Heat pumps, more than you wanted to know (2023)
calv.info
calv.info
Are you in a cold climate? My biggest concern is installing splits in very cold mountain climates (my use case).
P.S. previous comment with example specs: https://news.ycombinator.com/item?id=38266032
Living in a cold mountain climate you probably have a pretty decent insulation.
The thing I don't like about MrCool is that you can't cut the lineset and have to coil the extra which is a bit janky. Also they have a considerable markup over other DIY.
I went with mrcooldiy and did it myself for about $7k.
Sorry, could you try that again? I cannot figure out what you meant.
Coolth escapes in, particularly from the floor
Coolth is the antonym of warmth.
Everything was off the shelf — the new systems are crazy better than just a few years ago.
I wish that weren't the case.
(Our overall experience with them has been very positive).
And then there's the availability of the part/unit which drives price.
Physical work is underappreciated.
It’s not how it “should be”, but that’s how the economics have shaken out. Paying a tech windshield time and working time (probably twice) and finding/waiting on the proprietary parts is a losing game. If it works 30 days, it’s probably going to work 8-12 years.
Everyone: just watch this to start your journey.
Heat always flows from a high temperature to a low temperature. However, we want heat to go the opposite way (i.e. from the cold outside to our warm houses). There's a technique to do this. We use a gas (the refrigerant) to transfer heat.
We first expand the gas (which cools it) until it cools below the cold outside. We then bring it near the cold outside where it now starts absorbing heat until it matches the cold outside temperature. We then move the gas and compress it until it's temperature matches/exceeds our desired warm inside temperature. Then, we bring it to the warm indoors where heat will now flow out of it.
During the entire cycle, the gas is inside a closed loop. It exchanges heat through radiators. The compression & expansion cycles uses energy (technically they can be offset against each other a bit) which is added to the gas (conservation of energy) raising its temperature.
Thus by supplying a little electricity, we're able to move heat from the cold outdoors to the warm indoors. The high efficiencies are because for using X units of energy, we're able to heat the house by X+Y units where Y is the heat transferred from the outside. Typically Y >> X.
To raise the temperature of my 300 square feet room by one degree I need the same amount of energy, no matter the source. But the ways of delivering that energy aren't the same.
If I have a simple gas burner, I need to know how much gas do I have to burn to heat my room. It will keep me warm, but it's not a good idea. Burning gas with a flame makes other gases that I don't want inside. I need to vent them, but I will lose some heat through that.
I can also get a gas furnace that condenses those byproduct gasses in a second heat exchanger for extra efficiency. Maybe seal it up better too. It needs a little electric power for ignition, so I need to take that into account. But overall, it would be more efficient. I would need less gas to heat my room.
Even though I'm using gas in both examples, the efficiency is different. It depends on how I convert that gas into heat.
I can also burn that gas in a generator to produce electric power. Then I can use that electric power for a resistive heater. Not a great idea, but it's an option.
I don't have to burn the gas myself. I can delegate generating power to a gas-fired power plant and buy power from them. And I can use a heat pump instead of a resistive heater. My heat pump will use less power than a resistive heater, so that's good, I suppose.
The question remains: how much gas do I (or a power plant) have to burn to heat my room. The answer depends on what do I use the gas for and how. That's the efficiency.
By burning oil or converting electricity to heat, 1 joule of stored chemical or electrical energy converted to heat energy will raise the heat of that something by a maximum of 1 joule. A maximum of 100% efficiency.
By using 1 joule of energy to compress cold gas into warm gas, we can raise the heat of that something by 3-4 joules. Moving heat energy around is more efficient that generating heat energy. Commercially available technology 300%-400% efficient.
This isn't correct. Here's a thought experiment to clarify:
If we burn X MJ of oil, we transfer X MJ of energy as heat to our house.
Otoh, if we set up a generator (say 40% efficient) which produces electricity from oil and dumps waste heat into our house, and use that to power a 300% efficient heat pump, we get 0.6X (generator waste heat) + 1.2X (300% * 0.4X) = 1.8X MJ of heat using the same X MJ of oil.
Thus,we get an additional 0.8X MJ of heat (80% extra heating) from the same X MJ of oil just by using a heat pump (& generator) compared to burning it. I.e we're using the energy stored inside the oil more efficiently.
In Sweden the hardware cost around $1k - $2.5k and installation $500 - $1000. It's not a complicated task.
Geothermal heating on the other hand cost around $15k - $20k.
Most people I know have one of these, direct electricity to heat is not really an option.
labor costs are absurd
In the US, it’s more common to have 1 or 2 large units pumping into ducts in every room of the house.
Speaking about the UK (article is mostly about he US which will have their own problems), we have very poor quality housing stock with effectively zero insulation. You hold your hand to the exterior walls of your typical 2-3 bedroom terrace house (the most common type of home in the UK) in the winter and its just ice cold. For these homes the exterior wall are just solid brick and plaster with no air gaps. Many homes still don't have double glazing and their windows bleed even more heat. These homes go cold quickly when you turn off a gas boiler, and a heat pump just cannot keep up with the heat loss.
In addition large numbers of households in the UK have migrated to "combiboilers" heating systems that dispensed with hot water tanks for on demand hot water from their gas boiler. In the process many of these properties have converted the space previously designated for hot water storage to loft extensions or other home upgrades. UK homes are pretty small, and going to a heat pump system means going back to hot water storage, which most UK homes have no space for without costly changes to the home layout/structure potentially including sacrificing parts of precious loft conversions.
Frankly we might be better off just knocking down and rebuilding some of our housing stock at higher densities such is the cost of retrofitting and our housing shortages, but there is no political appetite in the UK for any radical solutions like that.
Gas was cheap so nobody cared. Just turn up that dial!
Modern houses and apartments are marvels of engineering though.
EDIT: ok so the best interpretation I have is that it has just been so cheap with gas that people have not bothered insulating their houses.
The UK government back in 2010 actually had major plans for nation wide insulation, but famously the prime minster at the time, David Cameron, ordered the cutting of "the green crap" (widely reported to be his words) to help resolve some short term political problems with the budget in the early 2010s.
A heat pump’s max output in heating mode decreases when the outside temperatures are low enough (whereas a gas boiler has a roughly constant max output and it’s quite inexpensive to size a wall-hung combi for 150K BTU/hr [44 kW] if needed).
Buildings that are fine on the coldest design day with a gas boiler may need more output than a heat pump can provide on that day.
Adding insulation can reduce this gap, which is why you’ll often find a heat pump project needs insulation, while a boiler replacement like-for-like would merely benefit from additional insulation.
So technically it would be possible to install a heat pump with the same capacity as the existing gas boiler, but it would costs a ton more and it would all be upfront.
Indeed. However a first step would be to put in decent building regs so that sub par new houses aren't being built! Still waiting for the new regs that were originally started in the planning back in 2006 or so.
I cannot find the source atm, but I recall that the government advice to builders is against installing ventilation systems to discourage retrofitting them in future for air conidtioning, which is makes it even harder to retrofit for heat pumps.
Insanity!
WTF? We're going to need air conditioning! We definitely need heat recovery ventilation if we're going to have proper insulation.
Not to mention that it's starting to look like "minisplit" reverse aircon might be one of the more economical forms of heatpump.
However they also don't encourage passive cooling or low cost active solutions either such have making sure building have pass throughs for airflow, shading of windows, or fan systems. Government seems to be forgetting that current projections have us with Madrid style weather in the next 30 years and we will all be waving our fists.
https://www.thebureauinvestigates.com/stories/2023-12-05/sti...
Partly through poor design of new builds.
To expand upon this, consider an urban street like this: https://maps.app.goo.gl/A4HSZ2TFiJ2PyiAZ8
Beautiful houses with period features, in a great location. Big, traditional sash windows that let in loads of light. An L-shaped layout giving lots of natural light in all rooms. High ceilings. Market price about £2 million https://www.rightmove.co.uk/properties/139018139#/?channel=R... (admittedly being in London pushes prices up a lot - but the point is, these are desirable properties)
The walls are all solid brick, no cavity and no insulation. The L shaped layout means a lot of external wall area, and the big windows don't help either. High ceilings make it even harder to heat. Many of these properties are prone to damp problems if they don't get enough fresh air circulating. You can't add external insulation without covering up the period features. Obviously you can insulate the loft and install double glazing - most of them will already have done so.
It turns out nobody wants a £2000/year heating bill - but also, nobody wants to knock down and rebuild a £2M house over a £2000/year heating bill.
The reality is that it is actually a bit shit. and would cost tens of thousands to retrofit. The compromises that the owners would have to make in terms of either apperance or internal area make heat pumps very unattractive.
The main issue is to add insultation you either do exterior insulation which covers up all of the period features that make the property valuable in the first place (and could lead to complaints from neighbours) and for many terrace houses the space between the front of property and the public street is 0, or you give up interior floor space which even at this price point is actually pretty small already. Both lower the value of the home which for most British people is the primary and often only investment (UK financialisation of housing).
The thing is, heat pumps aren't a particularly good deal right now.
Heat pumps generally have less heat output than a gas boiler, so it won't make your house any warmer.
Even taking government subsidies into account, the installation costs are several times higher than a gas boiler, both for the unit and often requiring new radiators and suchlike.
And typical energy prices in the UK might be 6.5p/kWh for gas, 26.0p/kWh for electricity - so even if your heat pump achieves a 3.0 CoP your running costs are still higher. In the UK, the months when you'll want the most heating are the months when domestic solar output will be at its lowest. To make savings you've got to switch to a plan where electricity costs change several times a day, such as https://octopus.energy/smart/cosy-octopus/ and not run your heating between 16:00 - 19:00. This makes a well-insulated home even more important.
And you might think you're going to save money by not paying the gas supply 'standing charge' - but gas suppliers can charge whatever they like to remove your meter. If they say it's £1500 to remove your gas meter and save you 30p/day - you're probably not going to be saving 30p/day
So it's less a case of "investing" in the house, and more a case of "investing" in good karma by helping the environment.
You can get electricity at 7.5pkWh. With a battery, I get 12h of cheap electricity per day, and the rest at higher prices.
At the coldest time of the year, I'm getting an average of 20pkWh.
This is just a fraction above break even gas/electric.
The rest of the year its no contest, heat pump wins.
My energy usage for heating is down by 60% year on year
My bills are the same as they were 3 years ago.
You need a smart meter. It's electricity only.
You (and I) get £50 credit with this link: https://share.octopus.energy/happy-frog-559
Of course these figures depend on how much of the day the house is occupied, how high the thermostat is set, and how cold the weather is.
[1] https://find-energy-certificate.service.gov.uk/energy-certif...
(1) This is what Americans would call a "row house", and IIRC in the UK is called "terraced housing", which has the huge benefits for all but the ends of the rows that your side walls (the longest walls of the house) are insulated by ... your neighbor's house. So, although the architectural features you mention are indeed drawbacks, their impact is significantly reduced by being in a row of connected houses. It's the single-family/full-detached houses that suffer from these problems more fully.
(2) I don't see the L-shape at all.
The original design on these Victorian terraces is typically an L shape, where the upright of the L had the kitchen in it, and the base of the L is the main block of the house. This allows the room at the back of the main block to have a window facing back into the garden for light. Many have subsequently been extended for extra space and to add bathrooms, which were not originally present. Partially or completely filling in the corner of the L is popular.
I am extremely familiar with this shape - my sister lives in one just like this in Walthamstow (prolly not worth 2M yet though).
That design of terrace is exceptionally common in the UK, where each pair of houses is mirrored, with a kitchen out the back and a side passage letting light into the middle room on each level.
How do you know that? Perhaps just from "Victorian", but I think it would help if estate agents were required to list some basic facts about the house — the year it was built, the basic materials for the walls and roof, the type of heating installed.
Statistics on insulation for British dwellings:
- double glazing in 87.5%
- wall insulation of some sort 49%
- loft insulation 39%
https://www.statista.com/statistics/292265/insulation-in-dwe...
There are actually very few enforced rules about house listings. The market is pretty unregulated. However that house has an epc of C which would suggest its not insulated beyond maybe roof insulation or else isn't well insulated. To get a B or above you need to have a reasonable amount of insulation that you mostly only see in new build properties.
Glad you asked! For a start, as you say, it's Victorian.
For further confirmation, zoom in on the buildings with exposed red bricks and you'll see they're in a Flemish bond pattern, which only appears on solid walls. It's not new enough to have a fake Flemish bond pattern for decorative purposes.
You can also see at roof level, the party wall extends above the slates. Where it's unpainted, it's visibly two bricks thick.
If you can get into the house, you can usually tell from how thick the walls are. On houses with cavity walls, sometimes you can remove the skirting board going through an external door and look into the cavity.
You can also check externally for weep holes, the telltale signs of cavity insulation having been installed, and whether there's a damp proof course.
If you have friends in the area, they'll probably be able to tell you. If you get a survey done (which might be reasonable on a house of this age) they'll probably also be able to tell you. Often the homeowner will know too.
If you get cavity wall insulation installed, they'll drill a hole in the wall to check the cavity with a borescope and take a photo. It's a condition for getting the government grant that they confirm you don't already have cavity wall insulation.
> I think it would help if estate agents were required to list some basic facts about the house — the year it was built, the basic materials for the walls and roof, the type of heating installed.
If you check the 'energy performance certificate' (EPC) it should tell you about the insulation and heating. Of course, the qualifications to do EPCs are minimal so they don't really tell you any more than you can figure out from a house viewing. And estate agents often don't deign to produce the EPC until the house is already sold.
For this house, the EPC is https://find-energy-certificate.service.gov.uk/energy-certif... and states the walls are "Solid brick, as built, no insulation (assumed)"
The land registry's title plan will tell you when it was built for about three quid.
The EPC has the overview I was expecting. I had expected this to be linked from the estate agent's site, and didn't realise there was a place to search for them. (I no longer live in Britain.)
The opposite is now becoming more true: with heat waves that seem to occur more often, you want to keep the heat out and the cold in in the summer.
One of my neighbours redid all the insulation of their house and lowered the high point of the south-facing living room by 10-15C (and made the house much easier to heat in the winter, they can now get by on just the fireplace).
An other good option if you have the space (and money), especially with a south-facing living room, is to add a "sacrificial" sunroom (/ enclosed patio): at the cost of a bit of light, you get extra living space in spring and autumn, and the sunroom will insulate the living room in winter and summer (for the latter especially if it has an opaque roof e.g. tiling).
The central heating is still there and used sometimes, but I installed mini-split reverse cycle air conditioners in each apartment and they work great, you just have to size them (power wise) correctly. They were 550-700 euros each installed. It's much much cheaper to pay for electricity than the equivalent amount of wood, even after the cost of the units. There are various additional benefits like being able to use the aircons when it's briefly cold, or you just want to warm up the space a bit. You also get cooling for no additional charge of course.
Mini split systems are not always the best solution, but they are another useful option to be weighed against larger central heat pump systems. All depends on the situation, but heat pumps are the present and future, nothing else makes sense.
The split of cavity to solid walls is pretty even in the UK. There are gov grants available for insulation, both for walls and loft. It is true that many houses have moved to a combi-boiler and lost their hot water cylinder but cylinders are smaller than they used to be and personally I would guess the number of converted lofts in these cases is relatively small.
https://www.checkatrade.com/blog/cost-guides/air-source-heat...
https://www.gov.uk/apply-great-british-insulation-scheme
The main problem with an ASHP for your typical 2-3 bedroom terrace house is there is very limited outside space to put the thing.
Why not a tankless water heater? They are quite compact, and can be powered by gas or electricity. Are they just not really a thing in the UK?
But, it's also a fact that the US is far behind when it comes to heat pumps and energy efficient homes. The general knowledge in the US about heat pumps is terrible.
The main issue seems to be that installation is extremely expensive. Less expensive heat pumps are now available here if you are able to do the installation yourself, but installers will only work with the expensive brands they know. They are usually overbooked, and thus have no incentive to lower their prices.
The question would be what it would take to get competition in the market at the installer level. Any idea how this was accomplished in Norway?
I've just bought a big heat pump in Stockholm, this model from Nibe, which the guy installing it told me is one of the best: https://www.nibe.eu/sv-se/produkter/varmepumpar/franluftsvar...
It warms the whole house via floor heating (IIUC it's hot water circulating) and also ventilates almost all rooms (but that seems to be only for keeping the air in the house clean - it "pulls" instead of blowing warm air or something like that).
It cost me a total of 130,000SEK, which is 12,0000 USD (as I write this). Approx. half for the unit and half for installation costs. I don't have the geothermal option where I live because it's a water reserve, but that would be much more expensive, I expect at least twice as much.
I didn't buy a cheap unit, there was a cheaper model that they offered for a total cost of 80,000 SEK... but still, where could've I gotten this for 20,000 SEK :D
One well placed air/air can reduce the need for direct electricity heating a lot, even though some might be needed to assist in a bedroom or so.
My parents installed a air/air unit in the middle of the house (180kvm) for $2.5k this summer and it keeps the whole house heated except one bedroom that needs some assistance from a radiator.
It looks pretty good too... you need to do some cutouts for the warming pipes underneath, there's lots of Youtube videos showing how :D
But luckily, my floor heating apparently is still in very good condition so it will be a while before I have to replace that.
The main problem I've found is now that it's getting old and having problems there's nobody in my area that knows how to maintain them, they only install and then suggest buying a new one when the old one needs new parts, which is frustrating and in line with most white goods these days. So advice for the future is that forums like byggahus.se are good for advice on trouble shooting & parts replacements once it gets old enough to have problems.
These numbers must be for an air to air mini-split unit with one air handler with nearby electricity, $500-$1000 is 4-8 hours of labor. That’s not nearly enough for an entire home.
A whole house heat pump with heat exchanger costs substantially more, both in equipment and labor.
Heat pumps are a gimmick for rich people that already have well insulated modern homes. For everyone else it is vastly more expensive than gas or oil and in addition, we have to pay taxes for all the subsidies going to those rich people.
time will tell if I will get a return on my investment, the big question will be how long my heat pump is going to last
However to totally replace your entire heating needs with an all-in-one system is much more complicated than that. The heat pump I have alone in Scandinavia costs roughly $6-10k. That's powering water heating in every room plus hot water in the taps, zero additonal heating of air or water required. It's the size of bulky floor to ceiling fridge and does wonders for my electricity bill!
If I replaced wood pellet boiler I use right now with a heat pump I'd break even in about 20 years, which is longer than the expected service life of the pump..
If it was indeed a question of insulation or airtightness, then perhaps spending a part of that money for renovations in that area and only then a fraction of the price for a reasonably-sized heating unit might be sensible. You could also do just the renovations and thus reduce your wood pellet usage substantially as well – already a big win for the environment.
That aside what I wanted to point out is that because of heat pump pricing they are currently not the best choice, economically speaking. It is 6-10x more expensive upfront and won't break even over it's lifetime.
By comparison solar panels break even is 6-8 years and after that they are expected to last 20 more years bringing you 2-3x installation costs in savings over their lifetime.
I can make some comparisons between the two too – ground-source maintains great COP even if its -20°C or less outside (as it was a couple days ago.) The incoming carrier liquid remains comfortably around 5°C, no matter the season. This also enables passive floor-based cooling. With an air-source heat-pump one would need some sort of a reversible cycle setup, I suspect, or perhaps a separate AC, which would likely bring the total cost of an air-source implementation up a little bit further.
It is also no-louder than your modern fridge. My neighbours’ air-source heat pumps’ exterior units were going at it so hard one could have been excused if they mistook there was a busy airport within an earshot. On the other hand if there's already an airport, what does it change if there’re N planes or N+1 planes in it :)
The main issue is managing humidity so that the dewpoint stays below the emitter temperature.
The downside of course is that its not going to make your already +40°C room into a flu-inducing +18°C one. Its more of a tool to offset a 2°C, maybe 4°C in extreme cases indoor temperature rise. Which is likely more than plenty for many airtight & insulated houses.
And indeed, managing humidity is hard. If this sounds at all interesting to the reader, definitely research whether this is applicable in your situation/area at all.
1) Heat pump - you use electricity to move heat from the outside in. It has efficiency over 100%, because you get all of the electricity's energy, plus some of the outside heat.
2) But generating electricity at the power plant uses heat in the first place, and wastes a lot of it. Let's bring the fuel to the house and make a heat-driven heat pump. This way you get 100% of the fuel's heat, plus heat from outside.
3) But this is still wasteful, because fuel burns hotter than the temperature you want in your house. So you could generate some electricity along the way, and use it to power domestic appliances. This way it will do useful work, and then 100% of it will also end up heating the house, because there's nowhere else for the energy to go.
4) And even that is still wasteful. The house is too hot in summer, and during the day, and too cold in winter, and during the night. A large enough heat reservoir, like thick walls, can smooth out this variation and give you average temperature all the time.
5) And believe it or not, even that is still wasteful. The human body produces enough heat to be warm in most temperatures, given good insulation. So we go from needing thick walls to needing thick clothes, which are much cheaper.
6) And even that is still wasteful! Because you don't need thick clothes either. So we arrive at the perfect solution for staying warm: a pill that makes your body heat up without fuss when it's cold, and lose weight along the way. Combine with clothes to taste.
Only part of this your body doesn't automatically do on its own is the "without fuss" bit. And that part can be trained.
A mitochondrial uncoupler like 2,4-Dinitrophenol will do this [1], but I don't think the risk of death is worth it.
1) heat pumps make much more sense when you don't burn things to power them. Solar PV, wind, hydro etc powering heat pumps mean you turn energy that is not heat into heat 2) there's no physical reason that you can't run a heat pump in reverse to provide cooling when necessary 3) I need to heat my house along with myself! In the UK there has been a "heat the person, not the home" movement in response to high heating gas prices. Result: a plague of damp and mouldy homes
A heat pump that is entirely powered by electricity generated from natural gas is most likely still more efficient than burning that gas to directly heat a house. Obviously though, using renewables is better.
ANY inefficient technology could get an efficiency boost just by using a heat pump.
But for this to happen HPs would have to be much much cheaper.
Just to make this clear: I was already comparing to a high efficiency furnace. I.e. a standard air-to-water heat pump (relatively common as a heat pump at least here in germany) would be more efficient at heating a house with electricity purely generated from natural gas than a natural gas furnace would be at its theoretical limit of 100%.
> This would have other benefits because you would not have to throw away an old furnace for no reason.
As long as there are no synthetic fuels for those furnaces (that can be made climate neutral) there is a very good reason to get rid of all of them: any burned fossil fuel is too much burned fossil fuel. We need to get down to zero.
It seems to me that scheme from my toplevel comment (point 2) was already more efficient than either of those. Namely, you burn the gas in the home, and use the temperature gradient to also run a heat pump vs the outside.
I am not exactly sure what that would look like, but I'd imagine it would at least be difficult to match the efficiency of a combined cycle power plant to generate electricity at home for the heat pump. Then again, as you say, you would have the "waste" heat locally to harness as well. Although this waste heat in power plants can be used for district heating as well, so it might also be used in that situation.
Anyway, my main point was that the sentence "heat pumps make much more sense when you don't burn things to power them." makes it sound like burning the same thing to heat your house directly was more efficient when in fact it is not, and potentially by a pretty wide margin.
https://cks.nice.org.uk/topics/carbon-monoxide-poisoning/bac... :
"It is estimated that there are approximately 4000 attendances at accident and emergency departments in England each year for treatment of carbon monoxide poisoning.
There are approximately 440 hospital admissions per year in England due to carbon monoxide poisoning.
Approximately 51% of these admissions are due to accidental exposure, and 40% are due to intentional self-harm (undetermined in the remaining 9%).
In England and Wales, approximately 40 deaths are reported each year due to carbon monoxide poisoning."
Neglecting clothes for a few minutes, your body both radiates heat and absorbs it. When you are in thermal equilibrium you feel warm. If your walls and roof had low grade radiant heaters on them and emitted enough infrared to balance your own outgoing radiation, you’d be warm, even if the air temperature was cold and you had no clothes on.
So if you covered your ceiling with cheap thin iron sheet metal and built small induction coils behind them and heated the ceiling instantly, you could instantly feel warm in a cool room. Exit the room and you turn everything off…letting it lose its tiny amount of heat.
So proper system design could let you have low latency zone heating. Since you usually don’t use all the rooms in your house at the same time, there ought to be more than 50% efficiency in that sort of a system.
2. Our current approach of heating the whole house through forced air is much less satisfying than having a concentrated heat source (like a fireplace) that you can just walk towards and get as much heat as you want out of. Maybe psychological factors might play in…if you “could” be warm with just a little bit of effort maybe you won’t mind being colder than normal. Maybe heat gradients are better for you than uniformly high heat.
Having lived in a place with ceiling heating, after the first couple of uses, I turned it off because it did nothing more than give me a headache.
> »A warm floor can induce high blood perfusion in the feet and consequently improve an occupant's health by treating many vascular-related disorders.«
https://pubmed.ncbi.nlm.nih.gov/19120501/
The article is from 2008, so there could be newer — or just other — articles out there coming to the opposite conclusion, but it does sound counter-intuitive that it should be bad for the blood flow. I'm willing to change my mind, though.
The tech industry once again coming back to amphetamines.
... probably the food needed to keep a constant body weight would be more expensive than paying for heating
ah, I see someone already posted it https://news.ycombinator.com/item?id=38925082
To add to this, the typical efficiency is 300% or more. Since typically most of the heat comes from being "transferred" from the outside.
Regarding 4 - https://www.granddesignsmagazine.com/grand-designs-houses/gr...
Different baseline electricity use and thermostat preferences could play a significant role as well. (Previous owners may have gone for a lower daytime setting and a deeper setback because of the inefficiency. A new owner with a more efficient system may quite reasonably choose to bias towards greater comfort than the prior owner did.)
I only got 2 quotes (and spoke with a third, but not quoted beyond ballpark). I ended up going with the local installer (which was the lowest, but I also worked with them on the furnace and liked them anyways).
It ended up being 20k CAD installed. If we're approved for all of our rebates (likely) we'll get 11k CAD back for a net of 9k which isn't too bad.
Our unit is supposed to be rated for 110% of heating capacity at -15c. We'll see , it's supposed to drop to -8c or so later this week :) We're looking forward to having cooling this summer (which we've never had)
It was mostly okay. It kept working even with the -20c windchill and was always putting out heat.
It's kind of subjective but I feel it struggled a bit eg the 'room' temperature shows a degree or two below the set temp. It never felt cold in the house (but a bit cooler?)
The sensor is probably in the control unit which IS in the hallway over the garage (and that side of the house always seems a bit cooler) so take that info with a grain of salt.
I am a happy air-source heat pump user, especially when coupled with solar panels. However there are other issues people need to take into account, especially if it is difficult to access the device for cleaning or the owner is mobility impaired.
However, at the small cottage I have for the first time just had the external units of two air-source pumps freeze solid due to snow blowing in in the current -16c spell. The defrost ran down inside the casing and formed a big block of ice in the bottom that has now reached up to the fan blades so the pump can't turn at all.
So I'm all out of heat pumps in the cottage just when I most need them :(
This is not enough to make me give up on heat pumps, but it makes me wary to rely solely on them.
Am planning a big new build, and will of course go air source to underfloor heating, but am seriously considering a backup combo wood burner for the panic week that comes each year.
The issue is that the defrost mode will defrost all the ice from the fins, but it freezes again before it can all drain through the small drain hole on the bottom of the housing. It's somewhat a known issue with air source heat pumps, sadly. I've not run into this issue myself, but on a Dutch speaking forum (tweakers) there is a long thread about this modification to "survive" the cold spells with this small modification.
You can manually attack the ice with a heating gun or hair dryer to remove it, but that's a faffy.
I think manufacturers should, and probably will, add something like this themselves in the future.
Anyone on forums advocating for drilling bigger or more drainage holes?
Though, if it's snow blowing directly inside then I think creating some barrier or add additional shielding of the outdoor unit is required,so that you minimize the chance of the snow DDoS-ing the unit (note: check your unit's service manual for the minimum free distances from all sides of the unit, especially the front one that is the most important to be kept enough free space).
Also, I've been wondering how much efficiency would I get if I could put some mirror and direct the light to the unit in the winter. It could help with defrosting as well.
*I was considering horizontal heat pump, but it's not worth it. It affects vegetation and future construction.
Of course it all depends on options government offers and in what place you live - however Poland I suspect also gets snowy. Just sell excess solar electricity and re-buy in winter. Just trying to save you some money on batteries.
What if you live on the Xth floor? Your gas burner is small enough to be all inside and easily serviceable when it breaks in the middle of winter (why would it even consider breaking in summer?). Where do you put the much larger heat pump and how do you reach it?
And the only answer is that it completely depends.
We spent €30k renovating our house but that included removing the entire old heating system, installing underfloor heating, extra insulation, ventilation, remove of gas pipes, new electrical switchboard, upgrade to 400V electricity and, well, the heat pump.
Just the device itself (air-water) is probably €6 or €7k excluding a €3.3k subsidy.
Isn't it worth putting a turbine in there to recoup the energy released as a high pressure liquid passes through a small hole?
Even if it's only 10%, that's still 10% of the energy use of your home for a decade - surely that pays for a micro turbine (which need not be particularly complex - the same design used in those $3 light up novelty faucets would probably work.).
reduce the heating temperature by increasing the area you're radiating from - floor heating / ceiling heating is way more efficient than radiators since you can deliver the same amount of heat at much lower temperatures to the space.
Negative: Not a fan of the weird noise the unit outside my bedroom window makes at a more consistent rate through the winter and it annoys my neighbor too.
Overall got the home warranty to cover about 10k of the 16k replacement, after learning about going to arbitration here on HN!
Definitely happy with the conversion overall thus far. Jury is still out on long term reliability
This is a pretty useful guide for me since I've wanted to look into getting a heat pump for my home. But it doesn't get into the first stumbling block that much: _finding_ a contractor! It mentions contractors some, but doesn't talk about those that do heat pumps vs those that don't. Around where I live in Northern Indiana, I haven't really found anyone that's got a ton of experience installing, working with, and (importantly!) repairing, heat pumps.
> A dual-fuel heat pump works in conjunction with a furnace. During the summer months, the heat pump works like a high-efficiency central air conditioner. In mild spring and fall weather, it provides cost- effective and efficient heat. As the temperatures drop in the winter months, the pump shuts off and lets your furnace take over.
* https://www.lennox.com/buyers-guide/guide-to-hvac/glossary/d...
* https://www.trane.com/residential/en/resources/glossary/dual...
More of a thing when heat pumps were more expensive and/or not as capable as they are now: going down to only 5C or -10C, whereas now units can go down to -25C.
They could also still be useful in places with less reliable power (rural? coasts?), as a heat pump need more electricity, whereas a furnace just needs to power a fan and an ignition system, so a small portable generator can handle the load (or it won't tax your battery system as much).
Only a handful of centrally ducted heat pumps on the NEEP list (https://ashp.neep.org/#!/product_list/) have COP >4 at 5F outdoor temperatures.
https://www.blueheartenergy.com/ https://www.equium.fr/en/home
Especially considering buildings have less wall/roof area to lose heat from on a dwelling by dwelling basis, even a small-ish building with gas heating with average insulation would still be much cheaper to heat than a house by square meter.
About 81 million detached single-family vs about 30 million multi-unit housing. https://www.statista.com/statistics/1042111/single-family-vs...
The more you know about your own system, the more you can save. Even if you don't intend to do any work yourself.
- Get a few quotes and iterate on the plan. Save the contractor you'd most prefer to work with for last, because you'll have a much better idea of what you want by then, and your knowledge will save you money.
- There's a fun puzzle to retrofitting older homes (no existing ducts): where you place the lines, where you place the units, and where you place the heads are all variables to play around with. This is part of the reason for getting different quotes. Only the last two contractors I spoke with were able to come up with ways to keep all the external lines on the side of my house and away from the street. Only the very last contractor offered a ducted system for bedrooms, so I have head units downstairs but the upstairs is vented.
- No one will run a real Man J calculation, they all use proxy calculations. This should be fine but you almost certainly want to slightly undersize your system. If your system is always turning on and then turning off (because it is oversized and heating / cooling the room very quickly) you'll end up with humidity and mildew problems, you want it to be running "low and slow" while it's on.
- They work amazing for air conditioning. For heat, your existing boiler + radiators is often nicer and more cozy. It's also often cheaper — heat pumps are electrically efficient, but natural gas costs vary significantly by location and for me (~Philadelphia) heating with my boiler is a lot cheaper than doing it with the heat pumps.
- I live in an older home, so before I installed heat pumps I had to replace my ancient windows for modern ones that didn't constantly leak energy. I'm happy with the results but it adds a lot to the startup cost.
I intentionally had a contractor install a unit that was undersized per Manual J in a room, and, as tested during a nearly-record-breaking heat wave, it kept up without coming close to its limits.
Fortunately, a lot of modern systems have respectable turndown ratios (better than 5:1 is not that hard to find), so as long as you use controls that can operate the system all the way down to minimum power, oversizing is not that bad.
Panels are pretty big and located in the ceilings and walls so should help aswell.
(The labor issue: 300,000 HVAC professionals in the USA but just 145,000 companies).
In fact, the business is initiated just two days of the year! The first hot day of summer and the first cold day of winter. When somebody's old system breaks and they find out exactly when they need it most!
So it's always an emergency, and always when it's very unpleasant to work outdoor.
Seems clear why nobody is going into the business. One of those 'dirty jobs'.
Maybe a business model that spread things out? Like, a contract to support heating and cooling year-round, schedules upgrades, does periodic testing to anticipate breakdown.
I imagine now it's more like folks that have snow-plow trucks, promise to plow out your parking lot after each big snow. They work just a couple days a year in Iowa, and have regular jobs the rest of the year. The companies are less than half a dozen trucks typically, with a huge demographic spike at 'one guy, one truck'
The temperature of a natural gas flame is 2770C. Using it to heat a house to 30C is ridiculous. Instead you should run a gas turbine off of it to produce electricity. The exhaust should run a steam turbine which makes more electricity. Then a heat pump can capture more energy from the exhaust (and from your bath water etc) to pump more heat into your house. The electricity can be used to charge an electric car or run a gpu inside your house (and produce even more heat).
Heat pumps should be utilitarian and 10x cheaper, and used in multiple places. They should not be something you “invest” in with a 10 year payback time.
Why?
the carnot limit for 30°/0° is 1 - 273/303 = 9.9%
so if your gas flame is really 2770° (which i doubt, the adiabatic flame temperature for methane in air is only 1963° and actual flames are even colder than that) you're wasting 90% of your exergy by diluting it down to 30°
also tho i do not want to go to your house if you heat it to 30°
specifically, in this case, if you convert a hypothetical 2770° flame into mechanical work in a hypothetical heat engine capable of withstanding it, you can use that mechanical work to drive a heat pump to pump ten times as much heat into the house to heat it up to 30°. or more, if the temperature outside is higher than 0°
A carnot heat engine with a hot side of 2000C(Th=2273K) and a cold side of 200C(Tc=473K), has an efficiency of 1-Tc/Th or 79%.
So you can do useful work (hopefully inside the house, where it too will eventually end up as waste heat) AND recover energy from the exhaust gas of the carnot engine--which is 200C!
Imagine burning natural gas in your furnace, vs using your natural gas to run a electricity generator and mining bitcoin with it inside your bedroom. A Bitcoin rig makes a great space heater.
Additionally, heat pumps can already be purchased cheaply from the hardware store. These are closed systems with the refrigerant already inside. However, if you want a larger central air system then that costs a lot more because you need to hire licensed HVAC professionals to handle the construction and charging of the refrigerant loop.
Locally it's not worth DIYing a heat pump install. The tax incentives and rebates easily cover the cost to hire a licensed and insured HVAC company to do the entire install for you, plus then you get to choose from a much wider selection of heat pump models which likely enable buying something better sized for your need and more efficient.
Anyway, is more efficient to use gas for generating energy and using that energy to heat places with heat pumps than burning gas on furnaces. If you can use the residual heat of the energy generation is even better.
I'd add a few things:
- Heat pumps have been around a while. In the southern US, there are lot of older HVAC techs with a negative perception of HPs based on problems with older technology. Older HPs had less of an ambient operating temperature range, in which case the emergency heat would activate, reducing savings.
- Re: fragmented markets, different states/cities/towns/municipalities have different rules, processes, procedures, etc.
- Re: the desire for drop-in installations, the construction permitting and inspection process is a big fat roadblock which is linked to the problem above.
Like most machinery, if it's mounted to your wooden or steel framed house, it's going to vibrate the shit out of it most likely. I have mine on a concrete slab.
Ours seems to be about 45 decibels.
It emitted around 69 dB (measured on our side of the property, also checked by an expert). Allowed (on the border of the property) were 35 dB (rule of thumb: you should not hear it in the surrounding soundscape; note that this is a logarithmic scale so I think it's a factor of 6 or something)
It was especially bad when it had less than 8 degree Celsius because it would defrost every 30 minutes or so.
As I wrote before: location is also an important part: his house is hard walled, ours is a prefab house built out of wood. There are only 4 Meters between our houses, it was approx. 2 meters from our wall blowing in our direction. They only thing they could have made worse is putting it in a corner.
I didn't only hear it, I felt it.
In the end I managed to convince him that I pay an acoustic expert to explain to him that 65 dB is way louder than 35 dB and that putting an acoustic hood around it does not solve the problem (approx -10 db).
As far as I can tell there are no efficient heatpumps available on the market that can sit legally less than 6 feet from the property line in Seattle and supply a 5 ton system
[1] https://www.energy.gov/energysaver/geothermal-heat-pumps
For bigger setups it would make more sense to capture the heat locally and distribute them to a whole neighborhood given how much deeper it would need to go.
It seems ground-sourced is a much better idea than air-sourced, and it seems to me you could install the ground loop with/under/around the foundations for new builds.
As far as indoor distribution goes, it seems like a low-temperature hydronic system would be most efficient, and most comfortable. Or at least a hydronic (instead of refrigerant) loop to multiple chiller/heater units, which would be easier to install and change.
You're right that ground-sourced should have better efficiency and thus running costs, especially in winter.
The gotchas are the energy used to run the circulator for the ground loop, and the fact that over the course of a heating or cooling season the ground temperature lowers or raises, respectively, by enough that the COP isn't even much greater than an air-source system (but this would definitely vary by climate).
Coupled with the much higher installation cost, it's a bit hard to make a system pencil out for a building the size of a single-family house.
Generally it is extra logic so that you have a "Heat_1" source (HP) and a "Heat_2" source (switch to burning).
The inside unit (furnace, air handler) and outside (AC, HP) unit need to have some level of compatibility. Check the sticker on your furnace to find the model number and see its capabilities.
I like my hvac company so didn’t push too hard but wondered if this was true or just their inexperience.
That said, if it's rare to run your heating then a standard AC unit is probably marginally more efficient than a heat pump for just the cooling operation
So far most heat pumps are a step up in price in the US compared to the traditional furnance/Ac setup. If you only needed the furnace replaced it might make sense to only replace that and not spending the extra multiple to replace the entire system.
HVAC companies don't like heat pumps because they cost more (mostly for no good reason - but you may need a larger heat pump and air conditioner), don't put out as warm of air as a gas furnace, and are slow to change temperatures (don't not get a setback thermostat with a heat pump!). Customers do not understand them and end up unhappy and complain about them. However if you get one anyway understanding the limits you will save a lot of money.
Use the cold side to dehumidify the air, then pass it over the warm side to heat it up.
Net-net, no extra heat in the room it's operating in (beyond the motor and such), and a nice self-contained unit that doesn't need external venting.
This is still a win because it doesn't depressurize the house (any air you vent out of the house is eventually replaced by outside air, sometimes via dirty areas like crawlspaces and attics). But the heat pump ones can run off of a low-power (~1500W) circuit whereas the condensing ones typically need a higher power (~5kW) circuit.
But it still blows my mind every time — that we can use the heat of the sun to cool our homes. What a wonderful time to live in!
> Heat pumps are unique in that they are a tool for fighting climate change, where we have the technology today.
No. They are not unique at all. We have electric cars, wind turbines, solar panels, hydroelectric, nuclear, recovery of methane from waste, "smart grid" technology and many many other things today. And not just "the technology", in some theoretical sense, we have all of the above actually working now.
There's also things like more efficient light bulbs and electronics that use less power when not in use that are now nearly 100% of the market. You can't buy incandescent light bulbs or TVs that use several watts of power in standby mode any more.
In my opinion they still are pretty unique because their efficiency is higher than 100%. Which was what I thought the sentence would continue with when I started reading it. Cannot be stressed enough. It's like magic :] Sure your LED is more efficient than your incandescent light bulb, but it still produces heat which is not intended nor really wanted. In my book there's no comparing that to a heat pump. That being said, not really a fan of such sentences either.
If you measure the efficiency of solar water heating in the same way, it uses no electricity, so it's efficiency is infinite.
So it's unusual ("unique" is a high bar) in that it's one of the largest privately-owned energy-consuming devices where existing technology can result in substantial energy savings and emission reductions.
Yes, because for every unit of energy you directly put into it (in the form of electricity) it outputs more energy (in the form of heat). Which is unlike any other typical heating system, which usually puts out less or at max the same amount.
Highly efficient natural gas setups remain much better for many settings.
So it is an improvement even if the net is 100% dirty. But it isn't, even in winter we can get a lot of electricity from renewable sources.
I think there are two big issues with heat pumps: they are expensive and require well insulated homes. Both problems can be solved.
In general I think natural gas prices will continue to go up as people switch to electricity or more efficient gas setups. Less gas usage means additional fees for infrastructure. As prices go up, more people will switch. It's a feedback loop. At some point it won't be worth it to run the infrastructure for natural gas anymore.
1. Noise levels (inside)
* Fundamentally, a heat pump runs more often than a furnace. So, air is semi-constantly blowing out of your vents, rather than a few bursts throughout the day. Also, the air is tepid, rather than warm. Previously, there was a "yay, the furnace is on" moment of enjoying the warm air. Now, it's more of a "jeez when will this thing shut up again?" throughout the day. It reduces my quality of life.
* One of our vents points at my back where I sit to work. With the furnace, that was enjoyable. With the heat pump, it's a nuisance. I taped over the part that blows on me. Similarly, we have a vent in the bedroom that we mostly keep covered with a pillow these days, due to the noise.
* In documentation, noise is often measured in decibels — indicating max loudness. And by that measurement, the heat pump is no worse than the furnace (maybe even a bit quieter). But the fact that it's on near-continuously at that noise level is what causes my annoyance. So, it's not just loudness, but also how continuous it is.
* We had existing ductwork, so the heat pump's air handler uses that (just like the old furnace). This is a common situation, but what nobody mentioned, across multiple estimators, is that it's likely the old ductwork will be "under-sized" relative to the new system. This means higher static pressure, and importantly, more noise at the output vents. Talking to the technicians, this is a bit of a crapshoot — you might get lucky with noise levels, or might not (like me).
* Loudness will also vary depending on how far from the central unit you are (my house is fairly small), how many vents there are, and various other factors.
* In theory, you can determine if the above will be a problem by doing measurements beforehand. None of the estimators mentioned this; they just want to sell you the system, of course. I didn't realize until too late that you can probably find someone, pay them a few hundred dollars, and get this information upfront. There's a whole science to it, with specialized tools. Look up "Manual J, S, D, T measurements," for a starter.
* However, even if you get that info, it still depends on your sensitivity to these things. For instance, my wife is much less bothered by the noise than I am.
2. Thermostats
We got a fairly modern "communicating" system. This means the outdoor and indoor units talk to each other, allowing better efficiency.
This sounds nice, but what it means is that you will be locked in to your vendor's choice of thermostats, since the communication protocol is proprietary. These are generally more expensive than the alternatives, and you won't have many options — perhaps only one.
If you get a "non-communicating" system, you will be able to try various different thermostats — eg: a simple one from your hardware store, or a Nest one, etc.
3. Other
* The old oil furnace was a simple machine, with a lifetime warranty on the heat exchanger (basically a hunk of cast iron) and can basically last forever with decent maintenance. The new heat pump has a 12 year warranty, and the system might last 25 years with good maintenance. The HVAC estimator seemed proud of this, but to me it doesn't seem like an especially long time.
* If you use old ductwork like mine, it may not be insulated to modern standards. This is both a noise issue and potentially a condensation issue when the AC mode is running.
* It's very difficult to know when the "emergency heat" mode is being used — where resistive electrical strips are used to generate extra heat, if the heat pump isn't producing enough. This mode is much more expensive than the heat pump alone. It boggles my mind that such simple (and useful) information is so hard to obtain.
* If you want to get government subsidies, do your research about what exact make/model is covered by it. Ironically, sometimes the more modern and efficient systems are not subsidized, presumably because there is some lag to update policies.
* Generally, remember that the estimator who might come to your house is a salesman, first and foremost (:
4. Pros
Okay it's not all bad; some positives include:
* AC in the summer. Probably the biggest positive.
* No dependence on oil — both for cost and environmental concerns and risk of tank leakage (ours was aboveground, so less of a worry)
* No carbon monoxide worry, since there's no combustion going on.
But overall, I'm not sure it was worth it for my case.
There are rules of thumb for duct work that are pretty easy to use to estimate. A 6" round duct, for example, is designed for about 80 CFM (not counting any restrictions on the register/grille.) That 3 ton system is going to need 15 'takeoffs' of 6" duct to handle that air. Adding more duct work can be expensive if the majority of it isn't in unfinished locations like a basement or attic.
In Europe air conditioners come with heat-pumping functions since ages ago.. all installed aircons can heat or cool. But I personally found such heating ineffective and lame.
What's going on?
Because of their efficiency. They are typically 200-400% as efficient as electric resistance heaters, because the energy is used to move the heat from outside.
>I personally found such heating ineffective and lame.
If it's a proper heat pump, the heating won't be ineffective or lame. It should pump out air > 30C, and is sufficient to keep your house at 21C even when outdoor temp is 0C.