Heat Pumps - Best option for specification and design.

Hi, We have a Worcester Bosch pressurised system feeding a large insulated tank for hot water. Heating is on demand and splits into 6 zones around the house 4 of those zones are water underfloor heated zones, and the other two are radiator zones around the house. All zones are on NEST controllers (six). Which makes smart control pretty simple. I have just had a 15Kw solar instal and want to drop the last gas appliance out of the house and make the most of the solar, so the heat pump is next.

Should I let Octopus do the whole thing? Or go through heat geeks? I know this isn't the most straightforward install and want to go premium regarding efficiency, but not get oversold on heating capacity.

Any pointers or advice are appreciated! I'm watching lots of bloggers on the subject; thanks.

Get plenty of quotes! Mine have varied from 4k to 12k after the grant for a 3 bed bungalow with varying degrees of help/knowledge/interest all the way from we can’t be bothered to look so won’t quote at all to 2 hours and a very detailed quote. One was a heatgeek guy who came in midrange without enough explanation (why do I need a buffer?).

ANT80 I had a nightmare with octopus trying to get the underfloor manifold working with 3 downstairs zones. Also the were baffled by mixergy hot water tank. In addition to that the logistics department only sent the key items for the engineers to complete the install on day 4 of 5. It took the 3 weeks for them to get it working.

I feel like octopus have recruited so many new engineers they lack the experience for none standard installs. I wish I used heatgeek.

My personal opinions:

You pay a premium for heat geek but they do design the system well and will get a better SCOP than a bog standard installation. Whether you think that premium is worth paying (lower bills over time) is obviously a personal choice.

Octopus are much more down the 'cheap standard install' end of the spectrum.

Do get several quotes and look in particular at things like the assumptions they make about heat loss, required flow temperature and design SCOP. You want a SCOP of at least 3, ideally 4 or more (mine was 2.5 ☹️).
Don't believe anything about "high temperature heat pumps". Heat pumps are most efficient with lower flow temperatures and are thus a good match to underfloor heating. You should not zone your heating, the nest stuff thus should be removed, and instead the heat pump run low and slow with appropriate flow rates to get the desired temperature in all areas. Often you'll need the radiators upgraded with double panel or larger rads to get the desired temperature.

Have a look at some of the heat geek videos on YouTube.

Air to air heat pumps seem to be cheaper to run than air to water and you have the aircon benefit, but they're not eligible for the grant.

Be prepared for a much bigger electricity bill in winter (ours is about £200-250 a month) but almost nothing in the summer (49kWh for hot water only in May 2024 for example). Overall our annual running costs are similar to our previous oil boiler.

You'll probably need to change tariff for the winter, we were on Agile last winter and it worked very well. You are unlikely to have enough battery storage for a heat pump and the home in winter so hence the different tariff.

Evaluate A2A as well as A2W. No grant as already mentioned and no hot water but way more flexible. We run two external pumps with 5 internal units leveraging on 10.1 kwp solar and 19kwh of batteries. We don't pay anything for electricity/gas. The winter bills are covered by the summer export credits with some to spare.

Thanks, guys, that's great advice; I forgot to mention we also have a worcester bosch double hot water solar panel on the roof circulating a 40-degree rise in good sunlight. I have also noticed that Worcester bosch has also announced a 2.5k additional top-up grant started last month. So 10k towards. I think my insulated tank is 190lt. Would they integrate that into a heat pump system and run a constant temperature in there, also utilising solar water heating, I wonder? I think a Heat Geek plus whatever WB will do for free might get me close initially. Then quote of that spec.

Sounds like we are in for some lifestyle changes if we do this. The zones have been our effective way of minimising the gas, with a warm office on its own zone for example. Where you leave the door open and the rest of the hotels sucks the heat out. Interested to see it on balance with our exports etc.

We have 15kw solar but the 10kw battery now seems a little low for this to maximise on heat pump demands. On big sunshine days, we are looking at 85kw production. The house uses around 25-30kw on average when we are in, so balancing export with winter use I guess will be key to success.

That Worcester Bosch offer seems to have quietly disappeared.

I was looking for it last week.

It was here: https://www.worcester-bosch.co.uk/professional/clean-heat-pledge

It was dependent on the Clean Heat Market Mechanism (CHMM) being signed into law.

If it's not a standard install then I would consider a specialist / heat geek. As stated by others, Octopus, BG & the like are only really interested in standard run of the mill installs & will probably struggle with anything that's not in their playbook.
Consider A2A from a reputable AC installer. Yes no grant (but 0 or 5% VAT I think) & you do get the benefit of cooling come summer which you can run for £0 off solar. Plenty of examples of people on YT that have documented their journey & installs with A2A. As for hot water with A2A, some makes are now integrating this with their A2A systems. However, these tend to be smaller systems aimed at 1/2 bed apartments & the like & the cylinders are not that big. Daikin is one that springs to mind. I'm not so sure I would want to put all my eggs in the one basket so to speak & shared operation of the HW with heating & cooling cycles from a single outdoor unit has some restrictions.
If you go A2A maybe consider a dedicated & independent all in in one Hot water heat pump cylinder like the Mixergy iHP. Innovative design vs others that use a non repairable / replaceable condenser. Not the cheapest either.
Another HW option is a Phase Change heat battery like a SunAmp Thermino. Charge it from an A2W heat pump or solar diverter / direct electric & draw instant HW from it when needed. Much more compact than than a water cylinder. No legionnaires' issues or cycles to worry about because it does not store water & ideal for those looking to replace combi boilers who don't have a space for a cylinder.
Plenty of options out their but careful navigation of the best system type for your property / situation & more importantly, selection of the right installer is crucial. There are so many examples of perfectly good kit not working due to poor design / installation.

Oh bugger. Guess the eco experts are behind the curve..

ANT80 We have 15kw solar but the 10kw battery now seems a little low for this to maximise on heat pump demands

Personally I wouldn't get too stressed about the battery capacity to run the heat pump. We have a fairly large house and 2x 9kW ASHP's (probably over specified but it is what it is). In winter daily consumption averages around 20kWh for the heat pump but can get to 70-80kWh on really cold days. I knew I'd never get that much battery storage and if I did I wouldn't be able to charge it up overnight, and anyway it's only needed for half the year at most.
So last winter I looked at all the options and selected Octopus Agile to give me an overall low import rate. We had a 9.5 and a 5.2 battery but in November the 9.5 died and it was only replaced in February so for most of the winter I had just the 5.2 which is really a 4.2 usable. And actually this was pretty much all the battery storage I needed to get through most of the evening peak period running the heat pump and normal cooking etc.

As long as you use good battery automation you don't need nor is it cost justified to have lots of battery storage. I use predbat but plenty of people using wonderwatt or my energy optimiser quite successfully on Agile.