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> “additional efforts are needed to address common technical and market barriers to wider adoption by consumers – which include performance at temperatures of 5F and below, installation challenges, and electricity grid impacts during peak demand periods.”

There are definite market barriers at play. In my house in New England, I tried to replace my aged boiler with an air-to-water heat pump (after carefully verifying, via experiments during a cold week in February, that my heat distribution would indeed work fine at a supply of 130°F). Only one company was even willing to come out and provide a quote and their quote was around 2.5x the costs of "put another boiler in", such that the payback period would be "literally never".

If, after doing the research to find out about them and specifically seeking one out, I couldn't manage to make an air-to-water heat pump make sense, I doubt that very many of them are being sold. I suspect it's one of those items that, if more were sold, more firms would sell/install them, bringing the costs into the realm of economically reasonable (and lowering the risk of having a difficult-to-support heating plant in the decades to come).

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Was it a company that also did gas boilers?

If it's not a company that solely does heat pumps, I have heard a lot of contractors will give outrageous estimates because gas is simpler for them and they don't want to do it without the huge markup.

I had ground source heat pump installed with vertical wells in a city by a dedicated geo installer. The cost with tax credits came out not much more than a high end gas furnace and water heater. Going airsource would have been even more cost competitive, especially with the federal tax credits in place starting in 2023.

They did. To (only partially) guard against that, I made it clear that I wouldn’t be hiring them to hang a gas boiler. (That still allows them to prefer someone else’s gas boiler job over my air-source job, but at least prevents me bidding against myself.)

And there definitely would be more labor, more piping, and more electrical work to switch to an ASHP; that’s part of the market forces problem that is hard to overcome with anything other than large price increases for gas or larger direct subsidies for switching.

I watch the PBS show This Old House which takes place in the Boston area. The plumber / HVAC guy Richard Trethewey is a fan both ground ("geothermal") and air source heat pumps including the air source heat pumps that work at 0F and heat water for radiant floor heating. I'm surprised that more companies aren't doing it there.

The majority of their projects are pretty high end (and they tend to want to demonstrate new technology, because it's more interesting).

For the 'project homes', perhaps, but if you're going to go through the effort of building new or re-doing an entire structure, you might as well use the latest and greatest stuff/practices/code.

They also have many segments of smaller DIY jobs for simpler fixes/maintenance, e.g.:

* https://www.thisoldhouse.com/plumbing

They most likely get funding (in the form of steep discounts or free equipment) from the equipment manufacturers to do those installs. They’re called demo homes in the trades.

It’s a good way to buy a bunch of headaches if you do it on your own without manufacturer support.

The 'cast' of 'This Old House' is mostly MIT MechE grads who figured out they could make more money doing renovations for Route 128 techies than burning themselves out working at their companies.

Oh yeah, Richard Trethewey and Tom Silva are definitely MIT guys:

* https://www.thisoldhouse.com/21071273/richard-trethewey

* https://www.thisoldhouse.com/21071309/tom-silva

* https://www.thisoldhouse.com/cast

Well, they've done episodes like this: https://www.thisoldhouse.com/season-20-ask-toh/23197052/s20-...

Advanced technology being developed at advanced research labs: who would have thought?

But that doesn't change the fact that hosts are mostly 'regular folks' in the trades that hook up a bunch of wiring and pipes (or glue/nail/screw together a bunch of wood).

I had 'cast' in quotes for a reason- I was half thinking of Norm (though I don't think he went to MIT) and more of the various sub contractors that filter through the show (some of which seemed to be thinly disguised product reps). Still, you can't deny they were higher quality outfits than anything most of us are likely to run into.

I'm not seeing anything about mit... were you guys being sarcastic?

I haven't watched since a kid w/ the Bob Villa days....

I mean that did describe Car Talk

No they are mostly second and third generation trades people.

> their quote was around 2.5x the costs of "put another boiler in", such that the payback period would be "literally never".

Doesn't that depend on the costs of both energy sources?

Last year I made a similar choice, albeit at smaller scale, just for one water heater. Picked an electric heater with heat pump, also cost 2.5x more than plain electric, but 1/3 the energy cost. It will take a few years to pay back ...

> Doesn't that depend on the costs of both energy sources?

Yes, it depends on the costs and efficiencies of the competing energy sources, the difference in capex, the annual building heat load, the projected lifespan of each source, annual maintenance costs, and the interest rate.

I recently spoke to a well driller that also does geothermal well drilling. He was telling me that the systems are more or less obsolete at this point, as the air-to-air units have such a high SEER rating that the ground loops really will never pay off.

Is geothermal any quieter? I was assuming the ground loop pump would be quieter than the air-to-air fan.

There's no outside noise in a ground-source system (for all practical values of noise: it's just flow in insulated pipes). The pumps are nearly inaudible inside the mechanical room as well.

Inverter-based air-source outdoor units are nearly inaudible during any time when your neighbors are likely to have their windows open. When the weather is uncomfortable enough to have the units need to run at high-speeds, they are no longer inaudible, but the neighbors are likely to have their windows closed.

I'm looking at a system now that is 45 decibels - 10db quieter than my robovacuum which is one of the quietest in the market.

What attracted me to geothermal was the year round availability of 50F water - easier to extract winter heat at that temperature, and you could create a simple fan / radiator ducted air cooling system for the summer. The latter would actually store summer heat in the ground, and could be powered purely by solar.

I have been doing a bunch of research into geothermal recently and this doesn't seem to match with what I have seen. But it probably also varies a lot by location and such.

They appear to still be about twice as efficient as an air to air one, and have less parts and maintenance (no outside unit to deal with). Yes the initial install is a lot higher because of the drilling but that should last for decades. In the US there is also 30% rebate at tax time which helps cut the costs down a bunch too.

You're looking to spend at least $30k if you need a vertical system, probably a lot more. And from what I understand, they ground loops inevitably don't reach their expected lifespan, so you'll be drilling new holes sooner than later.

If you live in a very cold climate, I suppose with tax credits it could make some sense. For most people, AC + Natural gas is the cheapest way to go.

My house uses a heat pump + oil-burning furnace. It gives a pretty good combination of efficiency, and ability to handle really cold weather.

I think this is most of the way to what the future looks like: a high efficiency heat pump with cogeneration, so you can still burn propane or natural gas for heat and limited power to drive the heating system in an emergency (and if you don't have gas service to the premises, you have either a propane tank [1] or an exterior outlet to hook up outside). You must have a solution for when utility power is down for substantial periods of time.

During the winter storm that just passed, a friend in the Midwest called that their house had no power and was rapidly cooling. The utility could provide no ETA to resolution. I walked them through (over the phone) safely enough backfeeding enough power from a gasoline generator (outside, with the extension cord run through a basement escape window) into their furnace circuit to bootstrap the furnace (and run the blower fan) to keep the house warm so that the pipes didn't freeze and burst. If the HVAC system had had a small battery and some way to generate power from the heat it was burning, the gasoline generator would've been unnecessary. Perhaps an integrated thermoelectric generator [2]? A standby generator isn't financially practical for most folks ($6k + install).

(EDIT: to the safety folks out there possibly concerned, the furnace breaker and main breaker were tripped, and the meter was pulled to prevent any chance of harm to electrical linemen from inadvertently energizing the utility line; take no chances with safety, do not attempt this at home)

[1] https://www.amerigas.com/about-propane/propane-tank-sizes

[2] https://patents.google.com/patent/US5427086A/en

For others interested in preparing for a situation like this, here's a video laying out in reasonable detail what to do.*

https://www.youtube.com/watch?v=1JNuovFpCpQ

* I don't like that they skipped putting a bushing or an NM clamp on the back of the box into the furnace, but otherwise the video looked sound when I watched it a couple weeks ago.

I've been waiting to do this in the event of a power outage; that said, I'm really curious what the current draw of my furnace blower will wind up being. There is a label that suggests it has a peak draw of 8.5A, but that seems like a lot. Still, it seems like a nice backup plan in the event of an outage, even if I only have a couple kWh worth of battery storage.

Many furnaces use third-party controller boards with well-known suppliers. You might find in the furnace manual that there are different wire-to-board permutations to allow different fan (interior recirculating blower) speeds. From home testing a few years ago, I recall RMS currents 50%-80% of peak rated draw, but could be mistaken.

What's the model number of your furnace / blower? I've been doing a ton of research in this area as I'm remodeling my place and have several furnaces and duct loops to deal with.

From what I've seen so far, unless your unit is super old, the 8.5A is almost certainly just a 'peak' startup current that's overstated as well. Your blower should say something like "1/3 HP" and from there it's straightforward conversion of 1HP = ~750W so a 1/3HP would be 250W. On a 120v service, that's 2 Amp. With maybe 15% efficiency loss, at peak speed, the blower motor wouldn't be drawing more than 2.5A. It could/will draw more than that to start, but literally just for a second or two.

Thanks, that's useful! That was my thought w.r.t. startup current, since I assume it is an inductive load. The model is a Carrier 58STA090-14 and it is indeed 1/3 HP. Seems likely I could run that load off my car in a pinch, which is definitely a good option to have available.

So per the spec sheet -- the "Full Load Amps" for that model could actually be up to 5.2A per the bottom portion of the 90-14 column second from the right on page 5:

https://d1049ui2fjityy.cloudfront.net/userfiles/inriver/docu...

That motor has a switch so it could be in 3 different settings -- As shipped, the blower motor speed is set to be faster for AC (more draw in the summer) to prevent the coils from icing over, and then it's shipped to be the slowest fan speed while in heating mode, but it is possible that your installer changed that. If indeed it is in the "slow" speed for heat, then 2.5A would be about right.

Also anyone with a high efficiency furnace should be away there is a second smaller blower on the exhaust.

I don't know what's up with that, but the standard fix is to let the faucets trickle.

Challenging when you're on a well and your well pump requires power. Will your generator support 220V and the surge start a well pump requires? That surge is going to occur every X minutes to replenish the pressure tank as it depletes due to trickling. In this scenario, driving the 15A furnace circuit was a more simple fix.

Something else to consider: electric pipe heat cable to keep pipes from freezing draws ~7 watts per foot, is quick to install, and easy to power if you've planned ahead.

I guess I must plead ignorance once again. Maybe flushing the pipes would be possible? I just know I would electrocute myself screwing with anything more powerful than a laptop battery.

I happen to have valves that would allow me to drain almost all of my house to prevent freezing, but that's not universally the case (and even in my case, I couldn't drain the hot water tank fully without power without letting it just flood the basement).

Freezing pipes is one concern, though having heat for the humans is another pretty desirable thing, so if I could spend effort on something that would result in drained pipes and no heat or on something that would result in enough heat in the house to make that unnecessary, I'm going for option #2 every time.

> (and even in my case, I couldn't drain the hot water tank fully without power without letting it just flood the basement).

That doesn’t sound like it should be up to code? I’d expect building codes to require a floor drain where your water tank is.

Houses designed to be vacant in freezing temperatures will have a drain port at the main shutoff valve so the pipes can be fully emptied.

Unfortunately, this is not a universal feature in residential construction.

In an emergency you can often turn off the water main, and then disconnect the union that connects to the meter. Most of the water in the house will drain out.

Most houses, the curb is downhill but not all - and there is always some branch run somewhere with a loop in it under a floor or something. :s

Problem is high efficiency furnaces/boilers require a powered vent, so they need quite a bit of power to operate. And then you’d need to circulate “cold” air/water against the heat exchangers.

This usually adds up to several hundred watts.

New homes should be built to better insulation standards. You have to solve so much and use so much energy to solve for a drafty house or lack of insulation on the outside walls. Newer homes are factoring in the R-value of 2x6s and finding ways to insulate those now.

In this scenario, high efficiency heat pump with a backup gas fireplace. Those typically don't require any electricity to run as they can ignite off AA battery or a push button. My PC battery backups barely last 30 minutes on a wifi router because of conversion loss. Furnace fans also account for up to 1/3 of energy usage of a unit. Cogneration would add $5-10k to a home build versus a 50 gallon propane tank with a single emergency gas fireplace unit.

If you've got wood available, you could also have a wood furnace as backup, and / or an actual fireplace (an efficient one ideally, possibly a masonry heater if you have the space and foundations to handle that load).

This is a great solution too. I have a wood 'heatilator' (or fireplace insert) and during the recent cold snap in the Midwest I went through about 1/4 face cord of kiln-dried oak over 3 or 4 days (that's a lot by my standards). It kept the gas furnace mostly idling and the home warm (in the 80's by the fireplace actually, lol). Probably not exactly cost efficient with the cost of wood these days but I like being able to take some of the load off the gas furnace.

Most of the heat from a fireplace goes up the flue unfortunately. It’s one of the least efficient heating sources per the dept of energy (~15% efficient). A low tech solution is more thermal mass perhaps in high performance dwellings.

Wood burning furnaces are a challenge because homeowners insurance providers don’t want to insure dwellings that use them (but will if certain conditions are met, such as it not being the primary hearing source, professionally installed, etc).

Wood stoves are really efficient these days, hitting 70% plus, and it's Carbon Neutralish™ as a fuel source (obviously uses fossil fuels for harvest and transport and such, but that's only some percentage of the total)

I'm always amazed at the ability of our questionable 1990s wood stove to happily heat the entire house. It's a great backup heat source on days when it gets proper cold out, which is thankfully rare here.

> Most of the heat from a fireplace goes up the flue unfortunately.

Depends on the fireplace. Direct-vent gas fireplaces take outside air for combustion and then exhaust it, with no inside air being used in the process. There are also direct-vent wood stoves that can do the same.

Wood stoves can get about 85% combustion efficiency, but that's not heat-delivered efficiency (often 10-20% lower):

* https://www.epa.gov/burnwise/energy-efficiency-and-your-wood...

This is why very old homes have absolutely massive fireplaces in the center of the house - the huge size led to a massive thermal mass that would extract most of the heat from the circuitous smoke path inside.

The advantage of wood is you can burn it without any outside source of anything.

I was also without power last week for 6 hours.

I have a SEER 18 heat pump for cooling which can reverse for heating in the winter but it also has a natural gas burner. Based on the installer's advice we set the system to use the heat pump if the outside air is 40F or above and switch to natural gas below 40F.

The problem was that when the power was out the electronics in the system could not communicate with the thermostat in the house. My Nest thermostat literally said there was no system connected. I wish there was some kind of UPS to power those electronics and the blower fan.

Can't you just hook up a sizeable computer UPS for that purpose? That should run it for long enough to get you through most outages.

The heat pump will be a 240VAC load. Consumer-level computer UPSes in the US are 120VAC.

The 24VAC transformer for the control circuitry will be on one of the 120VAC legs, but it's likely the installer didn't specifically wire it to allow partial powering of just the transformer and electronics board.

Hm... you might be able to get away with ordering a EU UPS then, those are 240V, you'll have to add a center tap transformer and maybe mess around a bit with it to get it to output 60 Hz (that will only improve efficiency).

I think if you’re just looking to run the fossil fuel equipment from the UPS, you can do it by just ensuring that and all the transformers and controls are on that phase.

That will take an HVAC person who knows who things work rather than just following colors on a wiring diagram. Probably easier and more supportable than trying to import and mod an out of region unit.

Probably quite a bit more $ though. Anyway, I saw your message and figured it has to be solvable in a cheap and quick way, never mind me :)

There is, an inverter sized for the load with an auto transfer switch attached to a set of 100ah batteries will do what you're looking for. And that is what a UPS is on the inside. They just tend to use terribly small batteries.

Such setups are easy to build if you want it and running a 100-200w blower doesn't require too many batteries either. However, if you need to run a compressor, the number of batteries required to power that for 6hours would start to get cost prohibitive.

https://www.amazon.com/s?k=2000w+pure+sine+wave+inverter+aut...

https://www.amazon.com/s?k=220v+automatic+transfer+switch+50...

https://www.amazon.com/s?k=100ah+lifepo4+battery

This guy has accumulated essentially everything you could want to know about such setups, at any voltage, any reasonable power range, in various applications: backup systems, full off-grid, mobile power.

https://www.youtube.com/@WillProwse

https://www.mobile-solarpower.com/

For a 240v load, there are inverters that output 220v or you can use one inverter to power each hot line, just buy the batteries at the same time from the same manufacturer and ensure they will stay balanced. In your case you could also use a cheaper manual transfer switch if you don't mind going into the closet to flip it when the power goes out.

What model do you have? I currently have a boiler for hydronic baseboards and would like to move to a more all in-one-solution for heating/cooling that is predominantly electric. My goal is to move all my gas appliances to electric with solar but it would be great to have gas backup and gas for those cooler days.

> A standby generator isn't financially practical for most folks ($6k + install).

An Honda EU2200i generator costs US$ 1400 (and less expensive generators can probably be found):

* https://powerequipment.honda.com/generators/models/eu2200i

You also need an external plug, a cable going from that plug to a sub-panel, and a line going from the sub-panel to the main panel with an interlock device for safety, if you wish to avoid running extension cords.

There are dual-fuel generators that can also use either gas/petrol or propane, and some tri-fuel generators that could also be connect to a natgas pipes (and conversion kits that can be added to propane-capable generators).

The problem is that while all that electrical work is a weekend project for a DIYer, it's quite expensive to have a professional do it. So then you start bundling things (since I'm already paying thousands, maybe I'll just splurge for that Generac with the auto tranfer switch...)

(FWIW, I believe there is an aftermarket propane conversion kit for the EU2200i. Converting a gasoline engine to run on propane is straightforward)

The Honda EU2200i can be aftermarket modded to run tri-fuel. I did it to mine just in case, and currently have it set to run propane. A simple swap of a small part will let it burn natural gas instead.

I also like that I don't have gasoline to deal with - I can stock up a 20lb propane tanks and generally forget about it. Rotating gas is a giant pain if you keep enough on-hand for an outage of any appreciable amount of time.

Would you mind sharing a link to the part you mentioned?

https://www.amazon.com/Grenergy-Gasoline-Conversion-Generato...

https://www.hutchmountain.com/products/honda-eu2200i-propane...

If you are at all handy this is probably a 30 minute job, it involves cutting a single hole for the propane tank connection and otherwise can be done with a screwdriver.

It's been reliable for me going on 4 years now - although I only really have run the generator for maybe 100 total hours since then.

I haven't looked for some time, but there are also other kits on the market. I those these guys due to reputation on forums, and how clean it is to install.

Up in the northeast power goes out every winter. It also gets restored a lot faster than the midwest, personal experience, but the reliability of it going out at some point during the winter means that everyone has a wood stove and a backup generator. Portable ones are practical enough and wiring a couple of circuits and a plug for the generator is not cost prohibitive for most.

What I've found in traveling the whole country for a few years is that local power generation or storage always forces you to consider just how little power you actually need. You can pretty much never just power the whole house, or even a whole RV. Even 50amps is ALOT of power and trying to provide that from solar/generator/batteries is incredibly expensive.

So your real question is pretty much never going to be, "how do I power my whole house in an outage?" but rather, "What is absolutely essential to spend up to 3000w on?" and even then knowing that a generator putting out 3000w burns 20lbs of propane in about 4hrs and 3000w for 4hr on batteries would require 10 to 12 100ah lithium batteries at $350+ each.

I still agree with you that super efficient heat pumps are the future without fossil fuels but that probably also has to come with greatly improved insulation values in almost all homes regardless of region. Think double the current DOE recommendations. If you're running on electricity, you will feel the cost of every bit of heat you lose through the walls, roof, and windows. More insulation is a one time cost versus monthly, it always makes sense in the long run.

However, we'll need regulation to force home builders to invest in that instead of just adding unnecessary sqft that people never use but have to heat and cool anyway. For some reason people don't want to pay extra for a house that is well built and well insulated, they'd rather go with bigger is better even when it's already absurd, and builders have noticed this.

Mine is the same with a gas furnace/heat pump combo. It's great.

My house uses a NatGas boiler and in-floor radiant heat. It also has wood stoves for those -20F (or worse) nights when I need a little supplemental heat (or the power is out and the main heating system is offline).

A heat pump would be a waste up here in Alaska esp given I don't need A/C. Just opening the windows and running some fans in the summer tends to do the trick for cooling.

> Just opening the windows and running some fans in the summer tends to do the trick for cooling.

The problem with 'natural' ventilation is you also get things humidity, pollen, dust, etc coming in as well.

One of the major advantages of mechanical ventilation (like HRV/ERVs, which cycle the air) is that things are tempered and filtered beforehand. Sometimes you also want to deal with individual variables: the temperature is fine, but the humidity is off.

There's the expense of maintaining a central A/C, ductwork, etc., that I'd rather not deal with (not to mention electricity is expensive here). Yes, if the air outside is dirty (forest fires, volcanic eruption, etc.) you've got a point. HEPA filters can help some with this, I suppose.

Humidity isn't usually a big issue here most days. If anything, it can be a bit dry (but not as dry as running an A/C would make it). Though, I do have a portable dehumidifier I use when I need to :)

Is filtering incoming air (for a mix) necessarily the norm, though? Even in the rare high-performance homes built on spec[ulation], my sense is that filtering incoming air might be omitted, in favor of a single filter acting on recirculation.

And forced air can be quite dirty (dust/pollen/etc.) if you don't clean your ducts regularly.

It wasn’t the norm, but now that more people have pollen allergies and widespread summer fires are common again, it’s become more important.

My use case is similar. The oil furnace feeds hot water into a network of radiators. My design goal is to maximize the electricity outage that we can make it thru without frozen pipes, and it has to be on a budget (so no generator or giant UPS).

The house is mostly unoccupied (a second home). Operation in an outage has to be fully automatic - it needs an automatic transfer switch I guess. The typical indoor temperature is just 5.5C (42F) - this does not leave much margin for the house to cool down during an outage when outside is like -5C (or -10 or -20).

But it turn out that an oil pump and a water circulation pump do not draw THAT much power, so if I can run them off backup power (say, a new car battery plus an inverter), it should last for some time before ice has any chance to form.

I’ve got the same thing. I did a bunch of tests last year to figure out relative performance and costs of heating my house at various outside temperatures. This included doing fine grained electricity monitoring with an iotawatt and rough fuel oil usage using an ultrasonic sensor.

Of course, now I’ve got a ton of data that I haven’t finished building my automation with. And, unfortunately, I’ve got an annoyingly bad Lennox iComfort for my heat pump thermostat and may have troubles building the automation anyway.

Was it the company mentioned in the second half of this show:

https://youtu.be/TlX5z32T1J4

Air to water is pretty new technology for the U.S. As you mentioned most oil boiler hydronic systems are spec’d for a much higher temp (like 160 to 180F). I’ve been curious myself if you can salvage any of the existing baseboards with a 130F supply.

I have a 5 head mitsubishi cold weather mini split installed last year but I am still keeping my oil boiler for now for domestic hot water and supplemental heat. If I could switch that to an air to water heat pump for a reasonable cost that would be nice.

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