SimonD

This is a timely reminder to always run the numbers!

Nowhere near doubling the install cost, partly because it's a self install. It takes me up an inverter size (just), but this is helpful if I can add more panels somewhere else in time. The marginal cost of this is less than £100 for the inverter up-size, plus about £500 in panels and the rails, a few hundred quid maybe. Using planned 510W panels, and only assuming a 30-35% generation ratio, I'd still get about £120-£250 generation gain per year - it's essentially a free way to widen the generation window during the summer due to gains morning and evening. Personally I think the numbers actually stack up as the TOU tariff we're on is 30p peak/kWh A few years ago someone in the solar industry talked me out of accepting a load of panels removed from a commercial installation where they were going through a standard 10 year swap out. I always regret that decision. If I have the opportunity now to build in long-term almost free value, I'm going to take it.

This is pretty much irrelevant tbh. The 'losses' aren't really losses as they go into the heated envelope of the house, so do their bit on contribution. Honestly, I'd wait and see what your heat loss calc says and then review from there as they may be so small if you're going near ph that even a 4kW heat pump would be too big. The other ball to chuck into the mix for a highly efficient house for heating is an exhaust air heat pump, which simultaneously deals with your heating, MVHR and DHW. The you can go multi-split for your air-con. Just make sure that the person doing your heat loss actually understands whole house MVHR and models the heat loss accordingly - lots don't and then calculate normal ventilation losses.

I think I was the one napping. When I was asking about the inverter I was told it had two MPPT strings so I could run the north face on the second, not using MIs - that bit was me being dopey.

Lots of ifs and buts on this one. There are only really three practical ways of moving the heat into and out of the building: water, air, refrigerant. Air specific heat capacity is poor so you need lots of volume and flow, refrigerant needs its own specific pipework, qualifications etc. with lots of limitations to things like pipework length. Water is definitely the most effective way to move the heat. The aircon units will probably also need condensate drainage so added complexity there. I don't think the solution is that simple, or not as simple as the Samsung marketing department makes it look. Maybe okay for a new build, but for a retrofit? I'm not so sure. Like with all these things, the complexity lies more in the cooling than in the heating, especially if you want aircon type cold.

Thank you for the heads up! I just checked back a realised I'd got a couple of things confused. The MIs had been specced donkeys ago for a system that was also on the main roof and included the south face of the garage to account for the predicted shadowing over the year! This plan never got anywhere because the solar designer couldn't find a roofing contractor that would touch our roof and standing seam. So, yes, scrub the suggestion of MIs into the inverter.

There are some installations where installer will put a tee and ball valve off the flow & return outside. They put them before the heat pump isolation valves so you can isolate the heat pump and flush the system through - there are pros and cons to this approach. Just then make sure all the pipework is properly insulated. If you do a fill and flush setup, if you're using mains rather than a pump flushing machine, just make sure you've got easy access to mains water outlet.

Yes, I dread to think about 1) what it'll take to clean a standing seam roof that's been on for 6 years prior to installation and, 2) what it would take to clean to roof when replacing the panels - at end of life or following premature failure. It just took me 20 minutes to clean the old adhesive off a Festool saw guide rail to put a new splinter guard strip on!

Good point. The hybrid inverter I'm looking at has dual string capability, so I can run the south face on one string and then use MIs for a second string without compromising efficiency. These MIs cost a pretty penny don't they so if I can reduce this it would be good!

We're on Octopus intelligent go, so just going through a calculation to understand our usage patterns. We're currently paying average of about 17p/kWh so there's room for improvement. I will look into this.

Would never dream of it - I actually installed the whole roof myself so there is no way I'd let someone touch it in a way that would compromise its integrity. Yes, that's the idea and also because curved standing seam roofs are so common. But following my research I have a feeling the industry has a bit of a problem with the standing seam clamps. Many of them essentially have a lip and use a grub screw, or some other type of vice clamp. The grub screw versions I wouldn't used on mine because this would almost certainly damage the coating and also potentially damage the galvanised surface. So either which way there are risks. Apparently it has been designed for retrofit - but I have some questions about how this would successfully meet the real world of a standing seam! Most other similar products are factory bonded. Apparently fine - it's suggested that it would be fine with my Greencoat PLX roof - but would need to confirm this with the manufacturer as they even had some very clear instructions on the type of sealant that's acceptable in the double seam - which is required in some installation instances where there's a very shallow pitch such as mine.

I've got max 7m x 2.2m minus a velux window which I can easily remove or just panel over on a south facing garage roof and could double that if I went with north facing panels. But this gets shaded by the house in the winter - so could use mini inverters. Then I've potentially got a 3.5 x 2.5, garden room roof but that's right at the other end of the garden compared to the garage. Just accepting the limitations of the garage, plus adding some batteries could be the first step, accepting the limitations.

This is definitely my concern particularly given the length of our panels and the expansion I had to account for when I installed the roof - I just wonder how these pv units can cope with this over the long term.

I'm rapidly beginning to wonder if battery first step is the way to go and just use the TOU we've got and rarely use our full allocation.

Just got an email from my standing seam roof supplier but the followings stick on solar panels. I have no idea about price but given the shape of my roof, this could be a solution. At about 17.5% efficiency are these any good? https://bipvco.com/flextron/