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Solar panels on multiple roofs?

  • 27-11-2022 11:35pm
    Registered Users Posts: 44

    Ok hear me out and please excuse my ignorance, I can't say I understand all of this but I'm learning. So, my issue is I would like to get Solar PV, but because I'm in a semi-d in a crowded estate, I don't think I have much room on my roof. The roof is east-west facing but my house is at the end of a row, so my side gable is south facing. What I'm wondering is would it be possible to place panels on 3 sides, so that from morning to night I would be generating electricity? Basically, what I'm getting at is that my panels would follow the sun from sunrise to sunset.

    From what I've read, perhaps multiple inverters or optimizers could help here, or am I completely mistaken?



  • Registered Users Posts: 538 ✭✭✭idc

    most 5-6kW inverters available will only support two strings thus that will mean two orientations, but it is possible to take one string and split it into 2 orientations provided all panels have optimisers fitting. There are definieitely other board members who have done this.

  • Registered Users Posts: 1,400 ✭✭✭DC999

    It's deffo worth looking at prices for that setup. It’s more about filling the roof to produce a decent amount (and get paid FIT now) than covered each side. But seems you’re tight on space so you’re going to max it anyway.

    I’ve that same setup on 3 roofs (E, S, W) and it’s a class for us. We filled as much as we could, 16 panels. Don't have a battery and wanted a spread over the day. We used a flat roof to get more. So we’ve actually 4 roofs and the 2 East (main roof and extension) are on a single string. East extension roof has optimisers as it gets shaded early and later compared to the main roof. The S on it’s own string (only fits 3 panels, tiny roof), and W on it’s on string. We don’t have a battery. We have one string spare for a future DIY if I can find the space.

    Option1: Get 2 inverters (with 2 strings each). Downside is means you need 2 inverters, so adds to the cost. They do have single string inverters afaik.

    Option2: 3 roofs on 2 strings. Afaik @slave1 does that. He has 3 roof orientation too I think. So 1 roof is on 1 string, then has 2 roofs on 1 string on optimisers. Means you need optimisers on every panel on that string.

    Option 3: Stay with 2 roofs, but then you lose production.

    Tips I've learned:

    Check how West you are. Mine is actual NW and it produces next to nothing at this time of year as sun never hits it (but it picks up light indirectly as do all panels). But up to the end of Sept of so the NW was giving us power at the end of the day, which is great. So I don’t mind it does little during winter. It pays it’s way from spring.

    One thing to watch, one my smallest roof I can only fit 3 panels and I’ve issues with it starting to produce late as the startup voltage with 3 panels is too low. It still works but starts up later that normal. So get your installer to check each string has enough panels for the startup voltage to kick in once it’s light.  

  • Registered Users Posts: 2,406 ✭✭✭bullit_dodger

    As a subsection to Option 2 (above), you CAN have three roofs on 2 strings..... without optimizers.

    • South on one string by itself
    • East & West on the same string, NEED to have the same number of panels on east and west and they need to be the same make/model. You connect the panels on east and west each in series, and then you connect the two outputs in parallel into the string input into the inverter.

    Couple of things to be aware of. I'm assuming you don't need optimizers for other reasons (chimney etc), and you will need to look at the power limits (specifically the wattage) on the inverter. Usually we're limited by voltage, but when you parallel the roofs you will most likely hit the current limit easier.

    To be fair, while I'm mentioning it that it's possible......occams razor will invariably be deployed by your installer and they won't "support" it. But if you were doing a self-install.....