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Ok thanks, plenty food for thought

So just so I'm clear on options... Option 1: - 18kw 3ph ASHP and UVC in annex supplying heating and hot water for all 3 buildings (annex, house and workshop) Option 2: - 18kw ASHP in annex powering heating for all 3 buildings UVC in garage connected to heatpump supplying annex only UVC in house powered by electric only for hot water in house and workshop Option 3: - 12-16kw ASHP powering house and workshop located at annex 4-6kw ASHP powering annex located at annex UVC in garage connected to heatpump supplying annex only UVC in house powered by electric only for hot water in house and workshop I think that captures it? Question is...does option 2 and 3 still allow for grant? Thanks

Does it count if UVC for annex is still powered by heat pump?

Oh I see…there goes that idea then…

Yeah the MCS installer did the heat loss calcs. I’ve asked him for the detail. Bit rough maths was 12kw for house, annex 4kw and workshop 2kw. I think I’m coming round to idea of UVC in house outhouse. If it’s to be purely electric fed would I not need a heat pump type? I think he had spec’d the uk cylinder elite heat pump one. What abput one ASHP for house and workshop and 1 for annex? But both located at garage…

Well the idea is to have zero equipment in the house so when it's likely knocked down everything can still operate. We did originally consider the ASHP on that side elevation but it's going to be a patio area as well as it gets evening sun. In the outbuilding, yep it will have UFH in the concrete slab and also hot water. A lot of different options to consider...

I'm really appreciating the feedback, thanks. Knocking down maybe in 15 years earliest. Also a possibility we won't. I think regardless of 1 or 2 ASHP, we like the idea of locating heat pump away from house. But yes, it is a lot of money, but idea is we are spending as little as possible in actual house, as for whatever reason the previous owner really over specc'd on radiators. The cold water will likely be mdpe or insulated mlcp as it will be deep enough in trench. The hot water return is therefore in that quad. I've attached a photo to show. So green line is heat pump(s) location, and other side of that wall is where plant room will be. That garage will be converted in to a 2 storey living block, with UFH on ground floor and rads on 2nd floor. It's approx 12x6m. Pink line is trench to the old boiler outhouse where it can easily connect to existing pipework for CH, H and C. It then connects in that outhouse in yellow line out to workshop which will be around 8x5m.

Thanks for the insight. We are fighting a few competing things in coming up with solution. One of the main things is we may knock down and rebuild house in the near distant future. So by housing all ASHP, HW, CW as well as new electric meter, etc in garage annex it somewhat helps with that. If it helps, we are looking at using insulated pipe like this? https://www.flowsupplies.co.uk/shop/if-bq32-32-25-20-isoflow-32-32-25-20-quadruple-heating-sanitary-dhw-160mm-duct-2067?category=21#attribute_values=350,388,454,456 If I wasn't clear, the new workshop/studio is a further 15m to other side of house which will also make use of ASHP with UFH in the slab.

Yes I think so. Why do you ask?

Yeah I will be paying bills for rental for air bnb. the garage annex will be heated from the ASHP as well. the annex is about 20-30 metres from house. The idea is plant room will be in annex. So HW cylinder and power tank will be in there with ASHP nearby outside

Ah I see. That was me being dumb on that front. Yeah it’s MCS install. I’m hoping to get the full 11-12 export given we are moving to three phase. I haven’t done full maths yet to compare export vs HW divert yet. On the HW front. Is there any guidance to help on tank size? In the house we will likely have max of 2 bathrooms. In the annex for rental it was also likely have 2 bathrooms. Is 300ltr too small for this? Thanks

Maybe it's my simple misunderstanding! The ones with twin coil seem marketed at using excess solar to heat up water?

I'm just finalising my new ASHP system to replace existing LPG boiler. I'm also about to get solar installed, with 12kw generation and 16kw battery. It's a larger 18kw 3 phase ASHP as it will be powering heat and hot water to main house, garage annexe and a separate workshop. He's specified 300ltr HW cylinder and 500 litre powertank and pump as our mains pressure is terrible My ASHP installer doesn't seem hugely on board of specifying a twin coil HW cylinder and seems to think a heat pump cylinder would be fine with normal immersion. What is consensus here? Thanks

So had a quote back which was pretty reasonable at £1500 inc vat, but with me doing excavation and ducting. I've attached the plan they sent me. Currently my supply is overhead from the pole and they are mandating it needs to be underground following yellow line. However it's quite a tricky run with lots of concrete. However, I'm now thinking maybe of using the wooden pole near the garage and house the meter, etc in garage or behind garage. I've already got a trench open (in pink line) to then feed back to house. There is also the existing 25m2 armoured cable between house and garage. What are thoughts on reconfiguring and housing in garage? Thanks

Ok thanks for feedback