Excellent thread and I’ve been intending to contribute for a while but keep getting distracted.

The consumer side of this equation is the piece I think is being underweighted. This thread has focused on the technical and regulatory levers. But @majordennisbloodnok’s point about the homeowner trust problem is the one that always resonates with me. The staged install model only works if the homeowner understands and accepts what they’re committing to upfront. The moment a distressed homeowner hears “we’ll fix the rest later”, however well-intentioned, a significant proportion will hear “it won’t be quite right to start with.”

The piece @andrewj floated about grant pull-down in advance actually solves this more elegantly than the distress purchase pathway does. It converts an emergency decision made under duress into a prepared decision made rationally. The problem though, is it requires homeowners to think about their boiler failing before it fails, which is not how most people work, and I don’t see how we can overcome this on a mass, national scale.

So the question becomes, can you create a structural incentive to pull that conversation forward? A modest, accessible “home readiness check” grant that doesn’t require a full MCS process and is tied to the property rather than the homeowner (funded as a pre-draw against BUS) could potentially unlock that. It’s not a new idea but nobody has packaged it in a way that reaches the mass market.

The other thing this thread has identified, almost by accident, is the cylinder question. The fact that @ashp-bobba and others are demonstrating that existing cylinders can work with R290 units at elevated flow temperatures is more significant for the distress purchase pathway than it might first appear. If you remove the cylinder replacement requirement from the critical path in a combi-to-ASHP conversion (keeping DHW on immersion temporarily while the heat pump handles space heating) the install time and cost drops.

The MCS-lite accreditation idea is also probably the right call. The existing qualification is calibrated for complexity it doesn’t need for a sub-6kW, 22mm primary, no microbore house.

The question for @jamespa is whether MCS will be a willing partner in designing this or whether it needs to be lobbied into it.

Posted by: @andrewj

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I still think that a distressed purchase install is unlikely but an approach to preparing for the eventuality by pulling down on the grant early could help: it might actually improve the comfort of the existing boiler system and cost the homeowner practically nothing at this stage.

Honestly I cant see how that approach works.  People who think this far in advance will be in the minority, and do we really want the Government to be giving people money to do preparatory work which may never actually translate into carbon savings.  I go back to my starting comment namely that the local plumber will fit a replacement boiler next week (or at worst the week after) and its not the local plumber that needs to change!

Given the discussion here I am not seeing any particularly difficult barrier to the heat pump industry doing the same at least for the <6kW house.  It needs some engineering for sure, and a bit of work on contracts, but nothing beyond the with of a few decent people to work out, and maybe some cost reduction of already-existing technology.

Another poster said that 'they cant imagine it happening'.  To this I would observe that, in the 1980s, I was shown an early GPS receiver.  It required a 6' high 19" rack and the aerial, to be good enough, was on the roof of the building.  Now we all carry one, complete with built in aerial (one of several), in our pockets.  If we can do that then we can certainly make a heat pump system work without lots of per-property bespoke design and engineering, which it seems to me is the major challenge of fitting a heat pump vs fitting a boiler, given that we already have a workforce of people who can bend and join pipes and screw things to the wall.

Posted by: @editor

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The consumer side of this equation is the piece I think is being underweighted.

In fairness I did start the thread with the comment that the local plumber will fit a replacement boiler next week (or at worst the week after) and its not the local plumber that needs to change!  This was 100% focused on the consumer!

Posted by: @editor

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The question for @jamespa is whether MCS will be a willing partner in designing this or whether it needs to be lobbied into it.

We may find out in the next few months if I can get any traction through the Retrofit Steering team

@jamespa, the barrier to the distress purchase isn’t the technology. It’s the system they’re required to operate within.

What actually stops a capable plumber fitting a heat pump tomorrow when a boiler dies? A mandatory heat loss survey. DNO notification that adds weeks/months of lead time. A default assumption that the cylinder needs replacing. And a commercial model that requires a surveyor, a designer, a qualified installer and an electrician where a boiler swap needs one person and one van.

The boiler industry solved this forty years ago. The entire model is built around speed, simplicity and a single point of accountability. Heat pump installation has been built around a completely different model… one designed for complexity and bespoke design, and then applied universally, including to cases that don’t require it. But that’s what’s needed to get BUS money.

And there’s also the gaping issue of a semi-competent (I’m being kind) installer workforce. I recorded a podcast with a Simon Wardle last week (out Wednesday) and he told me how many heat pump installers there in the UK. Fancy a guess? 

@jamespa 

I also think that a tiny number of households prepare for a heatpump install well before the boiler fails, the incentives do not seem to be there. 

The importance of planning, design decisions and installation location aspects cannot be overlooked, it is much more than the hardware. The GPS example above is for a type of product without impact to anyone else except a single individual user, no nuisance, etc... 

A cost effective low disruption installation of a heatpump, next to where the boiler is, has its unique challenges. The unit needs to go outside, which triggers permitted development rights, etc.