Crofter

OK I get it now, I looked at the spec of that Solis and it's limited to an input current of 14A. The panels I'm looking at have Imp of 13.5, which seems awfully close. So any attempt to wire in parallel would go way above the max current.

What prevents you from combining the inputs in parallel? Sorry if I'm missing something obvious. E.g. on my old boat I had two 260w panels in parallel, I just ran them to the same input terminals on the MPPT. I had another MPPT which had four 100w panels all in parallel. On a boat parallel is the way to go because of variable shading, the panels can end up with quite different levels of output.

So I looked up that Solis and it's got a 60v startup. I'm used to boat stuff which will kick in at much lower voltages. So 60v means I need to put two panels in series to get above startup. Presumably that means I could have a pair of panels on each elevation, but I'd ideally want separate inverters for them? Nothing is limiting me to 3kw, I'm just trying to keep this system small, simple, and low cost. Anything above what's needed to heat the UVC is likely just going to go to waste. As a holiday house, it is unoccupied throughout much of the day, and it has low heating demand. And as a non MCS install I wouldn't be getting anything for export. I'm a bit sceptical that the current export rates are sustainable tbh and I don't want to build a system based on them.

Good point. I'm playing with PVGIS and wondering about putting two panels on each aspect of the roof. I hadn't considered that this could complicate things. I've heard of micro inverters, would those be useful in this situation? Or, can I just run panels in parallel? On my boat I have always done that, but that's a smaller system.

I doubt I'd bother with secondhand panels, they're the cheap bit after all.

Well that makes me feel a lot better actually. I had my own idea of what to do and every passing joiner who popped in for a nosey said I was doing it wrong...

Fair enough. But I expect that they reuse the same details in places like window reveals, wall/floor joint, etc. All stuff that seasoned joiners probably do in their sleep, but for me doing it for the first time there was a lot of head scratching. MAKAR, in Inverness, are offering an affordable kit for £128k and are claiming that it will cost £5 a week to run.

Thanks both. The property has a completely separate supply with an E7 meter. Random example of a secondhand inverter (hope this isn't in breach of any forum rules, I have no idea who the seller is) https://www.ebay.co.uk/itm/306596178881?_skw=grid+tied+inverter&itmmeta=01KABNM23RJZP4ZYC7R6XJWNQR&hash=item47628e6bc1%3Ag%3Alq0AAeSwWNRpG1Si&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1eDtXN4tIIR6UuOxc%2FS0lIttlUJ0Z7JI8%2BWN6xaqUGAYWWoFtcYpBGviBiu9ELNmvH7YU6aU%2BaBBT3OZ%2FmvQ9XFTDopJQNPu%2FXvJL4716s1gHyn4Jyz6PFu8rGn20ohVw77ZkKLTwxBZt5kHTHuWr7Qh%2FcgOvxjp1dsXSnEoQCVFTtCUgMFnngx0DlpPVO%2FicepK6nrX7HcO6uE76fYuBhxxJttvCDWjrPDtAPGSw%2FcIsMhSKztfxfv0y4X0m4sgwtWgEPTaAC1c37eP83GP%2B0D4lF3%2BWqs%2FbFCZ9nR67Etlw%3D%3D|tkp%3ABk9SR5ai0PXSZg&LH_BIN=1 Likewise the diverters seem to go for about half price secondhand.

Another money saving idea which I like, and I admit that would be a bit of a niche, would be if the government would create a library of free plans and technical drawings that would be guaranteed to pass building standards. I know most people do use architects, ATs, SEs, etc, but for those of us who like to go it alone, it would be very helpful. I'm not saying we'd have to all build the same design of house, but for the finer details of wall, floor, and roof buildup.

We could rejoin the EU and then importing high spec windows and kitchens would be a bit cheaper...

I've been hearing that in my neck of the woods, for a main contractor project, it should be minimum £2500/m2 including fees etc but excluding plot. That's a bit of a jump from when I built in 2016-17, which worked out at about £1000. I was entirely DIY but the small size of the project counted against it- things like kitchens, driveways, septic tanks don't really get any cheaper on a smaller build.

OK I'm not a total newbie, I've designed and built a couple of off grid systems. But this is different. I've got a small all-electric newly built property which needs essentially no heating at all through the summer months. There's a 200l direct UVC in there which currently heats up from an E7 tariff. I'm considering installing a PV system with a diverter, primarily aimed at covering that DHW demand. I'm going to assume that I need about 8kwh/day to heat the tank (incoming 10°, outgoing 60°, two seven minute showers at 10l/min). As it's a holiday let, it's primarily occupied from April-September inclusive. So I'm looking to design a system that can deliver close to 8kwh/day over that period. What I've come up with so far is: 6x 500w panels (£450) 3kw inverter (£300) Diverter (£300) Plus obviously mounting hardware, cabling, isolators, fuses, etc. So I should be looking at not too much north of £1k, plus any labour and fees. I'm considering getting it signed off by a qualified but non MCS sparky. I believe I still need DNO approval though? If I go down this route, would there be anything wrong with using secondhand gear? The panels would probably be either ground mounted, or on a south facing gable (or possibly a combination of both). Playing around with PVGIS, I've learned that my optimal angle is 39° for total annual output, and 74° for the best winter production. Somewhere in-between would give me the greatest number of months which hit my target of 240kwh. All academic if I end up putting panels on the gable, of course. I could think about roof mount as well, but the roof is E-W. It's corrugated steel over timber battens. Anyway like I say, I'm new to this, I might be overlooking something, or overthinking things. Feedback and suggestions would be much appreciated.

Fair point. When we need the most cooling, we're likely to have an abundance of solar production. And heat waves will continue to become worse in the future. It does seem strange that we're getting this press release on the back of rumours about BUS being scrapped. I think the government have been throwing a lot of ideas out to judge reactions, and to manage expectations. E.g. if you spread rumours of income tax rises, then it feels like a win when nothing happens on budget day.

A2A is used extensively in Scandinavia. I fitted a ducted underfloor system last year and I'm very happy with it. It made more sense than installing a wet system from scratch. It doesn't seem beyond the wit of man to sell restricted units that can only operate in heating mode. Mine has never been run in cooling mode. I didn't even fit a condensate drain.

Party might just be getting started: air to air to be added to the BUS scheme! https://www.gov.uk/government/news/discounts-for-families-to-keep-warm-in-winter-and-cool-in-summer