Air Source Heat Pumps. Real world experiences?

Have you had an air source heat pump system installed in the past few years? I would be interested to hear how you have got on – the good and the bad.

The reason for asking? I have got some quotes, more or less lined up to press ‘go’.

Lot’s of folk I speak to say ‘ooooh, you don’t want to do that….they don’t work etc etc etc’ but then they admit they don’t actually have a heat pump (or actually know anything meaningful about them)!!

I only know a couple of folk who do have a system installed – who have been very positive about it.

Therefore am just keen to hear from a few others with actual experience. Ta.

I had an ASHP installed 3 years ago and love it.

They work is the short answer and our energy use is significantly lower than with previous gas central heating and CO2 emissions lower still.

I live near Edinburgh, happy for you to call round if you are local or have a chat.

We have had an air source heat pump for the past 2 years.
Before installing it we had old electric heaters so anything would be an upgrade. The air source has been pretty good but we have found that adding insulation to both under floor and in the loft has made a massive difference.

Recent install (less than a year)  but so far so good.

Never hear it, plenty of heat and hot water. We replaced ground floor in kitchen/diner so it’s insulated to the nines and wet underfloor heating. Walls and roof insulated. rest of house is still on ‘normal’ rads.  We did have to swap out one radiator to a bigger size but that rooms was cold before on an old gas boiler.
we did replace mains water from meter to house and get better pressure (with pressure vessels) so no need for showerpump (runs two showers for adult and teenage girls at some time).  Needed a  bigger water tank.

cost wise electric only is probably cheaper than old gas boiler and range (we’ve binned gas completely). Run constantly to dry a big concrete slab so first few months were more expensive than planned!    Can’t be arsed at present to fill house with tech to make it as efficient as possible

Downside is you don’t get hot rads to lean on/dry wet cycling shoes fast and it takes a change of mindset to have it run ‘all the time’  against two short bursts of heat morning and evening.

Later if we add solar electric panels, will seems cheaper

Have a Nibe ASHP installed in my 3 year-old 110m2 house on the Isle of Mull, my electricity bill is fixed at £134/month – I have a wet UFH across the ground floor and radiators upstairs. We don’t have gas or any other form of heating. I adjust the temperature curve on my controller in autumn and spring – that’s it, it just works.

Energy tariffs now make running one even better.
Ovo have partnered with Vaillant and Viessman and only charge 15p/kwhr for heat pump use…..

other companies have tariffs which help too I’m just not up to date on those.

Had one installed about a month ago (plus PV and a battery) so not used for heating yet, just hot water, which is fine. The unit itself is very quiet, can’t hear it inside, and it’s fixed to the wall. We had most of the rads replaced to compensate for the lower flow temp.

We used to be on oil (no gas here) and both the tank and boiler were getting close to needing to be replaced, so we went ASHP to save that cost, plus the grant from the Govt helped.

If you are getting one, please make sure the designer and installers know what they are doing. The flow temperature should be 40 degrees maximum, but preferably 35 degrees. Make sure they do a proper heat loss survey, so that the radiators are sized correctly.
I dont install them now (actually, I’m fitting one in my own house in the next few months), but I do a lot of fault finding. Flow temperature, and cold rooms are the main causes of complaints. The higher flow temperature causes high electric bills, and the small rads, mean the room never gets warm. Both can happen at the same time.
Each degree rise in flow temperature equals around a 2.5% increase in electric use, so running at 45 degrees will cost 25% more than running it at 35 degrees.
Many of the after fit market are specifying the HP to run at 45 or 50 degrees, press them on that, and dont take no for an answer, they may gove some rubbish about weather compensation (which should be used), but find out what they have designed it as, if its above 40, tell them to do it again for a 35 deg. flow, if they say they cant, go elsewhere, as they clearly dont know what they are doing.

I would add that 50 deg flow is only when outside is minus 3 so a fully modulating weather compensated heat pump should still work with higher temps, providing it uses R290 as a refrigerant.
But the lower the flow the cheaper it will be to run.
I’m getting COP of over 6 heating my hot water to 55, flow is set to be maximum 60.
obviously it is summer so plenty of warm air.

though one heating period is overnight utilising cheap electricity.

Design is key though.

Many thanks for all the information above. I know the forum wouldn’t let me down 🙂

It is quite a steep learning curve – so your comments are much appreciated. Cheers.

Many of the after fit market are specifying the HP to run at 45 or 50 degrees, press them on that, and dont take no for an answer, they may gove some rubbish about weather compensation (which should be used), but find out what they have designed it as, if its above 40, tell them to do it again for a 35 deg. flow, if they say they cant, go elsewhere, as they clearly dont know what they are doing.

Bugger. Wish I’d known this earlier.  We had an ASHP fitted by Octopus a month ago, amd the flow temp is specified as 50. Was kind of assuming as a pretty big supplier who seem to be well regarded in the energy market, they’d know what they were doing. They did replace a LOT of radiators though and they new ones are a lot bigger – in one case literally three times the size. The heating is set to 19 deg and it’s kicked in just one morning so far, on Monday this week, but the hot water has been great – way better than the gas combi it replaced.

Had one fitted about 3 months ago so not gone through a winter yet. We have solar and a home battery so this time of year the ASHP is only providing hot water. We have a 250ltr tank. We are off gas now so only have an electricity bill which is negative to the tune of about £15 per month as we are still feeding in more than we use. (4 bed detached, 3 adults at home)

Winter will of course be very different but our house is well insulated and our gas boiler was >50yrs old when we took it out so I know very inefficient. I didnt do it to save money I did it to reduce our carbon footprint so if we come in cost neutral then I will be happy.

I’ve been running ASHP in an old Georgian house for nearly a year now. At the time of designing it, it was really striking how few people actually *know* ASHP properly – we had architects basically sucking their teeth and saying it wouldn’t work because the house isn’t insulated enough and is too damp; other architects saying of course it’ll work it’s ASHP and therefore a magic bullet; various folks saying it needs to run the whole time otherwise it’s pointless, and so on.

Not sure what to report, but I got a mechanical engineer to run the numbers on U-values, volume, hot water needs to come up with the size of heating system we’d need, and we got a heatpump to fit that.

It took a couple of weeks for the house to warm through when we first turned it on; and the bills the first few months were a bit eye opening (€600/ month every month), but it’s warm, pretty consistent and actually not that expensive to run overall

Have a Nibe ASHP installed in my 3 year-old 110m2 house on the Isle of Mull, my electricity bill is fixed at £134/month – I have a wet UFH across the ground floor and radiators upstairs. We don’t have gas or any other form of heating. I adjust the temperature curve on my controller in autumn and spring – that’s it, it just works.

I’ve just had a Nibe F2050 ASHP installed along with a VVM S320 indoor unit. Seems to be doing fine with our hot water requirements so far, no heating demand yet. Would you mind sharing your heating settings please? So I can compare with what mine’s been set up with.

My neighbour has one and the noise is intrusive.

Some of my neighbours have them and the noise is, well, nonexistent.

My mate has one under the balcony supplying all his heating needs and it’s a bit noisy for ~15 seconds when the fan kicks in, but then settles down to a quiet hum. Probably quieter than the gas CH i had in the UK. And quieter than the start up and shut down noise of my GSHP if i leave the service room door open.

Costs him less than the wood/pellet/electric he was using before. A lot less. Now he’s got solar/battery as well the electricity co is paying him due to local feed in tarrifs.

My ex-inlaws have one (just for heating, no hot water), the outdoor unit is ~1m from their bedroom window. ex-FiL would have ripped it off the wall and hoofed it into the next country if it’d had been disturbing his sleep. They’ve also now installed GSHP, so the ASHP is now used as a booster and AC (it’s a dual directional one).

our energy use is significantly lower than with previous gas central heating

This can only be down to insulation, not the ashp itself

Ours is 8kW and just outside the kitchen window. I can barely hear it even when the window, 12 inches away from it, is open. I think the newer the unit the quieter.

Got one, brilliant especially with solar panels. The whole house basically runs itself for free. Nobody has mentioned, but it’s worth knowing depending where you live, ours can be run in cooling mode. So the floors become cool and it’s like a low level air conditioning.

ours can be run in cooling mode

Thats interesting. Ours has a “slider” on the app that allows it to “cool” We dont have UFH only radiators. Does that mean it will cool the radiators i.e cool and pump the water in them, and if so I wonder if that would have a noticeable effect on room and house temperature…. Not bothered either way but curious.

This can only be down to insulation, not the ashp itself

that’s not true. an ashp will be more energy efficient (~3x) than a non-heat-pumped-heating-solution, be it gas or electricity. It runs on expensive electricity though, so it may not be cost effective.

Thats interesting. Ours has a “slider” on the app that allows it to “cool” We dont have UFH only radiators. Does that mean it will cool the radiators i.e cool and pump the water in them, and if so I wonder if that would have a noticeable effect on room and house temperature

There are two types. Split units allow full cooling internally, for this they have fan units in the radiators, or soem other form of getting the cold water to the emitters.(split units have the external box as normal, but also an internal box with all the heat exchanger kit in it, usual ASHPs have it all in the external box)
Normal ASHPs can use the radiators and UFH to cool the room, though it will only be suitable to around 17 degrees, as below that will cause the floor/radiators to be at the dew point where the water in the air condenses, and covers the cool object. Not all ASHPs can do it, but many can, some with a small tweak of the settings, others, like the Vallaint, need a cheap chip inserted to allow cooling in the settings.

Cant say about the radiators. Our floors are noticeably cool. We run it about 20degC and it keeps the house nice and cool on the hot days without getting condensation. We had it cooler before but got a slight big of condensation which makes the floors slippery.

About 3 months with a propane (R290) based heat pump plus solar and batteries. We picked propane for better CoP at low ambient temperatures vs R32. Paid a little bit more than a R32 unit. No radiators replaced, but we did have to change our water tank for a 300 litre unit to make sure that they warrantied the whole system (have a 250litre perfectly fine water tank if you want it ?).

Early 2000s timber frame house. We’re basically breaking even during the summer, including running an EV.

Plenty of hot water, and not anticipating any major issues during winter. 10kW unit for a 190m2 house.

Don’t underestimate how noisy they can be, don’t situate one near a bedroom or neighbours house if possible, you can get acoustic enclosures but they’re rather spendy. Apparently local authorities are doing away with gas boilers for schools in some areas. They’re the future, or so I’m told.

10 years here in what was a new build with under floor heating, no radiators. We’re usually running between 23/24c during the summer months (ambient temperatures mid to high 30’s)

  To be more then frank, our neighbour’s aircon is way louder. Yes, you have two fans on the outside of the building, but if designed and installed correctly, the noise will not be intrusive.

The best feeling ever is walking around the house barefoot on the coldest morning or the hottest day!

I would emphasise the comments above about finding an installer who knows what they are doing.ASHPs are different to gas CH and not as well known .

An installer should measure up the house, check your requirements then go away to run the sizing calculations.

I am sure that many of the heat pumps don’t work stories are down to poor specification. This can be so with any technology, especially when not well known.

As pointed out above, ASHPs consume about one third the Kwh of gas for the same heat output but electricity is more expensive per unit.

I wouldn’t cool with radiators, they will run with condensation.

you can passively cool via UFH or actively cool using a fan coil such as Jaga or Innova.

Can anyone recommend a good source of info. on heat pumps and sizing?  I’m interested in going down this route but because you can’t always rely on the installers to make the correct decisions I would like to be informed before we start

Leffeboy chose your installer carefully they will do all of that for you.
Unless you can understand heat loss calculations, know about air change rates, building fabric design, pressure loss calculations, then there are so many variables.

Our installer measured each room and the existing rads, and estimated the heat loss from walls, ceilings and windows, based on the age of the house. Then proposed which rads needed replacing based on the lower flow temps. We ended up replacing 10 out of 12 rads. Kitchen has UFH so left as it is. One of the rads was replaced because we didn’t think the old one was enough, based on last winter with the old oil based system.

Very pleased with our installer, who just do heat pumps and solar, but only used for hot water so far (Eco Installer and Service, just outside Ely, Cambs). As to noise, if you’re outside you need to be within about 2 metres to hear it. Inside nothing.

My neighbour has one and the noise is intrusive.

Can’t be worse than five oil boilers firing up simultaneously at 6am.

Noisy ASHP outside units are usually down to bearing failure following a bad installation (they need to be absolutely level).

Leffeboy chose your installer carefully they will do all of that for you.

I’d still like to understand what to listen for, I don’t want to do the calculations myself though.   Having had a bluffer at work who got through the interview by wowing the people doing the interview but couldn’t actually do the work I would like to be able to spot when then aren’t aware of what they are doing e.g. to 50deg thing above (which is probably the one bit of info that I knew)

Alternatively, a list of things to look for in a supplier would be interesting, e.g. would you expect them to do a full energy audit on your house to estimate losses first?

Our installer charged us for the survey, which was refunded when we placed the order. They need to do it first so the quote can include thinks like replacing rads.

@alanl

Many of the after fit market are specifying the HP to run at 45 or 50 degrees, press them on that, and dont take no for an answer, they may gove some rubbish about weather compensation (which should be used), but find out what they have designed it as, if its above 40, tell them to do it again for a 35 deg.

When you say ‘specified at’, what does that means if they’re using weather compensation as the flow temp will be variable?  Whats the external temp for that flow?

Cooling – this guy was messing with it in the UK and wasn’t impressed. Cold feet, condensation, negligible cooling effect.  Would be interested to hear more but suspect you’re never going to get much because the delta between a floor above dew point/comfortable to walk on and room temp isn’t going to be very great. https://x.com/plumbers_urban/status/1814358476476522595

Also IIRC – most UK systems don’t cool as that means they become ineligible for subsidy/grants etc?  (that’s why air-air dont qualify)

[Weather compensation varies flow temperature based on external temperature to use the lowest (most efficient) flow temp to maintain internal target temp.  Should be using it even on gas boiler systems as maximises boiler condensing mode and gives more stable internal temps.  Needs use of long heating periods – ie not UK typical ‘blast for a few hours when get home’ approach.]

If you really want air conditioning and heating, look at air to air heat pumps, which duct air around the house, ether heated or cooled. But you need ducting around the house. Rads are designed to heat, not so good trying to cool.

Have a look at Tim & Kat’s Green Walk on YouTube.

Heat Geek train ASHP installers and will guarantee their work (to a specific efficiency).

https://www.heatgeek.com/find-a-heat-geek/

A useful resource in simple language.

https://www.lowcarbonlifestyle.online/_files/ugd/284f0d_f64a98daf1894b4e81f2524cd8339852.pdf

A good way to test if your house is suitable (with current radiators and insulation) is to turn down your flow temperature on your boiler to 50 degrees or ideally lower. You will have to have your heating on for longer to achieve a comfortable temperature.

If you can get comfortable at 45 degree flow temperature with your heating set on all day then you should be able to do a straight swap.

This approach will also save gas if using a combi boiler.

How to reduce your flow temperature video.

https://www.youtube.com/watch?v=XQk8ZVLIsOc

@leffeboy where are you in the country? Search if you have a carbon co op group near you they are usually free / cheap to join and produce lots of resources.

Also Scotland residents have access to fantastic grant and interest free loans via https://www.homeenergyscotland.org/

Glasgow https://locohome.coop/

Manchester https://carbon.coop/

Cambridge https://cambridgecarbonfootprint.org/

Find a group https://www.lowcarbonhub.org/community-members/community-groups/

I’m not an installer or have an ASHP (yet) but I have an interest. Hope that helps.

When you say ‘specified at’, what does that means if they’re using weather compensation as the flow temp will be variable? Whats the external temp for that flow?

It means it has been designed for a 50 degree flow temperature. If its set for weather comp, it may reduce the flow temp a bit, but, if designed for 50 deg flow, the radiators will not be giving enough heat out. The rads are sized according to the flow and return temperature, and the required room temperature. If a design says 50 flow, 40 return, with 20 room, then it is a DT of 25, so the radiator has to be spec’d for a DT of 25. (typical rads are quoted at a DT of 50, so for 25, you’d need, roughly, double the size – there is a calculation, it isnt quite double).
Now, if you had a flow of 35, and return of 30, the DT would be 12.5, so the radiator size (or any heat emitter) would need to double in size again. Of course, this is all at the minimum outside temperature when those figures are needed, but it shows that the design should be done properly, with a low flow temperature from the outset to reduce ongoing electric costs.
So, yes, WC will reduce the flow temperature when required, but it will run at 50 degrees if it is cold outside (below 5 degrees I’d guess at), and then reduce as outside temperatures increase.

Heat Geek train ASHP installers and will guarantee their work (to a specific efficiency).
https://www.heatgeek.com/find-a-heat-geek/

Although undoubtedly they have a good reputation, be aware that anyone on the map (it has been down for the last week) have paid to be on it. £350 a month to subscribe to it. I used to be on it, but it makes no commercial sense for me to pay them £350 a month when they dont even operate in Scotland yet. There are many others in the same position as me, there are around 900 people who have qualified by doing the HG courses, yet less than 100 on the current online list, whereas they all used to be on the map, rated in different sectors, such as HG Qualified, HG Assured and HG Elite, HG Qualified didnt have to pay anything, just pass the courses, the other 2 paid varying amounts to be listed. There are some checks on the Installers, so picking one of the HG Elite should give a good installation.

What I want to know is – how do I get it for free with the £7,500 grant?

You will struggle to fit radiators sized on delta T of 12.5 unless upgrading insulation.

Also your flow and return temps are wrong you want to be looking for about a 6 deg differential between them. You can open it up if you use a buffer.

I wouldn’t be worried by a design using 50 deg flow, providing rads and pipework is correct then the system will be fine and should achieve the magic SCOP of about 3.

Designing with 45 flow and 40 return would obviously be better and is often achievable even in retro fit installation.

A heat pump connected to fan coils will work very well at cooling, some you need to add controls to, others come ready to go. Pipework will need to be insulated in Armaflex type insulation entirely otherwise condensation will be an issue.

we are working on a lot more systems where cooling is being used. For those that have access look at the CIBSE article on the heat pumps in a container on a construction site in Wembley.