I think the current requirements and installer approach to hot water cylinders creates a lot of unnecessary and avoidable disruption, and cost for homes with existing cylinders.

The standard MCS sizing formula, 45L per bedroom + 1, can result in cylinders much larger than the existing ones, which do not then fit in existing airing cupboards, with installers then wanting to relocate these into bedrooms, garages or other inconvenient spaces with all of the cost and disruption that entails. 

From a homeowner's perspective, when the existing cylinder is set to 60 deg C, and with new R290 heat pumps able to heat an equivalent cylinder to 60 deg C, it seems a bit ridiculous to incur all of that cost for a bit more stored hot water, which many households may not even need. There should be flexibility to use smaller cylinders, or cylinders of equal size to any existing cylinder, that are drop-in replacements for the existing one.

All of the major heat pump installers insist on pressurised unvented cylinders, which then add a bulky pressure vessel and need a D2 drain installing through the house, or even a D2 forwarding pumping adding. A simple vented heat pump cylinder option would be much less disruptive and costly for houses with existing vented cylinders.

The current requirements don't mention heat stores, so these are something of an novel, unusual type solution which most of the big installers don't support yet these look a brilliant idea for lots of households - compact, rapid recovery, great replacements for existing cylinders and for new installs where space is a premium. They need including specifically in the standards so they become a default, acceptable option. 

It strikes me that the UK market hasn't matured yet, this is all simple, obvious stuff which should in place and will need to be put in place if more homes are going to install heat pumps.

@jamespa, that’s a very fair summary and I completely agree that it’s important to recognise positives where they exist. I’m not against innovation or even the idea of simplifying installs. Anything that makes the process smoother for homeowners and easier for competent installers should be celebrated.

My issue, as you’ve correctly picked up, is about messaging and its knock-on effects. Heat Geek’s reach is significant and their words carry real weight across the sector. When they say “Zero Disruption”, that phrasing doesn’t just stay on their site... it seeps into how the wider market behaves. And as we’ve both seen before, less scrupulous installers will take that headline, strip out the nuance and run with it to justify cutting corners. That’s the danger.

But we have to keep holding everyone (not just Heat Geek) accountable for the clarity and honesty of the message, because the downstream consequences of overpromising are significant. Aira is another problem child. 

That’s all I’m trying to do... flag the risks early before we find ourselves back where we were five years ago, untangling the fallout from thousands of bad installs and frustrated homeowners.

Posted by: @temperature_gradient

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I think the current requirements and installer approach to hot water cylinders creates a lot of unnecessary and avoidable disruption, and cost for homes with existing cylinders.

That's a timely reminder on this note... one of the installers I spoke with this weekend suggested (though it's unverified on my end) that for a heat pump installation in the UK, the existing hot water cylinder often needs to be replaced with a 'heat pump ready' cylinder.

The reason isn't a direct building regulation mandate to replace the tank itself, but rather a performance requirement. Heat pumps run at lower temperatures than conventional boilers, so the cylinder's internal heat exchange coil must have a much larger surface area to efficiently transfer the heat and meet the minimum required hot water temperature and reheat times. Using an old cylinder can drastically reduce the heat pump's efficiency, which can violate compliance standards. 

I will look into it this week. 

Posted by: @editor

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Heat pumps run at lower temperatures than conventional boilers, so the cylinder's internal heat exchange coil must have a much larger surface area to efficiently transfer the heat and meet the minimum required hot water temperature and reheat times. Using an old cylinder can drastically reduce the heat pump's efficiency, which can violate compliance standards. 

Yes the heat pump cylinders use coils with high surface areas, but that isn't the problem, the difficulty comes from the MCS standard sizing formula requiring much larger cylinders which then makes finding a suitable location a challenge. 

There's also a bit of a contradiction in objectives, because we're fitting heat pumps to reduce emissions, but if a much bigger cylinder is required and this needs relocating to an unheated garage or attic, that results in several hundred kWh of extra heat loss, wasted each year.

Plus the lack of acceptance/support of more innovative heat-store solutions which do a better job of solving that need for compact, fast re-heating cylinder to fit in the available space.

Posted by: @editor

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Using an old cylinder can drastically reduce the heat pump's efficiency, which can violate compliance standards. 

I will look into it this week. 

That sounds suspiciously like an argument by an installer who just wants to replace cylinders at any cost to the customer, hasn't got a technical argument for what he wants to do, and will happily ignore the same 'standards' when it suits them.

Depending on the circumstances the options are, so far as I am aware:

• Use the existing cylinder and add a phe and circulator pump replacing the coil.  Same or better performance, much less cost and disruption.  Potentially a bit of noise from the circulator pump depending on siting.
• Use the existing cylinder with existing coil, operate heat pump at high temp for dhw production.  Poorer performance, zero cost or disruption but very workable with many R290 heat pumps and quite possibly R32
• As above but combine with use of immersion and/or circulator pump
• Replace cylinder.  Expensive and possibly quite disruptive, but ultimately the best performance with the exception of the first option.  But what's the (carbon/gbp) payback time relative to any of the above?

The trade offs depend on household usage, funds availability, heat pump capacity, nature of any existing cylinder and householder attitude to any noise which a circulator pump may cause.  There are indeed many cases where replacing an existing dhw cylinder is necessary or desirable, but overall this is another example of the homeowner being denied choice for the convenience or profit of installers, unnecessarily pushing up the price of heat pump conversions at the expense of the taxpayer, the customer and the climate.

If you already have a reasonably recent UVC of sufficient size, I think I would argue that replacing it just to get a larger coil is probably the last option to be considered.  Unless you consume unusually large amounts of DHW the payback time is just too long, particularly if you have, or intend to get, a ToU tarrif.

As it happens I did replace my small vented cylinder.  One installer was prepared to reuse it by adding a circulator pump and phe (which is how he, by default, does cylinders for heat pumps) and I am pretty sure another would also have done.    However after discussion I was happy that the usability advantages to me outweighed the disadvantages.  Had it been a recent UVC (say < 10-15 years old), there was no way this would have been the case and thus no way it would have been replaced.

In defence of installers, most presumably dont have a lab in which they can test new ways of doing things, so when expected to guarantee that a particular solution will work will inevitably default to what they have done in the past unless the customer themselves shows an appetite for experiment.  This applies, I'm sure, to other areas and is perhaps a structural issue in the industry.

For those looking to hear Heat Geek's response to this article, Mars kindly offered us a right of reply which you can see posted here:
https://renewableheatinghub.co.uk/forums/government-schemes/very-much-awake-renewing-the-heating-industry-one-step-at-a-time/#post-50468

I think I am somewhere in the middle of @Mars and @JamesPa. As someone who went through the "normal" heat geek design process I can say I would have appreciated some of the features in this zero disrupt version and may have ultimately decided to go that route with heat geek had it been an option a few months ago.

I can say that the careful design process is fine to a point but ultimately we had a budget. Our first quote from heat geek was over £12000 and required virtually all radiators to be changed and was over our budget

I went back to heat geek installer for changes but it took them a long time to make any changes an come back with updated quotes. He blamed the heat geek platform as he said it was difficult to make changes. I am not sure if that is the case or just an excuse.

I would have massively appreciated being able to review the effect of different design temps and efficiencies on the number of radiator changes and also budget so I could easily what "bang for buck" was acceptable for me.

I agree with @Mars it could prove slightly disconcerting initially if people are in the research phase and are expecting quotes at the lower end or with no disruption whatsoever, but ultimately I think as others have said, the more options the better. Most people have a budget for these projects and if they to able to see varying effects on money, potential savings etc if you spend a little bit more or a bit less is useful to every consumer and allows for a number of buying motivations.

I have decided to go for Adia system, but on the same basis - that to reach the ultimate system efficiency will come in stages not immediately but I am happy with that compromise

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For those looking to hear Heat Geek's response to this article, Mars kindly offered us a right of reply which you can see posted here:
https://renewableheatinghub.co.uk/forums/government-schemes/very-much-awake-renewing-the-heating-industry-one-step-at-a-time/#post-50468/p >

Thank you Aadil. We appreciate you taking the time to reply and share Heat Geek's point of view.

Cheaper. Faster. Less Disruptive.

In this episode of Homeowners’ Q&A Podcast, Leah Robson, Mark Hall, Simon Wardle & James Clark dive into Heat Geek's ZeroDisrupt and answer the big question: does it make heat pumps truly accessible to the masses or is it just cutting corners in disguise?

🎧 Watch now:

Can I just say how refreshingly open this podcast was. 

Mars you did a great job of grilling the installers and you were right to do so, yet at the same time the installers stuck to their guns and were clear that the industry has to offer choice and make itself available to customers who don't have unlimited capital funds, and the 'Zero Disrupt' offering is a sound step towards saying to customers that its their choice whether to buy a Porsche or a Ford.   It seems to me that the potential pitfalls were explored well and there was a remarkable degree of candidness.

Perhaps the one thing that was not (at least for me) resolved is what happens if the customer opts for 'zero disrupt' but when the engineer visits to do the survey it becomes immediately obvious it is not practical.  Perhaps Heat geek have the stats to show that this happens sufficiently rarely that it can be dealt with in an equitable fashion, but we don't know and it would be good to have clarity on this.  I would have thought that giving the installer the option to decline to survey following a visit (and to return the survey money which as I understand it is paid upfront) might cover this fairly both to installer and customer.  Perhaps that happens in practice, we don't know.

I do agree with the installers that we need to get out of the 'only the Porsche will do' mentality that is attached to heat pumps.  Of course that will never, ever, be an excuse for poor installs, but it is an argument that there is a valid trade off between high capital expense for lowest possible running costs, and lower capital expense for higher, but still acceptable, running costs, ie customer choice.  That choice must of course be informed by honest representation of the trade offs which the installer has the responsibility to present.

Well done to everyone taking part!

@editor Mars, speaking as a home and heat pump owner, I found myself nodding and agreeing with all those speaker’s comments and observations in that presentation.

I rather felt that you were demonstrating your suspicions and your scepticism of Zero Disrupt type schemes - or were you just playing ‘Devil’s Advocate’ perhaps?

A very balanced presentation I thought and my views on the scheme have been expressed elsewhere so need not be repeated here. Keep up the good work, Regards, Toodles.

Posted by: @toodles

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I rather felt that you were demonstrating your suspicions and your scepticism of Zero Disrupt type schemes - or were you just playing ‘Devil’s Advocate’ perhaps?

Isn't that the job of a robust interviewer?