@johnmo Interestingly (or possibly not that interesting) but I’ve found a free app called iLet Comfort that has connected to my system and lets me see and control the heating and DHW settings from my iPhone. It also purports to show the COP but I’ve only been using it for a day so that’s to be seen.

We’ve had an influx of new members as we head into the heating season. Welcome everyone.

On that note, if you’ve had a heat pump installed, please can you vote on our poll above.

Octopus - Daikin Altherma 3M 4KW heat pump install - April 2025

My overall experience has been excellent. My house is a fairly straight forward 2 bed mid-terrace with only 5 rads. Heat loss calc was 3.3kw and I had calculated 3.2kw using the Heat Punk website.

I believe I was lucky to get one of the early Octopus quotes to attract customers so I immediately paid my deposit. However the install eventually took almost exactly one year from that date of application through a combination of design changes, planning permission and Octopus process improvements.

Initial survey was long and thorough actually a bit over detailed as the surveyor was new. Second visit was to correct some mistakes and further discuss heat pump and cylinder location. Octopus adamant about installing a Daikin 4KW at the end of the garden (~9m trench) and re-suing the rather small airing cupboard. I pushed for a near house location despite the requirement of planning permission for boundary & noise limits. Plus I wanted to use the loft as the existing storage tanks were sat on a sturdy platform that could be re-used.

Third visit was to confirm new HP location and the viability of using the loft location. By then I'd already made a planning application which was another mini-saga due to three parties making negative comments to my application. I uploaded lots of examples of recent applications plus a nearby 25 house new build estate all equipped with heat pump similar to mine. The planning officer was happy with my application from day one.

Additional requirements from the third surveyor visit included a structural survey and enlargement the loft hatch access. I did the loft hatch myself and boarded all round the hatch in anticipation of the engineers working and hauling the cylinder up to the loft.

Additional visits were mainly electrical checks though I was offered a Cosy 6 alternative during one visit. However a drain cover right by the preferred location quickly stopped that due to the R290 refrigerant limitations.

Actual install took 4 days with a peak of 6 Octopus vans parked on and around my little cul-de-sac. The Octopus engineers were all excellent. One highlight was a discussion between the DNO engineer and the Octopus electrician about who could cut which seal and move which cable within the regulations while splitting the mains supply between the house, EV & heat pump. Bureaucracy!

Only had one follow up as the volumiser became a little noisy after a couple of weeks. Turns out the bleed valve wasn't quite open so an easy fix. The Octopus engineer did a service as well and spotted one rad lock valve was partly closed where they could easily be open in my simple setup. He also spent some time to go through the function and setup of the Daikin.

During the design process 3 of my 5 rads were changed and Octopus stuck to that. I offered to pay for the last two but in the end I just bought a K2 & K3 myself. The K3 was huge and the Octopus engineers kindly helped me to swap that one in the kitchen/diner.

No issues so far though it's mostly been hot water only but I recently enable "pure" weather comp via the Daikin MMI (LWT mode). Installer only menu option.

JT

Thanks @bimbleuk, it must be a difficult location, many visits to get everything perfect we hope. 

Just curious as to whether you had any battery installed? If not, is the pump only running during low tariff periods, or the ROI would not justify a battery?  

@bimbleuk good to hear a good install story!

Posted by: @batpred

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Thanks @bimbleuk, it must be a difficult location, many visits to get everything perfect we hope. 

Just curious as to whether you had any battery installed? If not, is the pump only running during low tariff periods, or the ROI would not justify a battery?  

More like Octopus wanted to fit a Cosy 6 at the end of the garden, avoid planning permission and re-use the tiny airing cupboard. My preference was to install the Daikin 4KW HP next to the house, apply for planning and locate the cylinder on the existing loft plinth. Oh and upgrade all 5 rads while you're at it.

Plenty of to and fro plus some triple checking and from my perspective overzealous requirements. Asbestos testing & structural survey being the most expensive.

Constantly thinking about batteries but solar not worth it as I'd need panels each side to get sun all day. Battery maybe if the HP was expensive, which I'm not expecting. Small house with no outside location suitable. Inside no chance!

Now running "pure" weather comp. No thermostat control. I have a setback for the 4-7pm and night time only. Cosy tariff.

We’re looking to expand our list of recommended list of heat pump installers, but not based on marketing or self-promotion. We want it to come from real homeowners who’ve actually lived with their systems.

If you’ve had a heat pump installed, we’d really appreciate it if you could take a couple of minutes to rate and review your installer. It helps us highlight the good ones (and identify where things can improve).

You can do that here:  https://renewableheatinghub.co.uk/rate-review-your-heat-pump-installer

@solenoid 

Welcome.  I have made some comments in the separate thread you started here

  i have a terrible heat pump from Global Energy Systems. not recommeded.

We’ve now had a few hundred thousand heat pumps installed in UK homes, and after years of reading posts on these forums, emails and YouTube comments, I get the strong impression that a large chunk of homeowners perceive their installs as average.

And that word makes me uneasy, because in practice, average often means cold rooms in winter, big bill spikes during cold snaps, constant fiddling with controls and being told by installers “that’s just how heat pumps are”… after spending £10k–£20k of your own money on an efficient heating system.

That’s not a technology problem. That’s an installatiin and expectation problem.

Heat pumps can be genuinely excellent when they’re designed and installed properly. But far too many systems seem to land in this grey middle ground where homeowners adapt, tolerate and even defend something that probably could (and should) be performing better. There are literally thousands of posts on these forums alone to back that up.

So I’ve just published a video digging into this: why average may actually be hiding underperformance, how we should really be evaluating systems and why we need to stop letting excuses pass as explanations.

If you’ve got a heat pump, I’d really encourage you to vote in the poll at the top of this thread if you haven’t already… not aspirationally, but honestly.

And if you’re unsure which box you sit in… that, in itself, is interesting.

The Vaillant app reports on energy in, yield and heat generated - daily or with some effort, hourly. You might think that Energy out = Energy in + Yield but there's a difference of typically about 3-5% of 'missing' energy so I got to thinking about why.

There is very little discussion anywhere on genuine heat pump efficiency - *not* COP but instead relating to how much energy is returned to the environment by fan motors and compressors running warm and heat exchanger coils being de-iced. The proportion of missing energy that I saw was greater when it was colder which suggested that it measured efficiency to some degree and I could believe that your average modern heat pump could be 95-97% efficient.

Then, there is measurement - measuring electrical energy in is OK but how do you measure heat out?  The answer is by multiplying the flow rate by the difference between flow and return temperatures which means potential errors from two temperature sensors and a flow meter. The effect of the errors will be magnified where it occurs in the small difference between two large quantities.

I'm still trying to find out how you measure yield because what I've found so far says that it is energy out minus energy in but that is a circular definition and clearly it isn't the case here or the figures would add up exactly.

These figures go into calculating the COP and if each of these factors added even 1% to the error then we're looking at several percent uncertainty when quoting COP and this is when using our own data - "4" could be anything between 3.5 and 4.5.  Studies tend to show that manufacturers quote optimistically as well which is another story.  Vaillant seem to quote the COP from the energy out and energy in figures and not the yield which IMHO is the right way to do it.

I thought that all this was relevant in the context of assessing heat pump design and performance so ... enjoy!

@editor 

Posted by: @editor

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We’ve now had a few hundred thousand heat pumps installed in UK homes, and after years of reading posts on these forums, emails and YouTube comments, I get the strong impression that a large chunk of homeowners perceive their installs as average.

I am a little sceptical regarding the assumptions made mainly due a cultural issue. From my experience with other review platforms, sadly British people only publicly voice their grievances with organisations and individuals. If things go well they tend to just smile and get on with their lives and make very little or no effort to give credit where credit is due. Is this out of fear of being accused of "bragging", "showing off", "rubbing the noses in it of those less fortunate" who knows?

My point is, out of the hundreds of thousands of heat pump installations are we only really hearing the problems thus unfairly skewing the results?

Posted by: @editor

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Heat pumps can be genuinely excellent when they’re designed and installed properly.

Out of the hundreds of thousands of machines fitted I would hazard a guess that the vast majority of installs are retrofit.

From my experience retrofitting is a lot more tricky and requires more compromise with each component of the system than the luxury of a brand new design and fit

Unfortunately many installers either do not take the time or have not got the time to get a clear understanding of the heating system they are fitting the heat pump to and this is probably in addition to all the other well documented failings e.g lack of heat loss calculations etc.

My own system from a plumbing perspective was fitted to a good standard but the performance for the first 18 months was substandard to what I was expecting.

It was not until I looked into fine tuning the system myself that I discovered the issues preventing the system from performing to its potential.

The first issue was the radiators required re-balancing again. The balancing was good enough when I had a 26Kw oil boiler blasting through but finer balancing was needed for the heat pump. How many installers have the time to keep revisiting a property to keep tweaking radiators to the required standard?

The  next issue I found was my installer did not appreciate the fact that I had a large number of old T60 and T50 radiators on my system. When these where sized it was in the days when very little or no house insulation was used but now are oversized due to up to date insulation levels. These radiators work best with an average delta T = 10C.

Instead of my installer setting the heat pump to work with this radiator delta T he set the heat pump to delta T = 5C because market dictates that heat pumps work best at this delta T. That maybe fine for the heat pump but what about the rest of the system? The heat pump is only a component not the whole system. 

Another reason he did not change the heat pump delta T was because he did not know or understand (admitted to me on commissioning day) the purpose of the PWM pump and water pump control system which this delta T setting is part of. Why would he, he is a plumber not a system control expert.

So I changed the delta T to 8C to match my old radiators and the result is my flow temperature is closer to what is required and the house now reaches the required 21C where in the past it would struggle all day to reach 20C and possibly 21C just before we went to bed. This change has made the heat transfer from outside into my lounge a lot more efficient and allowed me to more accurately set the flow temperature required instead of trying to run the system hotter in an attempt to reach the 21C internal temperature.

I am now getting a combined heating and DHW SCOP of 4 based on real world measurements.

Just by clearly understanding the existing infrastructure and tuning the entire system to work well not just the heat pump, I feel better results could be achieved. However not all users are technically minded to make the changes themselves and not all installers have the time and in some cases the ability to "think outside the box" on an individual case by case basis. Instead some installers default to "what the market says" which in my opinion is in danger of creating a " one size fits all" scenario.

All based on my personal opinion and experience of course 🙂