DamonHD

Ahem ... in summer!

I think that for much of the UK it could be made to work. MacKay did the sums to indicate that only at fairly high urban densities do you need to actively push heat back into the ground in winter. Also see for example: Geothermal pavements: A city-scale investigation on providing sustainable heating for the city of Cardiff, IK Makasis, Nikolas and Gu, Xiaoying and Kreitmair, Monika J. and Narsilio, Guillermo A. and Choudhary, Ruchi https://www.sciencedirect.com/science/article/pii/S0960148123011631 DOI:10.1016/j.renene.2023.119248 Quote: "Depending on ground conditions, 184–345 kWh annually/m road of heat can be provided. Geothermal pavements can reduce anthropogenic heat flux into the ground by 390 MWh/a. In low population density areas 100% residential demand can be fulfilled, overall 23%. Replacing traditional systems can reduce carbon emission by 75%." Basically much of Cardiff's home heating could be provided by shallow geothermal. And this mob looked at Cardiff because the geology is very very well studied. Rgds Damon

I know of no particular reason why the batteries need to be close to the PV if everything is AC coupled and all impedances are in spec. Rgds Damon

My house (EPC A rated) has done nearly 60 years so far. Stick built. Rgds Damon

We have 4 of us in < 80m^2, so maybe you're going to be heating and maintaining an order of magnitude more conditioned space than makes sense, for the planet? Rgds Damon

Maybe see if Octopus can give you a zero or low quote for an ASHP despite your concerns. Maybe a cheap second-hand boiler would last in the interim?

That sounds like an actual rule of thumb... %-P

Gas consumption for 2023 was down to 1275kWh, the lowest ever. Electricity imports were 1364kWh, exports were 1597kWh. There are 4 of us in this house, newly (Feb 2024) given an EPC A. Overall energy carbon footprint for energy is ~200kg for the year. https://www.earth.org.uk/saving-electricity-2023.html Rgds Damon

You haven't seen my hair recently! Baby? I knew I'd misplaced something behind the IWI... (The older one turned 18...) Rgds Damon

50C at -2C outside would probably mean that we could keep all our current rads and be saving significant carbon, but WC would push up our SCoP a lot, I think. Yes, this might be the time to slip in heat meters on SH and DHW if we are going to have some disruption anyway... %-P Rgds Damon

The big chunk of PV helped a lot for both certs AFAIK. At the time of the previous cert I did have two rounds of pressure testing done (to convince myself that the numbers were not just made up). https://www.earth.org.uk/testing-a-house-for-air-leaks.html Rgds Damon

Thus the dilemma in the title of this thread and the linked write-up... Rgds Damon

I pointed out on the screening call that yes I have microbore to one rad (at my desk) but I already run my system at ~45C and it is just about OK at -2C outside. (35C is a struggle at -2C, and our demand is essentially zero at 12C, so a weather comp curve right there if Octopus will fit WC.) The screener also claimed that Octopus is able to work with solar DHW, though will still need to install a tank, so I suspect as preheat only. I also slipped in a message to Greg/Phil as one does checking that there is no problem with me documenting the process however it turns out. Space is very tight here and so I may not get agreement from my other half, never mind Octopus! Rgds Damon

The council estate that the house is on is being redeveloped. https://cambridgeroadestate.com/ My house will be CPOed and knocked down when the final phase is reached. One reason for getting in the Octopus queue is that that gets another huge subsidy on top of the BUS grant. Another is that I have a line to talk to the CEO and CTO. Also I am doing a PhD in decarbonising UK home heating, so having an actual case study in my own home might be handy - really working from home... Rgds Damon

Our combi failed again in mid-December again requiring expensive repairs greater than our annual gas bill, so, in spite of the short expected life of our house before it is pulled down, I booked a slot in the Octopus heat-pump queue: https://www.earth.org.uk/note-on-combi-replacement-dilemma.html#2023-12-13 In order to allow a BUS grant I had our EPC redone. It was B before all the aerogel IWI, and is now what seems to be a good A. Rgds Damon