Hi all, I'd really appreciate the input of members here on the best approach to modernising the heating setup for a fairly large property which we're just about to start the refurb on. The house is approx 385m2, dating back to early 1900's and has solid 400mm thick stone walls. A room by room heat loss calulation gave a 26kw heating load at -2c design temp and that includes the feasible fabric upgrades which we have planned. We have an existing array of 8kw solar PV which in the last 12 months generated 6400kwh of leccy. We don't currently own an EV but that's definitely a possibility on the horizon. Current heating and DHW are powered by an ancient oil boiler with open-vented cylinder (albeit with a new burner fitted in the boiler in the last 3 years) and we went through 3500 litres of oil last year (gulp), and that included a period of "just put a jumper on", when prices were at the absolute peak of madness. The hosue is hugely over specced in terms of rads (e.g. living room has a heat loss of approx 2kw but has almost 5kw of rads capacity) Priority number one is to reduce our fuel bills and it seems like a no-brainer to do as much with the fabric as possible and also have an iBoost or similar installed to dump excess PV generation into DHW. Beyond that, I'm really torn as to the best approach in term of the type of system to specify for that kind of heat load. We don't have a huge budget and there's lots of other jobs that need doing so ground source is out of the question. Ideally we'd completely remove any reliance on fossil fuels but it seems that would mean cascading multiple ASHPs to get the KW rating we need, which then becomes quite expensive. I have spotted that Cool Energy do a 3 phase ASHP which goes up to 32KW but it looks to be quite noisy (70dB) and would only just cover the load required. Another option would be the Grant Hybrid, although that would obviously still tie us to oil somewhat.
Thoughts and opinions about the best way to proceed very gratefully received!