The hunt for the most efficient heat pump in the world

A new generation of engineers has realized they can push heat pumps to the limit.

See full article...

 

[dtremit]

I'm guessing the heat pumps they're discussing here are air-to-water heat pumps, which seem to be hard to come by in the US. Hopefully that'll change at some point; they'd be a much better option for even heating in colder climates.

 

[Chuckstar]

Curious if such efficiencies backfire when used as air conditioners in the summer, or if the efficiency works both ways. For instance, you’d definitely want to bypass the solar pre-heating when using it as an air conditioner.

 

[the cave troll]

Am I the only one who is pumped up by this news?

 

[Zakalwe_Cheradenine]

A2A systems can be more efficient. However here in the UK, air-to-water is more prevalent due to us historically using wet central heating systems. Plus there is a £7500 grant for replacing a gas boiler with a heat pump. It must be A2W though, which is a shame because I think that there's a real place for A2A

We have a General Election tomorrow and it looks like the anti-Green Tories will be wiped out (Yay!). Hopefully a Labour gov will be more supportive of the green transition.

 

[MMarsh]

I'm guessing the heat pumps they're discussing here are air-to-water heat pumps, which seem to be hard to come by in the US. Hopefully that'll change at some point; they'd be a much better option for even heating in colder climates.

A lot of British installations use an outdoor air coil and an indoor water (or water/glycol) filled buffer tank, then circulate warm water through the house's existing radiators. The most common complaint I see about these is that, because water is circulating at perhaps 35°C instead of the 50-70°C of a flame-fired system, you get a lot less heat per unit surface area of radiator in the house..... thus, you either end up with cold rooms, or else you need to replace the radiators with better ones. Other than that, they seem to work very well.

My own unit (in Ontario, Canada) is a WaterFurnace Synergy3D. It uses groundwater as the source, and has both an indoor air coil and an indoor water-filled buffer tank at about 35°C. Forced-air heating and cooling use the air coil. Hydronic infloor heating and the hot tub's heat exchanger use the buffer tank, and at some point I want to hook up a heat exchanger to preheat the feedwater going into the domestic hot water tank as well. The system is great. A vast improvement over the old oil-fired system.

We need a lot more contractors trained and able to install stuff like this in North America. And we need some more vendors of equipment, too, because nothing brings down prices like competition for volume sales.

 

[Zakalwe_Cheradenine]

The other big advantage of A2A is that you get heating and cooling. Very efficient both ways.
Unfortunately they generally do not do domestic hot water here, which is a terrible shame. In Europe there are loads of A2A heatpumps that do hot water.

 

[demonbug]

Curious if such efficiencies backfire when used as air conditioners in the summer, or if the efficiency works both ways. For instance, you’d definitely want to bypass the solar pre-heating when using it as an air conditioner.

I'm guessing they don't really work as air conditioners, since they are air-to-water systems; I can't imagine circulating cool water through a radiator system is going to be as effective at drawing heat out of a room as running warm water will be in heating it.

 

[Embattle]

Heat pumps are coming along nicely, so I enjoy watching and reading information about them and their advancements. I also enjoyed the video below that explains the aspect of why efficiency matters in multiple areas:


View: https://www.youtube.com/watch?v=EVJkq4iu7bk

 

[MMarsh]

Curious if such efficiencies backfire when used as air conditioners in the summer, or if the efficiency works both ways. For instance, you’d definitely want to bypass the solar pre-heating when using it as an air conditioner.

The efficiency works both ways. Heat pumps with an indoor air coil, whether water- or air-sourced on the outside, are amazingly good air conditioners, to the point where they need to turn down their VFDs or cycle off entirely even on very hot days.

Heat pumps that are water-only on the indoor side are generally not used for indoor cooling in residential applications. However, there are many commercial installations where such a heat pump is used to run a chilled glycol loop that runs through fan coils to provide A/C indoors.

 

[Zoc]

I'm guessing the heat pumps they're discussing here are air-to-water heat pumps, which seem to be hard to come by in the US. Hopefully that'll change at some point; they'd be a much better option for even heating in colder climates.

Perhaps those don’t work as well for cooling air, which is a key factor in the US.

 

[Zakalwe_Cheradenine]

A lot of British installations use an outdoor air coil and an indoor water (or water/glycol) filled buffer tank, then circulate warm water through the house's existing radiators. The most common complaint I see about these is that, because water is circulating at perhaps 35°C instead of the 50-70°C of a flame-fired system, you get a lot less heat per unit surface area of radiator in the house..... thus, you either end up with cold rooms, or else you need to replace the radiators with better ones. Other than that, they seem to work very well.

My own unit (in Ontario, Canada) is a WaterFurnace Synergy3D. It uses groundwater as the source, and has both an indoor air coil and an indoor water-filled buffer tank. Forced-air heating and cooling use the air coil. Hydronic infloor heating and the hot tub's heat exchanger use the buffer tank, and at some point I want to hook up a heat exchanger to preheat the feedwater going into the domestic hot water tank as well. The system is great. A vast improvement over the old oil-fired system.

We need a lot more contractors trained and able to install stuff like this in North America. And we need some more vendors of equipment, too, because nothing brings down prices like competition for volume sales.

Glycol systems aren't used that much here due to much lower efficiency.Monobloc systems with the compressor and heat exchanger outside in a single unit are the norm.
The highest efficiencies come from running a low flow temp....35°C or lower. Such systems need careful designing, especially when retrofitting into a high temp has boiler environment.

 

[Dark Jaguar]

Curious if such efficiencies backfire when used as air conditioners in the summer, or if the efficiency works both ways. For instance, you’d definitely want to bypass the solar pre-heating when using it as an air conditioner.

It's been explained to me that a heat pump is basically just an air conditioner with a "reverse valve", so it shouldn't affect the cooling mode's efficiency whatsoever.

To that end, the critical thing here is to make houses well insulated. Without proper windows and walls, even the most efficient heating and cooling solutions are very expensive to operate. New housing does have stricter regulations for that in many places, but... the old housing is still there and not going away any time soon. It'd be nice to make upgrading those buildings with better windows and stuffing better insulation into the walls (like stone fiber) as cheap and subsidized as it possibly can be. At the very least, let's get our angled roofing insulated.

 

[Zakalwe_Cheradenine]

It's been explained to me that a heat pump is basically just an air conditioner with a "reverse valve", so it shouldn't affect the cooling mode's efficiency whatsoever.

To that end, the critical thing here is to make houses well insulated. Without proper windows and walls, even the most efficient heating and cooling solutions are very expensive to operate. New housing does have stricter regulations for that in many places, but... the old housing is still there and not going away any time soon. It'd be nice to make upgrading those buildings with better windows and stuffing better insulation into the walls (like stone fiber) as cheap and subsidized as it possibly can be. At the very least, let's get our angled roofing insulated.

Only if it is air-to-air. In theory you could run cool water through a wet central heating system, but you are very likely to end up with condensation.

Insulation is a win-win. Even with traditional heating systems, a well insulated house will be cheaper to run.

 

[chemgrad]

The other big advantage of A2A is that you get heating and cooling. Very efficient both ways.
Unfortunately they do domestic hot water here, which is a terrible shame. In Europe there are loads of A2A heatpumps that do hot water.

AWHP systems have been able to do cooling for a while, you just need radiators with a condensate drain.

What ASHP systems also do DHW? The only systems I have seen that do HVAC + DHW are AWHP when paired with hydronic air handler or ducted fan coils.

 

[Chuckstar]

It's been explained to me that a heat pump is basically just an air conditioner with a "reverse valve", so it shouldn't affect the cooling mode's efficiency whatsoever.

To that end, the critical thing here is to make houses well insulated. Without proper windows and walls, even the most efficient heating and cooling solutions are very expensive to operate. New housing does have stricter regulations for that in many places, but... the old housing is still there and not going away any time soon. It'd be nice to make upgrading those buildings with better windows and stuffing better insulation into the walls (like stone fiber) as cheap and subsidized as it possibly can be. At the very least, let's get our angled roofing insulated.

I was thinking the efficiency difference would come from some of the ancillary things they are doing to maximize efficiency. As someone subsequently pointed out, running liquid through radiators might be an inefficient way to cool a home in summer.

 

[James McP]

The other big advantage of A2A is that you get heating and cooling. Very efficient both ways.
Unfortunately they gener6do not do domestic hot water here, which is a terrible shame. In Europe there are loads of A2A heatpumps that do hot water.

Most geothermal systems (ground-source heatpump) use a buffer tank that is also the hotwater heater for the home.

As a general bit of advice, anyone putting in geothermal should pay to put 2 or 3 extra sets of loops in during construction, especially if you are installing them in a basement. If you do only one loop and it fails, the cost for a replacement and re-routing is much higher once the structure is complete.

Thermal expansion, micro-quakes, neighbor with a jackhammer, etc. can all result in damage to the ground loop. My relatives put in geothermal in the 90s and put in spare loops. They lost the first one after about 19 years, the other two should last into the 2050s.

 

[rbtr4bp]

This reads quite sensationalistic and it's a bit disappointing to attribute this to "A new generation of engineers", as if the current generation has been asleep at the wheel. It's like describing hyper-milers inventing ways to increase fuel economy dramatically.

Certainly, custom systems can be more efficient than more generalized ones, but there are also factors that aren't engineering, per se - for example, the difference in inside and outside temperatures is important, so anyone could increase their CoP by simply lowering the thermostat. This can be done at the expense of comfort or, as with a floor or concrete wall, could be done with energy storage, allowing a smaller amount of heat to be delivered continuously with the thermal mass moderating the temperature excursions (very similar to a hybrid car with a battery.) So, yes, bigger heat exchangers or more thermal mass can help, but there are other considerations that make these not common is many areas - similar to the costs and complexity of passively heated homes.

I was in the biz longer ago than I care to remember, but I also recall how frustrating it was to get an accurate temperature measurement for characterizing performance. With these systems, you are typically looking at the difference in inlet/outlet temperatures, which might span 10 C, and being off by even 1 of a degree effected the results substantially. There are systems that do better about taking a temperature difference, but if you are taking separate measurements and subtracting, it's not going to work well. Add to that errors in flow rates and being able to characterize the measured temperature as being representative of the entire flow stream, and it gets really, really hard to measure these things. Use high flows to reduce the temperature rise, lower the thermostats, and move the sensors to show a slightly higher difference, and to the top of the chart you go!

Perhaps the most important part of the article: "albeit not peer-reviewed analysis, "

 

[LDA 6502]

We need a lot more contractors trained and able to install stuff like this in North America. And we need some more vendors of equipment, too, because nothing brings down prices like competition for volume sales.

Agreed. Here in the Sonoran Desert, most residential HVAC contractors are fine installing A2A ducted units or mini-split systems. Want anything else? Prices go up, available contractors go down.

I'm in an area where the daytime highs this week are going to bounce between 45C and 46C. I'm also on a time-of-use electric plan because I have two EVs I charge overnight. I'd love an A2W system with a thermal battery that I could chill overnight during super-off-peak hours (0.76¢/kWh) or morning during off-peak hours (2.37¢/kWh), minimizing the time the outdoor condenser runs during afternoon peak hours (19.31¢/kWh). Nobody I've talked to on the residential HVAC side has ever done anything remotely like that. The commercial guys don't want to bother with a contract this small. So my only good option seems to be whole house batteries that offset usage from my traditional A2A ducted heat pump.

 

[chemgrad]

I'm a huge proponent of AWHPs, if only because they get rid of the biggest problem (and expense) plaguing heat pump installation: the HVAC installers themselves.

Monobloc/hydrosplit systems don't run refrigerant indoors, instead running water lines. This makes it easier for DIYers than mini-splits, allows the use of PEX instead of copper (also a boon for DIYers), and allows lower GWP refrigerants (as many are flammable, you wouldn't want to run them through your house under pressure, although the US is slow to adapt lower GWP refrigerants because ASHRAE seems determined to placate the fluorocarbon manufacturers under the guise of safety). AWHPs can easily integrate with ductwork, and most units allow DHW in addition to heating and cooling.

 

[rbtr4bp]

Sorry for a second post, but also:
"There is a fundamental limit on heat pump COP known as the Carnot limit, says Kircher. In short, it means that the theoretical maximum COP will always be constrained in proportion to the difference between your outdoor source of heat and your indoor temperature. "

The Carnot cycle is a reversible one - it creates no entropy - and so is highly efficient. When you have a compressed liquid (compressed in the compressor, excess heat removed via a heat exchanger) entering the evaporator, that is a great example of an irreversible process (thermodynamically) and you just aren't going to approach Carnot efficiency. You can have a heat pump that just uses compression and expansion of a fluid remaining as a gas, and that can approximate Carnot, but you will never get the capacity you need for a home. High efficiency too often means low power and slow.

For those tripped up by reversibility - heat pumps act as AC units because the mechanically can reverse the direction of the flow, so expansion can happen inside when cooling and outside when heating. That is different from thermodynamic reversibility, where you could imagine running the process backwards and it still makes sense. It makes sense, for example, that you could compress a gas, let go, and it return (very nearly) to the original state. It is less realistic, for example, to put a drop of alcohol in a bottle, allow it to evaporate, and then expect somehow to reconstitute it.

 

[Chuckstar]

Agreed. Here in the Sonoran Desert, most residential HVAC contractors are fine installing A2A ducted units or mini-split systems. Want anything else? Prices go up, available contractors go down.

I'm in an area where the daytime highs this week are going to bounce between 45C and 46C. I'm also on a time-of-use electric plan because I have two EVs I charge overnight. I'd love an A2W system with a thermal battery that I could chill overnight during super-off-peak hours (0.76¢/kWh) or morning during off-peak hours (2.37¢/kWh), minimizing the time the outdoor condenser runs during afternoon peak hours (19.31¢/kWh). Nobody I've talked to on the residential HVAC side has ever done anything remotely like that. The commercial guys don't want to bother with a contract this small. So my only good option seems to be whole house batteries that offset usage from my traditional A2A ducted heat pump.

Is there an off the shelf solution for something like that? My experience has been that it’s easier to get a contractor to install something unusual if you find it off the shelf and they’re just the installer, compared to if they have to go figure it out themselves.

 

[Dark Jaguar]

Only if it is air-to-air. In theory you could run cool water through a wet central heating system, but you are very likely to end up with condensation.

Insulation is a win-win. Even with traditional heating systems, a well insulated house will be cheaper to run.

I'm picturing the bargain basement bare minimum upgrade, taking an existing AC system and adding the needed valve and circuitry to allow "reverse" operation, which I suppose would be air-to-air. I forget that not every region place has standard central air in the home and would need a full system installed to begin with.

 

[LieutenantLefse]

As it happens right now a work crew is here replacing my busted central AC with a heat pump. I'm in a cold region (Minnesota) so I'll still need a backup furnace - yeah, it's possible to go heat-pump only even around here but very difficult and expensive with an older home. So I'm not going to be on any leaderboards but it should cut my gas usage significantly, which I can feel good about.

One thing I was pleasantly surprised by is the contractors I reached out to were are all knowledgeable and on-board with the full range of heat pump systems, which is a marked change from a few years ago when "heat pump" == "mini split" and you want to replace your central AC with what?!? I'm sure the tax credits have a lot to do with that.

 

[rjsams]

One big advantage of A2A systems is you can incorporate an ERV or HRV and good air filtration. Technically the outside tech doesn't really matter in this case.

The HRV allows us to turn the air over without losing much heat or cool at any time during the year. It also goes though the filter on the way in which helps with allergies.

IMO the important thing with heat pumps is to get the sizing right and get a variable capacity unit. That allows them to be quiet and very efficient most of the year but in those few really cold or hot days they can still do the job. They cost a bit more but they save money long term. We went with a carrier greenspeed and based on energy use, it appears to be doing better than the mini split system on the lower floor.

If you have a home office I'd highly recommend adding zoning. In the past I had problem with the work computer warming the office room as much as 10 degrees (F) over the rest of the house. No longer a problem.

 

[TomWestrick]

This is an advertorial so that it as it is, but Midea apparently has a new air source heat pump efficient enough for Alaskan winters:
View: https://www.youtube.com/watch?v=2nOxwGOLpIs

 

[chaos215bar2]

It's been explained to me that a heat pump is basically just an air conditioner with a "reverse valve", so it shouldn't affect the cooling mode's efficiency whatsoever.

To a first-order approximation, sure. But as with any engineering problem, there are tradeoffs, and it’s reasonable to assume that a system designed primarily for heating might make some tradeoffs which could reduce cooling efficiency.

There’s no reason the efficiency of a well-designed heat pump system shouldn’t be very high for both cooling and heating, though.

 

[Zakalwe_Cheradenine]

AWHP systems have been able to do cooling for a while, you just need radiators with a condensate drain.

What AWHP systems also do DHW? The only systems I have seen that do HVAC + DHW are AWHP when paired with hydronic air handler or ducted fan coils.

Daikin have a split A2A system with DHW:

Multiplus

www.daikin.eu

In Europe a number of manufacturers also make DHW cylinders with an integrated heat pump, such as the Vaillant Aerostor. These could easily be paired with a multi-split A2A heat pump.

 

[fellow human]

As it happens right now a work crew is here replacing my busted central AC with a heat pump. I'm in a cold region (Minnesota) so I'll still need a backup furnace - yeah, it's possible to go heat-pump only even around here but very difficult and expensive with an older home. So I'm not going to be on any leaderboards but it should cut my gas usage significantly, which I can feel good about.

One thing I was pleasantly surprised by is the contractors I reached out to were are all knowledgeable and on-board with the full range of heat pump systems, which is a marked change from a few years ago when "heat pump" == "mini split" and you want to replace your central AC with what?!? I'm sure the tax credits have a lot to do with that.

Jealous. I'm getting my now-dead AC replaced with another due to the heat pump premium being too steep. A while ago there was a rebate program but of course my unit had to die after it ended.

HPs are at least double the price of AC which I suspect is because prices were raised for the rebate program and haven't come back down yet. Plus winter is very cold here and my understanding is the savings would take a long time - if ever - to recoup.

Oh well, at least I don't burn gasoline, that'll have to do for now.

 

[Patient Zero]

I'm delighted with my A2A heat pump that was installed in March. At that time the house (built in 1963 with poor insulation compared to modern houses) was sitting at 74 Fahrenheit with an outside temperature around 45. Yesterday outside was 102 with an inside temperature of 76.

The icing on the cake is that my solar/battery system covers the vast majority of the energy cost - a non-trivial item given the exorbitant price of electricity in California.

I don't know the efficiency of the system but I do know it's higher than the separate heating/cooling system we previously used.

EDIT: Spelling

 

[comrade1]

We have a ground-temperature heat pump in our 8-apartment new construction building in Zürich. After a several-week heatwave 4 or 5 years ago the building voted to put in the money to enable it for cooling too. It wasn’t much money - just have to reverse the system.

It works surprisingly well. I have yet to see the inside temperature get above 23C no matter the temperature outside. Interestingly, they can’t use the actual ground temperature in the inside loop because it’s too cool (11C I think) and will cause moisture condensation on the floors/ceilings.

 

[EtherGnat]

Slightly off topic... I live in the desert southwest and I'm interested in replacing my AC over the next few years with a heat pump, but every time I start searching I get overwhelmed with all the different kinds. Is there any site that will let me put in my parameters (mainly AC, but some heat too), climate, electricity costs etc. and make recommendations based on cost/benefit?

 

[LieutenantLefse]

While the efficiency was impressive, my thought during the reading of the article was, "I don't need heat."

I already have too fucking much of that. And the need for heat is already diminishing for most everyone these days. Outlier cases notwithstanding.

Heat pumps also come with a handicap for anyone who doesn't have a central heating/cooling system. Most older homes may have the heat system, but central AC isn't as common, and is much more difficult to put into an existing home. A fast Google Street View of ALL of the places I've lived in 60+ years of life (and weirdly, they all still stand today) shows one feature that they didn't have when I was a resident of that address: Air conditioners.

ALL of them in-window. And that ain't nearly as efficient as it should be.

So while heat pumps for heat are fine and dandy in those diminishing places where heat is needed, and knowing they can cool as well, you still have to have the means to put that heat/cooling to use. Newer homes will have it. Older ones, for the most part, won't.

Climate change sucks. More for some than others, at least right now.

Millions and millions of people in the northern US, Canada, northern Europe (just to name a few areas) will have significant heating needs for decades to come regardless of climate change. So those of us who want to do our part to slow down said climate change are very interested in heat pump technology.

To your other point, at least around here heat pumps are actually more popular/started sooner in homes without central ductwork, thanks to the success of ductless mini-splits. It's only recently that "central" heat pumps have started to catch up.

 

[scarletjinx]

A2A systems can be more efficient. However here in the UK, air-to-water is more prevalent due to us historically using wet central heating systems. Plus there is a £7500 grant for replacing a gas boiler with a heat pump. It must be A2W though, which is a shame because I think that there's a real place for A2A

We have a General Election tomorrow and it looks like the anti-Green Tories will be wiped out (Yay!). Hopefully a Labour gov will be more supportive of the green transition.

All my well wishes for a decent outcome for you guys across the pond.

Sadly, I think the UK is better positioned than the US when it comes to decent outcomes to elections.

 

[jlredford]

There's an interesting alternate scheme called Networked Geothermal, where the boreholes for the underground external heat reservoir are distributed around a neighborhood. Lots of houses and building can share the same loop. It's being tried right now in Massachusetts by the Eversource utility: Geothermal Pilot Project. They've built a mile-long loop five feet deep to service 36 buildings:


This has lots of advantages over boreholes for individual buildings: geothermal SCOPs are high, like 5, the holes can be drilled and maintained by experts, the system can be upgraded incrementally, and the total load is averaged over everyone instead of having to support a peak.

It has an interesting political advantage too - it can be maintained by a gas utility. That gives them an incentive to get in on this rather than resisting to the last shareholder. It incentivizes the unions too! You really want as many stakeholders on your side as you can get to make these changes happen.

More here: A Better Heat Pump Scheme.

 

[Haravikk]

A lot of British installations use an outdoor air coil and an indoor water (or water/glycol) filled buffer tank, then circulate warm water through the house's existing radiators. The most common complaint I see about these is that, because water is circulating at perhaps 35°C instead of the 50-70°C of a flame-fired system, you get a lot less heat per unit surface area of radiator in the house..... thus, you either end up with cold rooms, or else you need to replace the radiators with better ones. Other than that, they seem to work very well.

There have been a lot of advances in heat-pumps able to deliver hotter temperatures, which these COP 5+ units might be capable of? I'm hoping so, as we desperately need efficient units that can deliver higher temperatures for this to be truly viable in the UK.

That's because the other big issue in UK housing is how shit our insulation typically is, as well as a lot of housing stock having flat roofs that can only comfortably fit two or three inches of insulation (allowing for an air gap), which makes for pretty poor heat retention. Not to mention flat roofs being an absolutely insane idea in a country that's raining 90% of the time, yet we're still f'ing building them.

I know for my own home, my current gas boiler targets a 55ºC return temperature (heat of the water returning to the boiler through the radiator loop) so it heats at around 60-65ºC, and a lot of newer gas boilers in the UK do the same. But with the amount of insulation in my house that's only just enough to get it to a comfortable (19-20ºC or so) temperature throughout. And that's after I've added extra insulation everywhere that it's possible to (under the cladding, extra loft insulation, cavities etc. etc.). Only options we have left would be insulation under the ground floor, or deepening the wall and roof cavities somehow, but each of these is quoted well above my price range because the foundations and floors are difficult for various reasons (so ground floor insulation that might only be a couple of grand quickly becomes way more), and deepening the wall and roof cavities are both extremely difficult as well.

If a heat pump can deliver a similar temperature of water for heating though, that might be good enough? Tough to say – the UK has been building shit houses for 50+ years, and even new housing is pretty pathetic, as one the first thing the Tories did when they got into power in 2010 was rip up massive chunks of the building regulations. They gave the usual BS about rules stifling competition, even though if everyone is required to build to a higher standard of insulation then there's no way for it to harm competition, whereas (funnily enough) getting rid of the rule makes it really hard for manufacturers of well-insulated homes to compete since they can't compete on price against cheaply made prefab boxes with paper thin walls.

Going to be interesting to see if a Labour government will do a better job but I'm not holding my breath at the moment (despite very much wanting the Tories out) as they've gone out of their way to avoid pledging any really large sums in investment into anything, they're still showing what looks like an austerity platform. And that's how we end up with houses from the 2020's having exactly the same problems as ones from the 70's like mine.

/rant

 

[sporkinum]

I'm picturing the bargain basement bare minimum upgrade, taking an existing AC system and adding the needed valve and circuitry to allow "reverse" operation, which I suppose would be air-to-air. I forget that not every region place has standard central air in the home and would need a full system installed to begin with.

I have a 100 year old house. Natural gas boiler with hot water radiators on the ground floor with window AC. Upstairs is a furnace/central air that finally gave up the ghost last winter. For the upstairs, we run electric oil radiators for heat, and a windows AC to cool. Would a A2W heat pump be a worthwhile replacement for heat, or would it not be cost effective?

 

[FlyoverLand]

I spoke to a gent once while waiting to have my tires changed. He told me his well drilling company was boring holes in the ground and inserting a vertical array of pipes for heat pumps. Since the ground stays in the 50's F, and the air in winter can get down to -20F here, it would seem that using air on the condenser side isn't the best way.

Boring a hole is way better than trenching your entire yard in my opinion.

 

[mcswell]

Am I the only one who is pumped up by this news?

Harumph. Sounds like a bunch of hot air to me.