The biggest bang for your buck and quickest payback are likely to be with air-source heat pump. I think you've said you live in a cold weather area. Heat pumps designed for such areas function well even at and below the freezing mark. Below whatever your cross-over temperature is, use the existing system you have. It's sure to reduce your electricity bill noticeably.

Exposed ductwork in a retrofit situation is not uncommon. Think of loft homes with exposed metal ductwork - it looks fine. The beauty is in the function, not the appearance.

What are the details of your home, square footage, location, design temperatures for indoor/outdoor summer/winter, design water temperature for your boiler for floors & emitters?

What about the rest of your HVAC system including age?

A heat pump air-to-water or liquid-to-water might be a smart move with rising energy costs. What a hydrohydronic HP would give you in addition to heating & DHW is any type of hydronic air-conditioning (heating as well) with easy zoning for heating & cooling.

The big advantage of geothermal would be no defrost cycles - ever ! That’s a big deal in cold climates especially since electricity rates will likely go through the roof as we continue to transition to everything electric. I’m not home to check but I suspect our backup only came on for the 1st time this winter when we had a wind chill factor of -42 degrees Celsius. That’s still below -40 degrees Fahrenheit! Before that (early Feb.) the backup had not come on once this winter.

Another advantage of geothermal and hydronics is that setbacks are not necessary unless you want them for nighttime sleeping comfort.

IMPO

SR

" A heat pump air-to-water or liquid-to-water might be a smart move with rising energy costs. "

fsq, I believe air to water heat pump equipment is rarely found in single family homes in the US and also is extremely expensive equipment, a few times more expensive to provide the same capacity as an air to air (conventional) heat pump. Ground source heat pumps are even more X more expensive compared to air source heat pumps, an expense that is unlikely to be recovered in the OP's time window. Especially since I believe he has solar panels. Do you have differing information and experience with the US HVAC market?

" If you setback the temperature to require less heating or cooling, there is reduction in required energy and cost. No? "

I believe that's correct, the reason being, there's less heat loss (gain) to the outside when the indoor temperature difference is less. However, in the case of heating as an example, the loss does need to be replaced when the setback period ends. Most heat pumps have substantially lower BTU production than gas powered systems and the recovery can take hours and hours. A simple example, a house large enough to have a 5 ton heat pump can get, at best, 60K BTUs per hour. A gas furnace or boiler for that same house would likely produce over 100K BTUs per hour.

If that house has a 60K BTU per hour heat loss, a heat pump could keep the temperature from falling further but would not be able to provide additional heat to raise the interior temperature after a setback. The "no need to use a setback" BS is typical of heat pump sales people - there's no need to use a setback unless you want your house to stay warm, because a heat pump without a supplemental heat source (like electrical resistance strips or a supplemental gas appliance) can't recover from a setback in an acceptable time frame.

Re: Stax

Geothermal likes long, even, stable run times. If you stop them there’s a certain delay till they stabilize & reach peak efficiency again. Kind of like a diesel truck that is just left to run rather than start & stop.

A lot of efficiency is lost with setbacks. That heat loss will have to be made up. Variable speed equipment will just drop to a lower run speed and just cruise along. Many geo people I know don’t touch their thermostats but our clients do probably because they can and feel there’s an advantage. The disadvantage is wear & tear. Once these things are running properly, they’ll run almost for ever as long as there’s no loss of refrigerant. Compressor windings are ‘shocked’ with a current jolt every time they’re started. That shortens their life cycle.

We’re on vacation now, almost 3-weeks. I did not turn the thermostat down even 1-degree from that of when we’re home. I’d bet that the savings in kW would be very small even if we had. Also I know that the solar gain of our home is phenomenal - especially on the coldest days because it’s so sunny. The geo HP will be ‘OFF’ for hours till the sun sets and our envelope is not tight at all!

YMMV

Re: Elmer

The HP market is rapidly changing due to the demands for efficiency & decarbonization. As you know Liquid-To-Water geothermal heat pumps have been around for a long time. What is moving the residential market at a faster clip now has been the advent of the Cold Climate Air-To-Water heat pump but it’s contributed another function not previously available - liquid air-conditioning!

Every year there are more and more manufacturers coming out with air-to-water heat pumps and others with low temperature fan coil units and panel radiators. Once you’ve lowered the temperature of the water required at design conditions and can still comfortably heat, the efficiency of even an air-to-water heat pump competes with geothermal and surpasses natural gas and an electric boilers.

Systems are being designed today with water temperatures of about 110F meaning that a HP that can supply 120F water is ‘in the game’. That might be at design temperatures - worst case conditions that is only a very small percentage of the winter, with ‘Outdoor Reset’ water temperatures required are even lower on days that are anything warmer. Some system designers are designing around 95F at ‘design temperatures’. Add to that variable speed heat pumps, let’s say our Air-To-Water HP variety. What does that mean? It means that the HP spools down and efficiency shoots up almost unbelievably as it now only has to deliver water at only maybe 95F. What else does it do for efficiency? As the Air-To-Water is variable speed, it can deliver water at lower temperatures ‘as needed’ meaning no necessary need for a buffer storage tank and plumbing that was needed with single speed HPs to prevent short cycling. What else does it mean? It means that a much smaller size HP can do the job well compared to systems requiring higher water temperatures.

Also water is much more efficient than air to move around and is much easier to zone.

You asked about the US market, as this is not yet that common residentially. I attend and participate in nearly all the ‘Electrify New York State’ and ‘Electrify Manhatten’ and I can tell you that it is happening on every level, state, federal, municipal, institutional, private development - even utility.

This (electric) train is out of the station. I see that the residential market will be driven by developers incorporating liquid HP hydronics into high rise & multi level condo projects with each unit having their own liquid HP and being individual metered & billed. They’re not doing it for altruistic reasons, they’re doing it on bottom line numbers and previous successes.

Utilities are also heavily in the game because there are new sub divisions going up where gas is no longer allowed. Gas utilities using their same technologies of HDPE piping, pumps, excavating equipment etc can build out networks similar to gas but delivering water instead. Utilities can own, circulate, meter, deliver energy through water and never have to source gas for these projects. Home owners whether condo or individual homes in new sub divisions never have to invest and pay up front for drilling, ground loops, design etc up front, making geo liquid hydronic much more affordable yet still super energy efficient.

Even if you haven’t seen it yet, you might one day see it as a letter from your trusty gas utility informing you that the gas network in you neighbourhood is being phased out and that delivery costs are about to become impossible as you and a few others will be the only ones left on the network. I’ve attended these seminars as well.

There’s no question they’re after your gas furnace, gas fireplaces and gas stoves as gas will be phased out. It’s not only because of decarbonization but that new, viable, profitable business models have been created, proven and are being embraced.

Even on vacation in Mexico, I have been amazed and had to point out to my wife, how in your face (mine anyway because I know what to look for) how suddenly hydronic fan coils for hydronic air-conditioning and presumably heating now seems to be - and she has been pointing out to me all the LEED Gold Standard projects she’s seeing - and this is MEXICO!

Don’t bury your head in the ground - unless it’s to install a ground loop!

IMPO

SR

" You asked about the US market, as this is not yet that common residentially."

I think a more accurate word is - rare. And in much of the US, I suspect completely unknown,

I first typed a longer reply but I deleted it, not wanted to further redirect mtvhike's thread. I'll end my comments with this.

A couple of additional points:

We really like our in-floor radiant heating system. It's quiet and comfortable, which is why I would prefer to put in a heat pump to heat water. Its only disadvantage is the cost of operation, and its dependance on the grid, which does go down sometimes.

Any kind of heat pump involves mechanical refrigeration equipment which is noisy, but the financial advantage might make the difference.

I'm not sure what is meant by "setback", unless it is reducing the temperature at night. We have no setbacks, because the response time is so long. When I was commuting weekly from Long Island, I would set the temperature back to 40° when I left, and then turn it back up to 70° when I started my 6-hour drive back (my primary thermostats are remotely controllable). Usually the indoor temperature would be about 55° or 60° when I arrived, which was fine since usually we would go to bet then. The system has 8 zones, each with its own thermostat, so I can turn the temperature down for the room I'm not using (the guest rooms, primarily).

We have no cooling, because it's rarely necessary, although last summer it did go above 85° during the day, but always cooled back enough for comfortable sleeping. Also, the finished basement (4 of the zones) is always cool. Our home theater is there.

My location is NE NY, and it does sometimes get quite cold, but not as cold as it used to. This year there was only one week of consistently sub-zero temperatures, and last year, no sub-zero days.

Something you can quickly check to assess your options is to look at the water temperature your current electric boiler is set at. Heat-emitting equipment, be it pipes in floors or any type of radiator, have heat emitting capabilities per hour that increase and decrease depending on water temperature. Cooler water, even if 10 degrees cooler, flowing through your existing system will provide less heat to the interior living area. Check to see what water temperatures can be produced using a heat pump, and what the cost of that equipment is. If the number is lower than the current setting you use, the only way to use heat pump equipment with your existing setup would be to add more or larger emitters - radiators or baseboard units, in each room. That would likely be an expensive and difficult proposition in addition to the cost of the equipment. Stated succinctly, it may be a cost prohibitive option.

Report back what you find out.

FWIW, there is this:

Q1. What residential clean energy expenditures are eligible for the Residential Clean Energy Property Credit, and how much is the credit? (added December 22, 2022)

A1. The following residential clean energy expenditures are eligible for a Residential Clean Energy Property Credit of 30% of the cost:

• solar electric property expenditures (solar panels);

• solar water heating property expenditures (solar water heaters);

• fuel cell property expenditures;

• small wind energy property expenditures (wind turbines);

• geothermal heat pump property expenditures; and

• battery storage technology expenditures.

Elmer: the water temperature right now is 150° and the outdoor temperature is 40°. Last week when the outdoor temperature was -10°, the water temperature was 158°. And only one zone out of 8 was on, the master bath (because we like to keep it warm!).

jrb451: I've already used the solar electric property expenditures, and am interested in the geothermal heat pump property expenditures. However, other heat pumps are not included, so maybe I shouldn't consider the air-to-water heat pump.

mtvhike, I think you may find that most heat pump equipment can't produce 150 degree water, ground source type included on that list. So back to my earlier comment, if you want the same indoor temperatures with cooler water, you'll need to install either more radiators or an air handler with a heat exchanger inside through which ducted air circulates. And if you're going to have ducted air, you probably will find much less expensive solutions by using heat pumps to heat air rather than water.

Talk to HVAC contractors in your area, they're the experts. Most of us trying to help are fellow homeowners.

Not true that geothermal heat pumps can’t produce 150˚F water. They can produce up to 160˚F - without any defrost cycles ever - and that’s a big deal!

Crunch your own numbers as COP is not as high as other Geo HPs because it’s asked to do a lot (160˚F). You should have the electrical capacity because of your electric boiler. This could also supply DHW and heat a pool as well.

Nordic High-Temperature 160°F (70°C) Hot Water Heat Pump

IMPO

SR

I'm beginning to think this is a lost cause. My thought was that if I could heat the water up to, say, 120° before it enters the electric boiler, then that boiler would have less work to do. But I suspect the recirculating water is already above 120. I have no convenient way to measure that temperature.