In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new units can heat the entire house for the same amount of electrical energy that was used to run the FAN in the old gas unit. They are crazy efficient.
Ducts are dead.
The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units including installation. Payback time is about 3 years. The system is oversized, but enables excellent zoning and of course provides cooling which is a must on 40C/104F days.
Why do they seem to be so much more expensive in the US?
I don't think the hardware is that expensive in the US, it's the installation (which costs more than the hardware).
And mistakes by installers will cost even more. Our installers didn't flare a line set connection properly and it leaked slowly and that was a very expensive bill (especially since refrigerants have changed so much).
Our Daikin indoor units have also had condensate leaking issues, probably due to poor installation.
Ductless heat pumps do seem like the future but I think there are issues with regards to condensate draining, air filtering, and indoor unit cleaning/maintenance and replacement that could be done much better.
I love our Daikin mini-splits (came with the house), but as you allude to I've had to become an mini expert on deep cleaning them. They've can get GROSS with mold when used for cooling, and the cursory filter only does so much. That being said, now they stay clean for a few years after a deep cleaning -- though my first few attempt before I refined the process did not stay clean nearly as long. (Proper water pressure and disinfect is key.)
Cleaning basically involves a dedicated cover + drain that diverts water to a bucket, and blasting it with what's effectively a "low power pressure washer" I can use indoors (carefully), and "Lemocide" to properly disinfect... And coil cleaner for the fins. Takes me a good 4+ hours per unit, largely spent preparing the area in case there is any rogue spray. (Though TBH I may be a bit obsessive about getting it right.)
I also had a drain leak as you mentioned -- blasting the drain line with aforementioned "low pressure washer" helped with that. Still a bit gross to deal with. (And learning how to properly disassemble and clean the drip tray is the final thing I've put off leaning for a completely-thorough deep clean... I'm a bit horrified anticipating what I'll find...)
I once looked at a house with a new GSHP horizontal loop installed in the desert southwest US. I talked to the installer and they said the loop was only 12” deep. There’s no way the ground maintains steady temp at that depth, meaning you’re losing efficiency in the hot months when you need it most. Not to mention thermal pollution which will exacerbate the problem and the risk of hitting the loop with even minor ground work. They were adamant it was a good design.
Unfortunately, many installers jump on the bandwagon without the necessary expertise.
I take your point, but installation faults in central gas heating are also very common, but perhaps less obvious. The main one I’m thinking about is poor sealing or placement of the return duct, causing entrainment of air from the wall cavity. Source: local experts, and then I inspected my friend’s houses (hah).
Ducts are still needed to circulate air, especially if you want to remove stale air (e.g., bathrooms, kitchen) and bring in (filtered) fresh air (to bedrooms).
A recirculating central heating system doesn't do that. As mentioned below you either need exhaust only ventilation, balanced ventilation or ideally ERV/HRV. All of the above are available in both ducted and ductless forms.
Not being snarky but why don't you just open the window for that?
I have a CO2 detector that I believe is a reasonable proxy for stale air. When it goes above 1000 I simply open the windows. By the time I remember to close the windows the reading is almost always below 500.
They're obviously no replacement for exhaust fans in bathrooms and kitchens, but there's a number of ductless energy recovery ventilators that can give you fresh air in your bedroom(s).
In have ducted mini split units in my home, made by Mitsubishi I designed the system to work with merv 13-16 filters. I can run the fans and filter my air as well as use the units for heat and cooling. I installed fresh air intakes on the return units that can pull external air when they are opened.
It's really a very good proposition. Has all of the advantages of central heating and the efficiencies the heat pumps
It doesn't get that cold in most places in Australia does it?
Heat pumps need to be scaled for the maximum heating or cooling load, whichever is greater. The optimal situation is that the heating and cooling loads are similar, but in colder parts of the U.S. the heating load is much larger than the cooling load and the case for the heat pump is not so good as a place where the need for heating and cooling are more balanced.
We have a brand new Daikin VRV system in new york and are currently working on retrofitting a nat gas heating solution - heat pumps aren't a good fit for anywhere north of Atlanta:
When it's really cold out (say 25F or below), the heat pump stops for around 10mins to defrost the exterior coils, which means no heat running at all in that period, and this pause happens more frequently the colder it's outside. The end result, our ~1400 sq place took more than 24hrs to heat up from 55F to 72F when we got back after christmas.
Also you don't save any money on operating it, even with the efficiency yade yada the cost of electricity will run you more than the equivalent in nat gas. So nothing but downside.
Great. You just eliminated approximately 15% of lazy screenwriter tropes for thrillers and action movies. Now they are forced to rely on replacing live surveillance camera feeds with a loop.
Are you asking why the Daikin Alira X is more expensive in the US? It's because it's not a brand that is normally found here.
If you went with a common US brand you can get a good system with 4 units and a 36,000 BTU heat pump unit for around $6,500 USD installed.
I don't love the wall units - they're pretty ugly, even the new ones. If you're getting a mini-split, the in-ceiling or wall cassettes that are hidden are really the way to go IMO.
In the Australian market, the efficiency of the in ceiling or in wall units is lower than the high wall units. They are also much cheaper to buy and install.
Same, and we have just implemented 2 x 7.1kw units along with about 7kwh solar panels. Our heating costs have plummeted and we can survive on days like today (17th Jan) with minimal impact to our comfort.
We are looking at changing water heating next as this is now the biggest part of our utility usage.
Regional Vic for me, Daikin Alira X's installed in rooms about a month or two ago, and they've been great. Very energy efficient, and individual units in each room means we can match everyone's preferred climate -- even heating one room while cooling another! Main downside is that you need space for more inverter units outside.
They're pretty quiet, too. You can certainly hear the air coming out, but it's fairly quiet and certainly wouldn't be noisy enough to bother you over tv, work, or anything else.
I got a similar setup for my house as well. Being able to selectively cool rooms that are in use is great. However, I do wish the insulation was far better. Unfortunately I’ve noticed that Melbourne houses are usually very poorly constructed due to expensive raw materials and labour.
Have you examined your insulation with a thermal camera? Might be worth your while to get an energy inspector out. Personally I haven’t yet, mostly because I can still see low hanging fruit to fix.
Ducted heatpumps are a thing here in NZ and make sense to me, not that I have used one. The heatpump sits in the roof and air is pushed into three or so rooms through ducts.
If building a new house I think ducts would be the way to go.
You have to think carefully about where you run the ducts. They can be a huge source of energy loss. 40% is the number quoted by the EPA.
Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency.
I thought this was absolutely the solution but backtracking a little now based on experience so far.
We have a two-level, five bedroom new build in Auckland which came with a single-zone ducted system. So outputs are the bedrooms plus upstairs and downstairs lounges. The vents are tidy and unobtrusive - much less space than a wall unit in each location.
We're having major issues balancing the temperature across the different rooms as there is one thermostat.
Think setting the temperature overnight for one room with a couple plus a cat vs another room with one of the kids. Basically the wife and I are always far too hot because otherwise we're freezing all the other rooms. Or setting a reasonable temperature in the lounge makes all the rooms icy in short time.
I'm now thinking about forking out the couple of thousand to get a small heat pump installed directly into our room so we can run it separately from the rest of the house.
So if building from scratch, either look into a multi-zone system or separate heatpumps. If you can get separate systems but hidden in the walls/roof that would be the best.
The problem I have with mini splits is that they are an architectural eyesore. Are there any high quality ones designed to be built into walls discretely like cove lighting has done for lighting?
Ducts are good for indoor air quality though. Keeping our central fan on at low speed all the time significantly reduces measured CO2 in occupied rooms, particularly bedrooms overnight.
I am leaning more to this solution for this reason. Trying to get any tradie quickly these days doesn't happen. Trying to get an aircon person in an Australian summer is worse.
I despair for the rental market right now. High prices and landlords are generally crap at amenities they don't personally use.
Indeed, sounds like a problem with the fan. My 3000sf house uses 1100W for the fan, and about 4000W for the heat pump. I expect converting to mini-splits would increase, not decrease my overall power usage.
Just to add to what the other commentator said, ducted based systems are VERY hard to balance. It is possible using something called an Volume Damper, but it is uncommon (and adjusting them can be challenging, sometimes requiring removal of drywall).
So people COMMONLY wind up with unbalanced floors, and people typically try to fix it by adjusting the vent register opening with mixed success.
Part of the problem is that the thermostat is biased to wherever it is located. You can get systems with remote add-on temperature sensors, but that doesn't by itself adjust where heat/cold is being sent through a ducted system.
The great thing about a Mini-Split is that you're, at minimum, heating each floor independently with its own thermostat. You can then put in e.g. interior door vents that simply let air pass between common areas and the rooms when the doors are closed.
This can go even further with for example two Air Handlers per floor (quad units) on the east and west. So that as the sun moves, the correct level of adjustment can be applied to only the side of the floor that needs it.
How would it behave in a place like Chicago where we've had recent weather events that take the temperature from 40F to -10F in a couple of days? Will the system catch up that fast without ducts?
How does it function on a day like today? My evaporative cooler works decently at this temperature but with the side effect of making the floorboards sticky
> owners of drafty homes may need to take on the added cost of insulation when installing a heat pump
Installing good insulation is also really important even if you're not using heat pumps! With bad insulation, you're wasting energy no matter what technology you're using.
I've heard folks who work in the home energy audit business say that upgrading insulation is usually the most cost-effective thing you can do to lower energy bills. Even better, it's multiplicative with other activities like installing heat pumps or solar, so you can install a much lower capacity system and still hit your energy targets.
Most definitely. Here in Scotland, 'Home Energy Scotland' offer grants and interest free loans for various energy efficiency and renewable measures, but for the former you must install roof or cavity wall insulation if its recommended on your energy performance certificate for the building - I'd assume purely because it's the most cost effective measures when applicable.
And in the United States at least, the IRA contains tax incentives for all of that. The audit, the added insulation, the heat pump, and even more efficient appliances.
It’s not always possible. For instance old wood double hung sash windows require a weight box to work. Those boxes can’t really be insulated. And there’s a good chance you don’t want to replace the old windows (or possibly can’t due to historic restrictions) because they are a massive part of the homes character.
Also insulating an old home (pre-WW2) could begin to introduce moisture issues in the walls that weren’t there the last 100+ years since the leakiness of the home would dry the structure. Last thing you want is for condensation and water vapor to build up in the insulation and then begin to rot the wood. Modern build have vapor barriers and airtight seals.
I guess my point is to be careful with old structures without considering things. They were built the way they were because those were the materials we had (old growth wood!) and they were designed to function a certain way.
> For instance old wood double hung sash windows require a weight box to work. Those boxes can’t really be insulated.
In Denmark, this was solved by adding a second, modern window on the inside. The outside kept the same look, and it is even more insulating than a single modern window. Is it a bit clunky to have to open two windows ? Sure. But it is better than not having insulated windows, or ruining the appearance of cities.
On the contrary modern houses often rot because of the water barrier. Condensation gets trapped in the wall and it rots really fast. If you insulate your old house from the inside you wont have this issue. I spent the last 3 years remodelling at 1875 house and we opened all the walls to spray urethane foam. It sealed all the cracks between the wood beams but still leaves the exterior untouched to moisture can leave.
Also, you can use heat pumps with poor insulation just like you can use traditional heating solutions with poor insulation. It's just that you will need a larger system that wastes more energy. Whether that's still worth the trouble in terms of cost of course depends on your current situation of course.
But it's not like heat pumps stop working because of your insulation. They just get more costly to operate. And especially the smaller systems can only deliver so much energy to your house. Basically, if you multiply the maximum output by three, that should be above whatever you are currently using to heat your house during a really cold month. If it's lower, it's not big enough.
If you live in a warm climate, I personally think insulation is the worst (excepting roofing). Not because of efficiency, but because you isolate yourself from nature! The traditional Queenslander (look up Bluey if you don’t know what I mean), has so much going for it. It allows airflow through the whole house, a protected outside to sit and be with nature, lizards coming and going, bliss!
This hermetically sealed environment that we create for ourselves is bad for us.
That can work just fine by intentionally opening windows. Having a "drafty" house is just forcing that 100% of the time (which isn't always wanted).
Side note: As a US resident in an area with a ton of mosquitos, I cannot understand why other countries don't heavily use window screens. Lizards a pretty cool, flies and other flying bugs are just annoying and gross.
Insulation can be orthogonal to fresh air. Ventilation energy recovery units [1] exist to help reduce loss from fresh air (and are code for new houses where I am). This has the benefit that you can have more fresh air, for the same heat loss, since the loss will be from the fresh air, rather than through high thermal conductivity through the non-breathable portions of the walls.
Australians have a very strange relationship to insulation and temperature.
Some might say it's the defining feature and purpose of having shelter is that we don't live at the mercy of the weather.
I can't run a business with indoor temps from 24-31c during business hours. Compounding loss of brain function outside of 18-23c is found by every study I've read.
The less exposure to particulate pollution and extreme temperature, the healthier you are, I can't see any arguments otherwise.
The Queenslander house style was built for large blocks that had sufficient airflow, they were built to be cheap and don't work properly with modern block sizes.
While they are iconic, and have some great design features, the lack of insulation is not one of them.
A modern well insulated house with a heatpump + solar is extremely energy efficient and comfortable in all weather.
Queenslanders work fine in Queensland, where the lows in winter are still double-digit C. Most of the world (or even Aus) isn't like that. A Queenslander in Canberra would have a massive heating bill 8 months of the year to keep it safely livable.
Yes, true. I kind of lump them together when I think about them, and I think they're often remedied together during retrofits, but they're different issues.
Why can’t my whole home participate in this technology? It would seem an ok fit for things like freezers, refrigerators, hot water heaters, etc.
When it’s freezing cold outside, it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated.
Someone needs to make a standard for moving heat/cool through all appliances in a house…
> it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated
The fridge is simply moving a little of the warmth in your room out of its box, and adding a little more warmth to the room in the process. You lose no heat from the room, which is what matters, really. It would be worse to dump the heat outside! At least in winter. The heat has to be removed in summer if you have air conditioning.
In any case, an exterior heat exchanger and heat pump that can handle a wide exterior temperature is much more heavy duty. This could all end up being less efficient, in practice. House-scale heat pumps can efficiently move heat even from a freezing cold outside into a warm interior. Just as fridges can efficiently move heat from their cold interiors to a warm room.
I always joke that in winter all appliances are 100% efficient (I know they're not). Some look at me funny but the ones who pay the gas bill get usually get it.
The smart thing to do in winter is put municipal liquid water in your freezer, and dump it outside once frozen to thaw in spring. Rince repeat all winter long.
Voila: everyone has heat pump heating! (And dead compressors).
The dumb thing is having the compressor itself indoors in summer. Should be outside.
The fridge isn't the biggest energy hog in the house, but I'm very sympathetic to the absurdity of heat levels in a house.
I often see my HVAC cooling when the set-point temperature is actually _higher_ than the outside temperature. Logically, the house is a heat generator, it makes sense physically. The roof is black, etc.
It would offer a good number of benefits if the system could outright open a duct to the outdoor air, and suck it in whenever the local outside temperature is within the range requested by the user. People who are into optimizing energy use (they exist) can go even further and pre-cool their house during the night in summer.
For this to work, all you need a pusher fan, no refrigeration at all. There might be some pressurization problems, like, you may need a duct both for the intake and outlet. Also might require another filter... but air quality would improve significantly.
This is a really "dumb" idea, but it's perfectly in-line with all the new ideas being thrown out there. The new ideas just tend to throw in an additional heat storage mechanism, like a water tank (in the article). You can get a lot more efficiency gains by saving the night's cold in a tank and using it through the day. But on a more basic level, you can pump straight into the house when the conditions are right.
I've built/retrofitted and a prototype of mechanically operated louvres with push/pull fans for air exchange in an old school building, tied to the thermostat, ac, and a CO2 detector.
The idea of doing the same in my home has been taunting me for years now. Ideally you'd have two such louvres, one with a push fan in the upper floor and the other with a pull fan in the lower floor to simultaneously eject unwanted heat, bring in fresh air, and boost whole-house circulation. They'd be set up to interface with the thermostat/hvac and would operate when the outdoor temperature at intake is lower than the temperature at exhaust and both are above the set point on the ac.
The biggest problem is really one of convenience. You'd need a filter on the intake and a rather large and powerful fan to overcome that static pressure - ergo, a noisy one. And you'd probably have to fully dismantle the system in the winter to prevent the cold from getting in (the Midwest is cursed with both hot and humid summers and cold and dry winters). It just end up being the kind of thing where the devil really is in the details and you either do it right and it's a huge undertaking or you do it fast and sloppy and its drawbacks won't be worth it.
But I agree, nothing is more infuriating than seeing the AC on and the outdoor air temperature being lower than that of the home. And opening windows just doesn't make a difference since in most 20th century homes there's just poor airflow and no circulation.
I've often wondered if opening windows while AC is running and outside temp is below inside temp is less efficient than keeping them closed.
My thought is I should keep them closed due to extra load on the AC to dehumidify the outside air. Or open windows and turn AC to fan-only mode to prevent stagnant air in rooms without windows.
You are exactly describing a HVAC "Economizer" as they are called. I believe they are almost solely used in commercial HVAC installs, probably due to price/additional install complexity? They are very neat though, and do save significant energy in shoulder seasons, or at night in the summer as you mention.
The function to just bring outside air when it makes sense is an extremely common feature in commercial HVAC systems - it’s called ‘night purge’.
Most of these systems have a damper that the system can use to choose how much fresh air is used or how much return air is recirculated so it’s not difficult to use that to just put fresh air in directly with no cooling or heating. Even systems with heat or energy recovery will often have a bypass damper.
You need the humidity to be in the right range as well as the temperature, but it can save a lot of energy!
You'd need one of three solutions to make this work:
1) Long refrigerant pipes. This is unacceptable because it increases the amount of refrigerant in the systems (refereed to as the charge of the refrigerant). Refrigerants are powerful greenhouse gases so it is important to design low charge systems.
2) Another process fluid (e.g. water or glycol). This adds expense (more pumps and heat exchangers). You'd increase the cost of all these systems by a lot.
Also, both 1 and 2 involve running a new set of single use pipes around your house.
3) Make a "single appliance" household. A design like this has been tried - single AC/heat pump hooked to fridge, freezer, oven, dishwasher, washer/dryer, and water heater. The problem is that you really have do design the house around this and it is quite limiting from an architectural perspective.
Combined AC/heat pump and water heater is a thing though.
Adding to (2), I've worked with liquid-liquid heat exchangers (large heat/chiller units for chemical reactors) and they are super quiet and efficient, but boy howdy, are they messy and high maintenance. The glycol lines leak, the water supply leaks, the water needs to be screened and the screen needs to be changed.
Air-sourced exchanger individual appliances are just so much simpler for the consumer.
Not dissing ground-source heat pumps. Those are fine, since they are typically a plumb-once-and-done. You just generally don't want separate appliances which quick-connect.
> Why can’t my whole home participate in this technology? It would seem an ok fit for things like freezers, refrigerators, hot water heaters, etc.
At large scale (think like walk-in coolers of supermarkets), this is actually being done in the form of district cooling [1].
> Someone needs to make a standard for moving heat/cool through all appliances in a house…
The problem is that the piping itself and the circulation required are sources of energy loss, and it's hard enough to keep these appliances sealed so they don't leak their coolant - most coolants have insane CO2 equivalent potentials. It's not worth the effort.
It is technically possible. I had the same thought as you and looked into it some time ago. The only references I ever found to it actually being implemented were in cases of giant walk-in (even warehouse sized) refrigerators/freezers in places where district cooling exists.
For something the size of a home fridge the costs would be immense compared to the energy savings. You're far far better off spending that money on more efficient heat pumps and more/better insulation.
The federal limit for the amount of power a fridge can pull is 527 kWh/year, which at my rates (admittedly on the low end these days) is ~$70/year. There are very commonly available fridges that are < 300 kWh/year, which would be ~< $40/year. So before even taking into account the efficiencies you implicitly make back when you're heating your house anyway, that's your per-attached-appliance limit for input cost on building out, maintaining and running that system.
Though, I admit that the idea of a completely silent fridge & A/C is alluring. Here's to hoping we make some breakthroughs on sold-state heat pumps.
The good news is that the process of running your fridge moves the heat from the fridge into your home, which in the winter is not such a big problem. Your fridge is just another heat pump. It's a bigger problem in the summer when you are maybe trying to cool your house using air-conditioning and your fridge adds heat to your house to keep the fridge cool. Much less desirable.
They move the heat from inside the fridge to outside. That heats up your home. This reduces your need to heat your home, temporarily.
Generally, every device in your home that uses electricity is creating roughly the same amount of heat as an electric heater would have using the same amount of electricity. Even fridges and freezers, so long as nothing is being vented outside.
Devices are beginning to appear that can move the waste heat generated by home AC compressor into the pump loop for a swimming pool outside that same home, getting your pool heated for free by cooling your house, and your aircon cooling becoming much more efficient by using your swimming pool as a giant heat sink.
However unless the house was built, and / or the pool installed in a coincidentally fortunate configuration where the AC compressor and the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
> nd the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
that makes no sense. effective insulation is no problem at all. In large parts of europe they even have centralized water heating and run insulated hotwater pipes to houses across kilometers without huge losses, hell, for this kind of setup it would even be possible to just run refridgerant, which typically specs at ~15m for minisplits as maximum(with very minor losses) distance
Note that this is only an advantage in cooler months, and does work against cooling your home in hotter weather. In principle it seems like we could could build our refrigerators into an outside wall (like iceboxes once were) and then expose the coils in summer, and enclose them in winter.
Not really, efficienty aside the heat it puts out the back is coming from inside the fridge... Which is coming from the room housing the fridge. So over the course of a day it should be neutral.
I think you are looking for (one specific implementation of) Cold district heating.
It can be implemented as a single line of force water flow with 20-25 Celsius. It is viable as both a heat source and a heat sink at the same time.
This thing can be connected to both your coolers and heaters, and thus transfere heat from one to another. Maybe you could even get you desktop computer into the loop.
Usually it implemented on a lager scale, but i don't see why this would work scaled down.
In order to cool your refrigerator, the system has to have a place to the put the "hot" it just extracted. And that place is your house itself; your freezers and refrigerators are warming your house and contribute just like the radiators you installed. So the losses are not as big as you expect them; the money you spend on those appliances also lowers your heating bill.
> the money you spend on those appliances also lowers your heating bill.
It should net out to no less than the same energy though, right? That refrigerator needs energy to move the heat out of the fridge and into the home. If that process takes more energy than just letting the house HVAC deal with it, wouldn’t the energy bill be higher?
Just to be pedantic, but not exactly. The typical design in a domestic heating unit, or refrigerator is mechanical. A fluid is pumped and cyclically compressed/expanded. While electric motors are usually used, they can be driven by any source of mechanical energy; driven directly by a combustion engine is not too unusual.
There are also heat pump cycles that can be driven directly with heat. Refrigerators based on that are relatively common here in Canada in areas without reliable grid electricity. Usually a propane or natural gas flame.
Thermoelectric coolers are actual electric heat pumps; directly moving heat across a semiconductor junction. Not very efficient and quite expensive practically. They're used in those USB drink coolers and to cool down lab equipment. Finding a high-efficiency thermoelectric material that works at normal temperatures and pressures is nearly as much of a Holy Grail as finding a high temperature superconductor.
Strictly speaking you don't need a phase change in the fluid for a viable heat pump; pressure change is enough albeit with worse efficiency. Even something as simple as a Stirling engine with forced circulation of the fluid works as a heat pump.
If you are referring to transcritical CO2 that is absolutely right. However you can't just use any pressure change in any gas, it would work but it would not be economically viable due to that inefficiency.
But they are much less efficient that electrical ones, adding even a small amount of electricity to the cycle (even if the primary energy is heat) can dramatically improve efficiency.
> Finding a high-efficiency thermoelectric material that works at normal temperatures and pressures is nearly as much of a Holy Grail as finding a high temperature superconductor.
No, TECs operates on a quirk related to semiconductor properties and are using electricity to move heat from one side to another but necessarily have resistance. Superconductors however are seeking zero electrical resistance. Current TECs produce 5x heat vs heat moved, and have a limited range of operation and a small range (30c) for the delta in heat between the two sides. I’ve been fascinated by TECs for years and I aspire to freeze CO2 with them, but it’s actually been really difficult to get cryogenic temperatures. You need to build a pyramid that has increasingly powerful TECs drawing heat away faster than it can accumulate. Even then I’m hitting walls in the -30c range because efficiency falls off a wall at both ends as you exceed the optimal ranges for the semiconductor materials.
> There are also heat pump cycles that can be driven directly with heat. Refrigerators based on that are relatively common here in Canada in areas without reliable grid electricity. Usually a propane or natural gas flame.
Notably, the propane fridges used in RVs (which AFAIK usually use ammonia for the refrigerant) are extremely inefficient. They have the huge upside of requiring very little electrical power to operate, but would never be my choice if I wasn't tightly limited on electrical power.
As you said: a Peltier heat pump is a purely electrical device, so if you're using a broader definition of the term, it could be a variety of different types of devices.
But that is the introductory paragraph, the author is defining what they mean by "heat pump": a device for heating a house which is powered by electricity. You could power it with something else, but the point is to replace natural gas furnaces.
My mind parses the term "heat pump" as a device that works on temperature by compressing some medium. Works out just fine for most heat pumps, but not at all for e.g. the Peltier element which is about moving heat from one side to the oher ("pump") but does not involve compression at all.
Hmm, as somebody who knew a bit about heat pumps but not much, I did find it added to clarify/distinguish between the main mode of operation of heat pump, used to accomplish the actual heat transfer; and what power / mechanism is used to move the mechanical bits.
I.e. an internal combustion engine implicitly uses some kind of burning fuel; if on the other hand you want to use electricity as energy source, it needs a different kind of engine entirely. But that, as I understand from the post, is not the case here - heat pump as described here can operate on same principle and look broadly similar in its core parts, whether powered by electricity or something else.
In 2017 we installed a very efficient air-source heat pump and solar panels. My electrical utility offers 1:1 buyback of electricity so I am able to build up a credit in the summer and run the heat pump well into the fall and winter on that surplus. The system is sized for cooling the house which means that it is undersized for heating, but during cool fall and spring temperatures it operates satisfactorily as a heat source.
Our fallback is the pre-existing gas boiler which is much simpler, more reliable and able to be powered by a small generator during our all-too-frequent power outages.
If I am still in this home when the current heat pump fails I will seriously consider a ground-source system instead. The ability to operate during an extended power outage is a significant concern and I expect to always retain the gas boiler as a backup.
I'll also have solar + battery. Should be able to run the furnace & fan but not the heat pump (too many kW/h) during a power outage and thus heating with gas. It'll run off the heat pump for 90-95% of the year, only using gas on the coldest days, or during an outage. To go full heat pump for 100% of the year you need to seriously upsize the heat pump(s) and you wouldn't have performance during an outage.
A wood pellet heater can be a fairly complex item, for a backup (depending on what usage frequency backup entails) a wood fired furnace might be more suitable if the owner is happy with having to add fuel every once in a while.
Myself, I would like a ground source system that lets me store in heat from an oil fired AGA, a wood burning furnace and water heater panels on the roof.
Still waiting for one of these people who rave about their heat pump system to actually rely on it full time without a backup. Most folks could barely afford to replace an existing furnace in a place that has all the fixtures installed, much less pay to install a second one based on different setup, and then pay for maintaining two systems on top of everything else. It is absurd to think that this is a plausible way forward for anyone other than the wealthy tech enthusiast. Same thing for induction stoves. You all should start a club or something.
The tech is not ready if you need a backup. I've lived in extreme cold climate areas and no gas furnace I've had has ever needed a backup.
I live in the snowy Great Lakes and I rely on a ground source heat pump and hot water heater full time. No issues at all. Cost similar to a high end gas furnace system when the tax credits were applied. Probably cheaper with air source systems today.
I live in the city and don't lose power, but I'm hoping to eventually use a EV as a battery backup when the equipment is available and standards are finalized.
A battery in a compact like the Chevy Bolt could power my heating system for several days.
It's not like modern gas furnaces don't require power to operate. In a recent Buffalo blizzard power went out and many people with gas heating still froze and had their pipes burst.
Define backup? I have a heat pump as my only source of cooling/heat, but it does have a single heat strip in it for the couple days a year it gets too cold for the heat pump alone. There no "second fixture" to maintain.
Its always funny reading such comments while others are running for years their heat pumps without any problems needing a backup.
Not only they are used in Scandinavia for years. Also in Germany they are used for years. The company Waterkotte operates since the 1980s in Germany and is a pioneer in this showing it is working.
Loads of countries have effective power grids which go down incredibly rarely. I can't even remember the last power cut I had - maybe a few years ago? It's certainly rare enough that I don't need my main source of cooking and heat to take it into account.
My parents live in rural Scotland and use a ground source heat pump for heat and an induction stove for cooking. Power outages happen more often - but still pretty rarely. If they do, they burn wood for heat and eat cold food for a few hours.
I’ve a 6kW nominal, ground-source heat pump as the only heat source. This is a well insulated building standing atop the soil of a European country with a temperate climate*. It does a great job at +35°C (passively cooling) and just as great at -35°C.
During installation we've even made a mistake and it heated the building up to something like +27°C inside during early winter all without breaking a sweat (or my wallet.)
The tech is ready. Many attempts to apply it is what’s getting botched.
* EDIT: having checked, most of europe falls within temperate – the country is up north.
The article is light on technical details, pointing to a heat pump vendor site for "proof" that they're great.
I live in a heavily populated area with high standard of living, and yet we have had power outages lasting up to a week in the years we've lived here. Almost all in the winter, but also some due to hurricanes. We have have solar, which is great in the summer heat, but not as wonderful in the winter. We have air source heat pump, but also oil furnace backup.
We normally run the heat pump when its above 35F, as the efficiency of the heat pumps drops like a rock below 40F and its just not worth running below 35F. The heat pump is not an ancient POS. It works great 99% of the time, but 1% of 365 is 3.65 days per year. Banking on "most of the time" to be alright all of the time is foolish.
We have diesel generator in case of power outage, which allows us to run the oil furnace using the same fuel as the furnace. This strategy has allowed us to ride through many 1% case scenarios without drama.
If gas remains expensive in Europe, it won't be absurd, so much as an economic no brainer to have a air to air heat pump, alongside a back up gas boiler. This should happen pretty quickly as renewables take off, and gas is no longer needed for electricity generation when the wind is blowing.
At some point a bit further on, the backup can be simple direct electric heating.
Wouldn't using a lake as a heat/cooling source cause "thermal pollution"? It's probably fine if a couple houses surrounding the lake use it, but if the technology begins mainstream enough to where everyone is using it, it could cause a lot of issues for the flora and fauna of that lake / downstream habitats.
I think in the winter it would be fine to move heat from the lake to houses but in the summer it's worse. We're already having problems with lakes being too hot in the summer which results in evaporation, algae build-up and less oxygen. This also promotes invasive species.
Of course, the question is at what scale we can build such systems and if that would raise water temperatures significantly.
I had a similar idea when I was designing a heating system for a mountain house I was planning on building. I was planning on primarily heating with an oversized wood stove. The excess heat the wood stove would produce would be captured by a heat pump inside the house with its coils in a 500 gallon tank of water that was well insulated. When the house needed heat you could run the heat pump in reverse or make a system that removed the insulation around the tank of water letting the heat out. I had a spreadsheet with the heat calculations. I think the water at 150F degrees had around a megawatt of energy stored in it and that could have heated the house for a couple weeks. I never ended building that house, but would love to build a system like this in the future.
If you have enough sufficiently dry wood, downdraft gasification models burn extremely cleanly (they're effectively rocket stoves), but those models require a fair bit of maintenance, especially if your wood is slightly wet or green, because soot can quickly build up on the water envelope.
I have about 1050 US gallons (4000 l) of water storage in my house. The very effective wooden carburettor heating system is heating up the water storage. Then you use the water storage for next days until you have to re-fire.
That is a standard package provided by many companies from Austria and Germany.
Readit News
Ducts are dead.
The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units including installation. Payback time is about 3 years. The system is oversized, but enables excellent zoning and of course provides cooling which is a must on 40C/104F days.
Why do they seem to be so much more expensive in the US?
And mistakes by installers will cost even more. Our installers didn't flare a line set connection properly and it leaked slowly and that was a very expensive bill (especially since refrigerants have changed so much).
Our Daikin indoor units have also had condensate leaking issues, probably due to poor installation.
Ductless heat pumps do seem like the future but I think there are issues with regards to condensate draining, air filtering, and indoor unit cleaning/maintenance and replacement that could be done much better.
Cleaning basically involves a dedicated cover + drain that diverts water to a bucket, and blasting it with what's effectively a "low power pressure washer" I can use indoors (carefully), and "Lemocide" to properly disinfect... And coil cleaner for the fins. Takes me a good 4+ hours per unit, largely spent preparing the area in case there is any rogue spray. (Though TBH I may be a bit obsessive about getting it right.)
I also had a drain leak as you mentioned -- blasting the drain line with aforementioned "low pressure washer" helped with that. Still a bit gross to deal with. (And learning how to properly disassemble and clean the drip tray is the final thing I've put off leaning for a completely-thorough deep clean... I'm a bit horrified anticipating what I'll find...)
I once looked at a house with a new GSHP horizontal loop installed in the desert southwest US. I talked to the installer and they said the loop was only 12” deep. There’s no way the ground maintains steady temp at that depth, meaning you’re losing efficiency in the hot months when you need it most. Not to mention thermal pollution which will exacerbate the problem and the risk of hitting the loop with even minor ground work. They were adamant it was a good design.
Unfortunately, many installers jump on the bandwagon without the necessary expertise.
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Ducts are still needed to circulate air, especially if you want to remove stale air (e.g., bathrooms, kitchen) and bring in (filtered) fresh air (to bedrooms).
I have a CO2 detector that I believe is a reasonable proxy for stale air. When it goes above 1000 I simply open the windows. By the time I remember to close the windows the reading is almost always below 500.
https://www.buildwithrise.com/stories/ductless-heat-recovery
It's really a very good proposition. Has all of the advantages of central heating and the efficiencies the heat pumps
Heat pumps need to be scaled for the maximum heating or cooling load, whichever is greater. The optimal situation is that the heating and cooling loads are similar, but in colder parts of the U.S. the heating load is much larger than the cooling load and the case for the heat pump is not so good as a place where the need for heating and cooling are more balanced.
When it's really cold out (say 25F or below), the heat pump stops for around 10mins to defrost the exterior coils, which means no heat running at all in that period, and this pause happens more frequently the colder it's outside. The end result, our ~1400 sq place took more than 24hrs to heat up from 55F to 72F when we got back after christmas.
Also you don't save any money on operating it, even with the efficiency yade yada the cost of electricity will run you more than the equivalent in nat gas. So nothing but downside.
Great. You just eliminated approximately 15% of lazy screenwriter tropes for thrillers and action movies. Now they are forced to rely on replacing live surveillance camera feeds with a loop.
If you went with a common US brand you can get a good system with 4 units and a 36,000 BTU heat pump unit for around $6,500 USD installed.
I don't love the wall units - they're pretty ugly, even the new ones. If you're getting a mini-split, the in-ceiling or wall cassettes that are hidden are really the way to go IMO.
Same, and we have just implemented 2 x 7.1kw units along with about 7kwh solar panels. Our heating costs have plummeted and we can survive on days like today (17th Jan) with minimal impact to our comfort.
We are looking at changing water heating next as this is now the biggest part of our utility usage.
They're pretty quiet, too. You can certainly hear the air coming out, but it's fairly quiet and certainly wouldn't be noisy enough to bother you over tv, work, or anything else.
Ducted heatpumps are a thing here in NZ and make sense to me, not that I have used one. The heatpump sits in the roof and air is pushed into three or so rooms through ducts.
If building a new house I think ducts would be the way to go.
Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency.
Here is just one article on it: https://newenergythinking.com/2018/10/20/dont-use-ducts/
We have a two-level, five bedroom new build in Auckland which came with a single-zone ducted system. So outputs are the bedrooms plus upstairs and downstairs lounges. The vents are tidy and unobtrusive - much less space than a wall unit in each location.
We're having major issues balancing the temperature across the different rooms as there is one thermostat.
Think setting the temperature overnight for one room with a couple plus a cat vs another room with one of the kids. Basically the wife and I are always far too hot because otherwise we're freezing all the other rooms. Or setting a reasonable temperature in the lounge makes all the rooms icy in short time.
I'm now thinking about forking out the couple of thousand to get a small heat pump installed directly into our room so we can run it separately from the rest of the house.
So if building from scratch, either look into a multi-zone system or separate heatpumps. If you can get separate systems but hidden in the walls/roof that would be the best.
Another great thing about having three seperate units is if one breaks, rare as it is, you're not stuck without heating / cooling.
I despair for the rental market right now. High prices and landlords are generally crap at amenities they don't personally use.
How do you move the heated/cooled air into/around the house without ducts?
So people COMMONLY wind up with unbalanced floors, and people typically try to fix it by adjusting the vent register opening with mixed success.
Part of the problem is that the thermostat is biased to wherever it is located. You can get systems with remote add-on temperature sensors, but that doesn't by itself adjust where heat/cold is being sent through a ducted system.
The great thing about a Mini-Split is that you're, at minimum, heating each floor independently with its own thermostat. You can then put in e.g. interior door vents that simply let air pass between common areas and the rooms when the doors are closed.
This can go even further with for example two Air Handlers per floor (quad units) on the east and west. So that as the sun moves, the correct level of adjustment can be applied to only the side of the floor that needs it.
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Installing good insulation is also really important even if you're not using heat pumps! With bad insulation, you're wasting energy no matter what technology you're using.
Also insulating an old home (pre-WW2) could begin to introduce moisture issues in the walls that weren’t there the last 100+ years since the leakiness of the home would dry the structure. Last thing you want is for condensation and water vapor to build up in the insulation and then begin to rot the wood. Modern build have vapor barriers and airtight seals.
I guess my point is to be careful with old structures without considering things. They were built the way they were because those were the materials we had (old growth wood!) and they were designed to function a certain way.
In Denmark, this was solved by adding a second, modern window on the inside. The outside kept the same look, and it is even more insulating than a single modern window. Is it a bit clunky to have to open two windows ? Sure. But it is better than not having insulated windows, or ruining the appearance of cities.
[1] https://amp.theguardian.com/environment/2023/jan/01/rebound-...
But it's not like heat pumps stop working because of your insulation. They just get more costly to operate. And especially the smaller systems can only deliver so much energy to your house. Basically, if you multiply the maximum output by three, that should be above whatever you are currently using to heat your house during a really cold month. If it's lower, it's not big enough.
This hermetically sealed environment that we create for ourselves is bad for us.
Side note: As a US resident in an area with a ton of mosquitos, I cannot understand why other countries don't heavily use window screens. Lizards a pretty cool, flies and other flying bugs are just annoying and gross.
1. https://en.wikipedia.org/wiki/Energy_recovery_ventilation
Some might say it's the defining feature and purpose of having shelter is that we don't live at the mercy of the weather.
I can't run a business with indoor temps from 24-31c during business hours. Compounding loss of brain function outside of 18-23c is found by every study I've read.
The less exposure to particulate pollution and extreme temperature, the healthier you are, I can't see any arguments otherwise.
That's a feature not a bug.
> This hermetically sealed environment that we create for ourselves is bad for us.
Not at all. Heat recovery vents exist for a reason!
When it’s freezing cold outside, it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated.
Someone needs to make a standard for moving heat/cool through all appliances in a house…
The fridge is simply moving a little of the warmth in your room out of its box, and adding a little more warmth to the room in the process. You lose no heat from the room, which is what matters, really. It would be worse to dump the heat outside! At least in winter. The heat has to be removed in summer if you have air conditioning.
In any case, an exterior heat exchanger and heat pump that can handle a wide exterior temperature is much more heavy duty. This could all end up being less efficient, in practice. House-scale heat pumps can efficiently move heat even from a freezing cold outside into a warm interior. Just as fridges can efficiently move heat from their cold interiors to a warm room.
Voila: everyone has heat pump heating! (And dead compressors).
The dumb thing is having the compressor itself indoors in summer. Should be outside.
I often see my HVAC cooling when the set-point temperature is actually _higher_ than the outside temperature. Logically, the house is a heat generator, it makes sense physically. The roof is black, etc.
It would offer a good number of benefits if the system could outright open a duct to the outdoor air, and suck it in whenever the local outside temperature is within the range requested by the user. People who are into optimizing energy use (they exist) can go even further and pre-cool their house during the night in summer.
For this to work, all you need a pusher fan, no refrigeration at all. There might be some pressurization problems, like, you may need a duct both for the intake and outlet. Also might require another filter... but air quality would improve significantly.
This is a really "dumb" idea, but it's perfectly in-line with all the new ideas being thrown out there. The new ideas just tend to throw in an additional heat storage mechanism, like a water tank (in the article). You can get a lot more efficiency gains by saving the night's cold in a tank and using it through the day. But on a more basic level, you can pump straight into the house when the conditions are right.
The idea of doing the same in my home has been taunting me for years now. Ideally you'd have two such louvres, one with a push fan in the upper floor and the other with a pull fan in the lower floor to simultaneously eject unwanted heat, bring in fresh air, and boost whole-house circulation. They'd be set up to interface with the thermostat/hvac and would operate when the outdoor temperature at intake is lower than the temperature at exhaust and both are above the set point on the ac.
The biggest problem is really one of convenience. You'd need a filter on the intake and a rather large and powerful fan to overcome that static pressure - ergo, a noisy one. And you'd probably have to fully dismantle the system in the winter to prevent the cold from getting in (the Midwest is cursed with both hot and humid summers and cold and dry winters). It just end up being the kind of thing where the devil really is in the details and you either do it right and it's a huge undertaking or you do it fast and sloppy and its drawbacks won't be worth it.
But I agree, nothing is more infuriating than seeing the AC on and the outdoor air temperature being lower than that of the home. And opening windows just doesn't make a difference since in most 20th century homes there's just poor airflow and no circulation.
My thought is I should keep them closed due to extra load on the AC to dehumidify the outside air. Or open windows and turn AC to fan-only mode to prevent stagnant air in rooms without windows.
Most of these systems have a damper that the system can use to choose how much fresh air is used or how much return air is recirculated so it’s not difficult to use that to just put fresh air in directly with no cooling or heating. Even systems with heat or energy recovery will often have a bypass damper.
You need the humidity to be in the right range as well as the temperature, but it can save a lot of energy!
1) Long refrigerant pipes. This is unacceptable because it increases the amount of refrigerant in the systems (refereed to as the charge of the refrigerant). Refrigerants are powerful greenhouse gases so it is important to design low charge systems.
2) Another process fluid (e.g. water or glycol). This adds expense (more pumps and heat exchangers). You'd increase the cost of all these systems by a lot.
Also, both 1 and 2 involve running a new set of single use pipes around your house.
3) Make a "single appliance" household. A design like this has been tried - single AC/heat pump hooked to fridge, freezer, oven, dishwasher, washer/dryer, and water heater. The problem is that you really have do design the house around this and it is quite limiting from an architectural perspective.
Combined AC/heat pump and water heater is a thing though.
Air-sourced exchanger individual appliances are just so much simpler for the consumer.
Not dissing ground-source heat pumps. Those are fine, since they are typically a plumb-once-and-done. You just generally don't want separate appliances which quick-connect.
At large scale (think like walk-in coolers of supermarkets), this is actually being done in the form of district cooling [1].
> Someone needs to make a standard for moving heat/cool through all appliances in a house…
The problem is that the piping itself and the circulation required are sources of energy loss, and it's hard enough to keep these appliances sealed so they don't leak their coolant - most coolants have insane CO2 equivalent potentials. It's not worth the effort.
[1] https://en.wikipedia.org/wiki/District_cooling
For something the size of a home fridge the costs would be immense compared to the energy savings. You're far far better off spending that money on more efficient heat pumps and more/better insulation.
The federal limit for the amount of power a fridge can pull is 527 kWh/year, which at my rates (admittedly on the low end these days) is ~$70/year. There are very commonly available fridges that are < 300 kWh/year, which would be ~< $40/year. So before even taking into account the efficiencies you implicitly make back when you're heating your house anyway, that's your per-attached-appliance limit for input cost on building out, maintaining and running that system.
Though, I admit that the idea of a completely silent fridge & A/C is alluring. Here's to hoping we make some breakthroughs on sold-state heat pumps.
It was never pursued further for reasons I discussed in another comment on this thread.
They move the heat from inside the fridge to outside. That heats up your home. This reduces your need to heat your home, temporarily.
Generally, every device in your home that uses electricity is creating roughly the same amount of heat as an electric heater would have using the same amount of electricity. Even fridges and freezers, so long as nothing is being vented outside.
Keeping a big reservoir warm for the sake of keeping it warm only becomes efficient with regular usage.
However unless the house was built, and / or the pool installed in a coincidentally fortunate configuration where the AC compressor and the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
that makes no sense. effective insulation is no problem at all. In large parts of europe they even have centralized water heating and run insulated hotwater pipes to houses across kilometers without huge losses, hell, for this kind of setup it would even be possible to just run refridgerant, which typically specs at ~15m for minisplits as maximum(with very minor losses) distance
Not really, efficienty aside the heat it puts out the back is coming from inside the fridge... Which is coming from the room housing the fridge. So over the course of a day it should be neutral.
Installing ducts, etc. might take more energy than is consumed over the product life-cycle.
It would add other limitations, such as only being able to put fridges next to exterior wall.
Or most likely it'll add additional installation cost. Money perhaps better spent insulating your house better.
You'd have fewer compatible vendors to choose from. Less competition.
Flexibility is probably way more important than micro optimizations.
It can be implemented as a single line of force water flow with 20-25 Celsius. It is viable as both a heat source and a heat sink at the same time.
This thing can be connected to both your coolers and heaters, and thus transfere heat from one to another. Maybe you could even get you desktop computer into the loop.
Usually it implemented on a lager scale, but i don't see why this would work scaled down.
It should net out to no less than the same energy though, right? That refrigerator needs energy to move the heat out of the fridge and into the home. If that process takes more energy than just letting the house HVAC deal with it, wouldn’t the energy bill be higher?
https://bayes.wustl.edu/etj/articles/AJP00180.pdf
Just to be pedantic, but not exactly. The typical design in a domestic heating unit, or refrigerator is mechanical. A fluid is pumped and cyclically compressed/expanded. While electric motors are usually used, they can be driven by any source of mechanical energy; driven directly by a combustion engine is not too unusual.
There are also heat pump cycles that can be driven directly with heat. Refrigerators based on that are relatively common here in Canada in areas without reliable grid electricity. Usually a propane or natural gas flame.
Thermoelectric coolers are actual electric heat pumps; directly moving heat across a semiconductor junction. Not very efficient and quite expensive practically. They're used in those USB drink coolers and to cool down lab equipment. Finding a high-efficiency thermoelectric material that works at normal temperatures and pressures is nearly as much of a Holy Grail as finding a high temperature superconductor.
They are called https://en.wikipedia.org/wiki/Absorption_heat_pump
But they are much less efficient that electrical ones, adding even a small amount of electricity to the cycle (even if the primary energy is heat) can dramatically improve efficiency.
Are they two sides of the same problem?
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Notably, the propane fridges used in RVs (which AFAIK usually use ammonia for the refrigerant) are extremely inefficient. They have the huge upside of requiring very little electrical power to operate, but would never be my choice if I wasn't tightly limited on electrical power.
But that is the introductory paragraph, the author is defining what they mean by "heat pump": a device for heating a house which is powered by electricity. You could power it with something else, but the point is to replace natural gas furnaces.
I.e. an internal combustion engine implicitly uses some kind of burning fuel; if on the other hand you want to use electricity as energy source, it needs a different kind of engine entirely. But that, as I understand from the post, is not the case here - heat pump as described here can operate on same principle and look broadly similar in its core parts, whether powered by electricity or something else.
Our fallback is the pre-existing gas boiler which is much simpler, more reliable and able to be powered by a small generator during our all-too-frequent power outages.
If I am still in this home when the current heat pump fails I will seriously consider a ground-source system instead. The ability to operate during an extended power outage is a significant concern and I expect to always retain the gas boiler as a backup.
I'll also have solar + battery. Should be able to run the furnace & fan but not the heat pump (too many kW/h) during a power outage and thus heating with gas. It'll run off the heat pump for 90-95% of the year, only using gas on the coldest days, or during an outage. To go full heat pump for 100% of the year you need to seriously upsize the heat pump(s) and you wouldn't have performance during an outage.
I guess it depends if your natgas bill has a big fixed cost (and I guess you’ve already covered the sunk cost of connection…)
Myself, I would like a ground source system that lets me store in heat from an oil fired AGA, a wood burning furnace and water heater panels on the roof.
The tech is not ready if you need a backup. I've lived in extreme cold climate areas and no gas furnace I've had has ever needed a backup.
I live in the city and don't lose power, but I'm hoping to eventually use a EV as a battery backup when the equipment is available and standards are finalized.
A battery in a compact like the Chevy Bolt could power my heating system for several days.
It's not like modern gas furnaces don't require power to operate. In a recent Buffalo blizzard power went out and many people with gas heating still froze and had their pipes burst.
Eh? Most new houses in Ireland have them these days (it's more or less the only way to meet the efficiency requirements). There's never a backup.
> Same thing for induction stoves.
Eh? Again, these are pretty standard these days, and why would you need a backup?
This is common for my area.
Not only they are used in Scandinavia for years. Also in Germany they are used for years. The company Waterkotte operates since the 1980s in Germany and is a pioneer in this showing it is working.
But there are always people ignoring the facts.
My parents live in rural Scotland and use a ground source heat pump for heat and an induction stove for cooking. Power outages happen more often - but still pretty rarely. If they do, they burn wood for heat and eat cold food for a few hours.
During installation we've even made a mistake and it heated the building up to something like +27°C inside during early winter all without breaking a sweat (or my wallet.)
The tech is ready. Many attempts to apply it is what’s getting botched.
* EDIT: having checked, most of europe falls within temperate – the country is up north.
I live in a heavily populated area with high standard of living, and yet we have had power outages lasting up to a week in the years we've lived here. Almost all in the winter, but also some due to hurricanes. We have have solar, which is great in the summer heat, but not as wonderful in the winter. We have air source heat pump, but also oil furnace backup.
We normally run the heat pump when its above 35F, as the efficiency of the heat pumps drops like a rock below 40F and its just not worth running below 35F. The heat pump is not an ancient POS. It works great 99% of the time, but 1% of 365 is 3.65 days per year. Banking on "most of the time" to be alright all of the time is foolish.
We have diesel generator in case of power outage, which allows us to run the oil furnace using the same fuel as the furnace. This strategy has allowed us to ride through many 1% case scenarios without drama.
At some point a bit further on, the backup can be simple direct electric heating.
Of course, the question is at what scale we can build such systems and if that would raise water temperatures significantly.
I am not a biologist.
https://en.wikipedia.org/wiki/Outdoor_wood-fired_boiler
If you have enough sufficiently dry wood, downdraft gasification models burn extremely cleanly (they're effectively rocket stoves), but those models require a fair bit of maintenance, especially if your wood is slightly wet or green, because soot can quickly build up on the water envelope.
That is a standard package provided by many companies from Austria and Germany.
[1] https://news.ycombinator.com/item?id=34233719