re in a cold climate is it warm enough in the winter, for 5F temps?

 

[mongo]

Hi,

First step will be a good heat load calculation to figure out what size system you would need (coldest day) and how much it will be used (overall temperature).
In terms of ROI, natural gas is 103,700 BTU (varies by supplier) per CCF (so if gas is $1 per CCF, that is $1/100/103.7 = $0.96 per 100k BTU), heat pump is 3,412 BTU/kw*COP (so if COP is 3, and electricity is $0.11 per kWh it would be 0.11*100,000/(3412*3) = $1.07 per 100k BTU).
Would you be running horizontal loops, vertical, or have a large pond for the geo portion? That impacts the install cost along with system size.

 

[martinicus]

Hi,

First step will be a good heat load calculation to figure out what size system you would need (coldest day) and how much it will be used (overall temperature).
In terms of ROI, natural gas is 103,700 BTU (varies by supplier) per CCF (so if gas is $1 per CCF, that is $1/100/103.7 = $0.96 per 100k BTU), heat pump is 3,412 BTU/kw*COP (so if COP is 3, and electricity is $0.11 per kWh it would be 0.11*100,000/(3412*3) = $1.07 per 100k BTU).
Would you be running horizontal loops, vertical, or have a large pond for the geo portion? That impacts the install cost along with system size.

Thanks. We have a third of an acre lot, long and narrow, so I presume the easiest would be a vertical loop, but maybe if they dug up our backyard it would just be big enough. Haven’t had anyone come take a look yet.

The house is 1600 s.f., with an addition might be 2400. We need to add insulation and air sealing as well as part of the renovation. On a cold winter month we might use 200 therms of gas, with a bill of $300-$400.

 

[mongo]

Thanks. We have a third of an acre lot, long and narrow, so I presume the easiest would be a vertical loop, but maybe if they dug up our backyard it would just be big enough. Haven’t had anyone come take a look yet.

The house is 1600 s.f., with an addition might be 2400. We need to add insulation and air sealing as well as part of the renovation. On a cold winter month we might use 200 therms of gas, with a bill of $300-$400.

Sounds like you would need vertical loops.
200 therm is 20MBtu, averaged over a month is 666kBTU/ day or 28 kBTU average. If you airseal well (add HRV/ERV) and insulate, your heat load should fit a geo system. However this may also reduce your consumption. It will likely be a geo for the reasons of geo since geo and gas are cost similar usage wise. System cost is in the 10k+ range for geo.

Other item of note: in the event of a power outage, you will need backup capability that can run the geo system vs the sub 15A circuit needed for a natural gas system.

Have you thought about roof mounted solar collector panels?

 

[SageBrush]

I've only read about geo-thermal. It is fairly easy to come up with energy and cost estimates that do not match reality and to end up disappointed. One pitfall is to not account for the energy consumed to push the water through the system.

In your shoes, I would be more inclined to retro-fit the old home to near passivhaus standard, and to build to at least that level. Then you can decide on a heating/cooling system that matches your new envelope. It is best to come up with an integrated design.

 

[martinicus]

Other item of note: in the event of a power outage, you will need backup capability that can run the geo system vs the sub 15A circuit needed for a natural gas system.

Have you thought about roof mounted solar collector panels?

We have 6KW PV now and hopefully could add more on new roof. Along with 2 or 3 powerwalls it should be good for backup, although will need to calculate the load per day of the geo. I haven’t thought much about solar hot water.

 

[Sparrow]

I am only a user and really do not know a whole lot about what I am using, but my Geo thermal system was installed about 10 years ago. I am also in the Atlanta area so not a NE USA owner. My system or systems (3 of them) are closed loop systems utilizing several 200 foot vertical loops and Water Furnace equipment. My house is and was all electric so there is no history of gas to make a comparison with.

I have not tracked power useage so I can not give you any percentages, but my feeling is that it saves quite a bit more in the Summer months with cooling than it does with Winter and heating. I had the system setup to feed hot water to my water tank, but after 6 or 7 years, the line to the water tank got full of crude and became useless. The energy savings for hot water in either event were small and I just had that element disconnected rather than fixed.

The equipment has been relatively reliable, but all 3 had their coils replaced under warranty a few years back. The bigger loop has also had a small water leak that has required water to be added every 6 months or so. From what I could tell when the service men were here, the amount of water leaked was only at most a couple of gallons, but even that little amount seemed to be able to cause the system to shut down. An automatic water filling system is I believe possible. We just never got around to it since it is pretty easy for them to check and fill it up at every 6 month service visit.

One of the systems, now has a coolant leak (not the geo portion, but the Freon or whatever it is called nowadays) and one of the options they presented was to replace the mechanical system. The geo loop would remain as is. Cost I was quoted for replacement was around $14,000. The current equipment is 10 years old and I decided it was a bit early to think of replacing it so I decided to have them work on fixing the leak.

 

[martinicus]

In your shoes, I would be more inclined to retro-fit the old home to near passivhaus standard, and to build to at least that level. Then you can decide on a heating/cooling system that matches your new envelope. It is best to come up with an integrated design.

Good advice, I have quotes for in-wall and attic insulation and sealing, but they seemed excessive so have been holding off, pending more planning on the addition & reno. Don’t want to insulate a wall that will get torn down. Wish we had done it when we moved in. I guess with these variables it will make it a bit harder to calculate the heating & cooling load. We’re just starting the process so once we have plans in place we’ll have more to work with. It will be exciting to have an efficient house even if we’re still burning gas.

 

[mongo]

We have 6KW PV now and hopefully could add more on new roof. Along with 2 or 3 powerwalls it should be good for backup, although will need to calculate the load per day of the geo. I haven’t thought much about solar hot water.

Co-worker has geo, along with the (30A?) breaker for the main unit, he has a 50A circuit for the auxiliary heat (also has a larger house/ unit). Data point of one: he recommends not getting it.
The 30kBTU number would take ~2 kWh an hour to run, so a single PW would drain in 6ish hours on a cold day.
Solar collectors can be used with storage tanks and a water to air heat exchanger for heat.
Also possible to set up system to use a natural gas water heater as the backup heat source. Or use a natural gas furnace as the air handler/ backup heat source.

 

[nwdiver]

A lot of this boils down to economics and cheap PV has shifted the equation A LOT in the last 5 years. Geothermal is unlikely to make economic sense unless temperatures <15F are a regular occurrence. There are several air source heat pumps that operate down to ~5F and they're typically 1/5 the cost of a comparable geothermal system. If you don't have central air you can get a ductless multi-split system that will zoned heating/cooling.

Solar thermal systems for hot water aren't economically viable unless you're in a tropical region and using a $20 black barrel on your roof. The best option for heating water is a ~$1200 heat pump water heater available at home depot. If you really want to go 'all-out' Sanden makes a CO2 heat pump water heater for ~$4k. But it's not really necessary unless you live somewhere it gets really cold. Depending on weather a solar water heater could actually use more energy than a heat pump water heater since the backup for solar water heaters is typically resistive heat.

It's generally going to be cheaper and more effective to use something slightly less efficient but A LOT cheaper and invest the savings in PV. For Example; You can spend ~$20k on a geothermal system that uses 5kWh/yr OR spend $7k on an air source heat pump that consumes 8kWh/yr and $7k on a PV system that produces ~8kWh/yr...

 

[Tamar]

I have a geothermal system and my best advice is choose the most knowledgable installer that you can find. The first system we installed had to be almost completely replaced after using a 50 year old established heating and cooling contractor who didn't know what they were doing when it came to geothermal. Using this website (since you're in NJ) would be a great place to start: Welcome to the NY-GEO website . One of their founding members flew out to Minnesota to help me remedy the mess our first installer left us with.

 

[EVSteve]

I highly recommend vertical loops. The system I have consists of 4 280’ deep vertical loops shared by two ClimateMaster 27 units. System has run very well though I question the competency of the company who did the ductwork. Mine was a retrofit to a 1940’s construction which had oil heat with no ductwork.

If the plan is to use the desulerheater for hot water and radiant I highly recommend going overkill on the loop fields. The incoming temperature of the loops has a drastic effect on the efficiency and temperature output of the heat pumps.

 

[mongo]

That's a good point on the air sourced heat pumps. Checking the data sheet on evacuated tube solar collectors, they are about 60% efficient at sun to heat conversion. So a 20% PV + HP with COP of >3 beats it.

I've been looking at the Chiltrix self contained air-water exchangers. That plus a natural gas furnace as air handler could give the best of both worlds. It can also provide domestic hot water off the same unit. If you use a natural gas tank for storage, you are good in any temperature without resorting to COP of 1 auxiliary heat. This would keep your backup power requirements low. The Chiltrix is solar friendly (variable speed low inrush compresssor) and will also do your air conditioning. So it could run off the PWs, or you could go gas for heat during the outage.

 

[SSedan]

Little more than a year ago we switched from all baseboard electric with crap high velocity AC system to Fujitsu minisplits in my 40yo house near Green Bay, I grew up just near Belvidere NJ so I know your climate and I think air source heat pumps like I have would do the trick for you.
IN sustained well below zero like 10-15 below I do run a small resistance heater in our livingroom, placement of the air handler was dictated by a LOT of glass and the far end of the room can get a little cold. If the air handler were located differently it would easily keep the room comfortable.
This resulted in the house being more comfortable year round and electric budget was coming down,6months in it dropped 20% with a colder winter, then I bought an electric car and haven't bothered to try and analyze the electric bill any more, too big a variable.
This was expensive but house is a bi=level with 5.5" above the basement drop ceiling and no room to drop it further so ductwork was out. Considered gas boiler and hot water baseboard but that wouldn't have fixed the very poorly installed 20yo HighVelocity AC system that was attic mounted and used 2" hoses to distribute air and a central return, bedrooms were in the 60s livingroom in the low 80s even leaving the fan run and diverting flow as best I could. Contractor who installed it was wildly incompetent, north bedrooms right under unit had 2 ports, same as the south sunroom/living room that is mostly glass with skylights and the ports were at the entrance to the room not the far end.

Even guests miss the fact there are wall units, yes it sounds bad to have a unit on the wall but you really forget they are there. I will say that cleaning the separate filters is a hassle compared to a central paper filter.

 

[martinicus]

Thanks all, lots of food for thought here. I hadn't thought much about air-source heat pumps, didn't know about their ability to handle low temps, and the the efficiency specs on the Chilimax look very good. I'm not sold on the ductless, as I don't know how I would manage all our small bedrooms when the doors are closed. But potentially hooked into a centralized ducted system could work. Wish we had more roof-space for solar expansion (since we got our Tesla, solar generates about 80% of our usage, not including heating). Unsure how much roof the addition will add. I'm guessing with the low price of gas, running costs of something like that Chilimax may be roughly equal annually, or slightly more than the equivalent gas costs.

 

[mongo]

Thanks all, lots of food for thought here. I hadn't thought much about air-source heat pumps, didn't know about their ability to handle low temps, and the the efficiency specs on the Chilimax look very good. I'm not sold on the ductless, as I don't know how I would manage all our small bedrooms when the doors are closed. But potentially hooked into a centralized ducted system could work. Wish we had more roof-space for solar expansion (since we got our Tesla, solar generates about 80% of our usage, not including heating). Unsure how much roof the addition will add. I'm guessing with the low price of gas, running costs of something like that Chilimax may be roughly equal annually, or slightly more than the equivalent gas costs.

Since you are talking about ripping out steam, the Chiltrix also has individual room units fed from the outdoor unit like a mini split. That would allow keeping unused rooms at a different temperature.

Using ductwork instead will depend on your house setup. You may be able to use a central return and only add supply ducts to each room (may need to add passive vents through partition wall or from door bottoms). Advantage of ducts is air quality control. Adding an HRV ensures an adequate number of air exchanges.

 

[SSedan]

Little more background.
I have a 2400sq ft. bi-level(basement sunk 4 feet both floors complete finished living space) went with two outdoor units and 3 indoor units handled by each. The there are three large spaces that have indoor units, then both upstairs bedrooms and a corner downstairs bedroom. The 4th bedroom is downstairs one window facing north so it has no AC need and still has baseboard heat as do the bathrooms and laundry room.
Most of the house is single pane windows with storm windows and when I changed the service door to the unfinished garage there was ZERO insulation around the door frame. House is fairly leaky, most of the windows inefficient and the air source heat pumps really impress me. It was very expensive, but warranty is 12years parts and labor and it will likely be longer than that before it pays for itself but the house is more comfortable which is worth a lot too.

If I had room for ducts I would have gone with a central system but given construction and layout that would have been ugly, would have required major downstairs surgery and while it would have saved money on the system the construction to go back and build a soffit around the ductwork that would have come down below 7feet, and might have had to give up a bedroom to locate the furnace.

 

[beeeerock]

We have a Waterfurnace system in our house. Two vertical loops with a backup electric element. It's been in operation for going on 18 years now, with good results. If I was building a house, I'd certainly be planning to install a similar system. I like that the temperature remains consistent day and night, season to season. We generally see a few weeks of below zero F every winter and summers are regularly into the 90's (F). The system keeps us warm all winter and cool all summer. I don't believe we've ever had the electric backup element kick in.

Honestly, I'd pay a premium for this system over natural gas, because it's so comfortable and.... not fossil fuel powered!

 

[EVSteve]

By the way in case this was not mentioned the federal tax credit for geothermal was reinstated recently. 30% of installed costs.

https://www.achrnews.com/articles/136527-geothermal-heat-pump-tax-credits-reinstated?v=preview

 

[martinicus]

You can spend ~$20k on a geothermal system that uses 5kWh/yr OR spend $7k on an air source heat pump that consumes 8kWh/yr and $7k on a PV system that produces ~8kWh/yr...

Did you mean MWh?