Air source heat pumps

I had a dude round yesterday looking at the suitability of my house for an ASHP. Naturally the answer is “it’s complicated” rather than yes…

The primary issue is noise. There is a requirement for a maximum of 42 dB at a neighbour’s door or window, and that’s tricky in my small garden. The ideal place for a heat pump for me would be pointing right at a neighbour’s bedroom window. It’s likely that the only permissable place would be right underneath my bedroom window.

Has anyone actually got one of these? How is the noise? If I can’t put it within 4m of a neighbour’s bedroom I’m deeply sceptical of putting it right next to my own.

Are you sure it is 42db max …

The answer is to turn your climbing wall into an enormous heat exchanger with a massive fan that can run at low rpm.


I’m not sure of anything really, nobody publishes dB levels of the ASHPs as it’s complicated, apparently.

I had EDF quote me a while back and they were dead happy to install one anywhere, whereas this dude is struggling to work out how he can sell me his multi-££££ product. I trust him a lot more.

I don’t live in a quiet country retreat, rather the opposite, but I’m concerned about getting something that ends up being bloody annoying for both me and my neighbours. Hence wanting views and anyone who has actually used one!

Noise is an emerging issue with ASHPs and the guidance around it is evolving due to issues arising in the field.

Last thing you want is a stat nuisance case with your neithbour over ASHP noise

The IOA published some guidance for consumers and installers in Nov 22, which is available here

It would be useful if you know the typical night time spl outside your bedroom window to give you some context on the potential for disruption from the ASHP. The apps for phones arent 100% accurate, but can give you a useful indicator within a couple of dB

Best of luck


It’s under review this summer I expect they will increase the maximum as most heat pumps I’ve had to measure have been between 50 and 63 dB . The only issue I’ve had is when it’s a rural setting and ambient dB is much lower particularly in summer


Is it possible to install an ASHP on a (flat, obviously) roof?

Would noise / vibration / wevs drive me nuts?

One of my neighbours had something installed last summer that you can just about see from the main road. However it could simply be an aircon unit (way to go you dobbers, use more energy to counteract the effects of using too much energy).

Less by the fan than next door’s kitchen extractor.


This is with a Mitsubishi Ecodan which has less whizzy app stuff but solid basic engineering.

I think it might make sense to wait for new products. Surely with the extra attention the noise is getting, manufacturers will start making larger units that reduce reliance on the fan? As it is, bigger generally means noisier due to the extra fan.

I want something like the CPU coolers I used to use: the size of a Coke can with a fan that is completely silent. Possibly inside a damped case!

I recall there was a recent consultation on it, so we shall await the revised requirements and guidance

IOA response to recent consultation on ASHPS

Our neighbours, next but one, had one of the newer units installed, about a year ago.
I walk by it in all temperatures, so from working hard, to ticking over.
I find it inoffensive, my neighbour two doors down, doesn’t agree.
I spent many years living with a/c units, and find them easy on the ear.
I think much of this comes down to what you are used to. If they are not something you normally hear, the db level is a moot point. It is a noise.


double blind testing of course


They are really not loud until you get a faulty fan motor or the thermistor goes and the unit starts to ice up but you are talking about -5-10 depending on glycol levels. The cold snap in January had my engineers working overtime trying to defrost units, though this was mainly to do with a lot of the units being badly or not serviced at all.
But a a general rule it’s really quite rare to install them that close to neighbours where it causes an issue unless there are existing neighbour issues

We have an ASHP/Hybrid system, which switches between gas and the ASHP depending on cost/efficiency.

It’s quoted at 58dB but its really not noticably loud when its running full chat, inside the other side of the wall, our BMW i4 is louder when pre-conditioning/heating than the ASHP running.
Ours is on a wall, under a car port so keeps it above freezing throughout winter which probably helps.


We have four ASHPs, the three in the pic and one at the other end of the bungo. The big Mitsubushi is air-to-water and serves the underfloor heating. The other three Panny units are air-to-air with internal wall mounted AHUs.
The bungo is detached and the nearest neighbour is about 30 metres away, so we’ve never had noise complaints. However the Panny units are extremely quiet. The Mitsubushi does make some fan noise (the fan is huge) but even with all three units in the pic operating, the noise level is not intrusive.

Most modern “air con units” are actually ASHPs - they will do both cooling and heating.

Since moving to the bungo, I’ve learned quite a bit. I would not recommend an air-to-water system because it is much too expensive to run. Air-to-air is far more efficient, produces instant heating or cooling and is much cheaper to run.


It’s tempting to get a couple of air to air systems just to take the edge off, when it’s cold or hot. Do you find them too drying when heating? I hear that’s one of the concerns with them.

Air-to-air systems tend to de-humidify, whether in heating or cooling mode. Placing a water filled container nearby helps.

The house is already “plumbed” for old-school (gas fired) warm air heating. I am hoping that could be reused.

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Global warming is here, summers will be getting hotter and heat waves longer, so having the ability to cool, especially if it can be powered with solar generation, is a big plus.
The folding glass doors in my listening room are south facing, so it gets ridiculously hot if the sun is out (even in winter) so I considered that having cooling installed was essential.