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Oversizing solar panel array relative to the rated size of the inverter

  • 05-11-2021 11:54pm
    Registered Users Posts: 1,443 ✭✭✭

    I didn't realize this was safe to do .. and you can nearly add as many as you want!?

    I have a SOLIS RHI-6K-48ES-5G 6KW HYBRID SOLAR INVERTER with 18 x 345W panels = 6.2KW

    This guy recommends adding 33% more or 2KW ( ~6 more panels ) and I have the space.

    Understand at maximum sun I would be wasting 2KW but for the other 90% of the time I would be gaining.

    This OK ?


  • Moderators, Home & Garden Moderators Posts: 4,904 Mod ✭✭✭✭graememk

    Yep I have 8.64 on a 6kw inverter.

    You just have to be within the max voltage per string (600v) while also taking tolerance and temperature in mind. It's about 12 longi 360w panels per string

  • Registered Users Posts: 1,443 ✭✭✭celtic_oz

    I have 345w JA Monocrystalline panels

    I dont seem to be anywhere near 600V on either string..

    So ok to add another 3 panels to each string giving 12 each?

  • Moderators, Home & Garden Moderators Posts: 4,904 Mod ✭✭✭✭graememk

    It's the open circuit voltage that's on the spec sheet, I'll dig out the formula later that I got from solartricity.

    The open circuit voltage gets higher as the panels get colder. And you take worst case eg minus 20.

    But I'm almost sure you'd be grand with 3 more panels on each string.

  • Registered Users Posts: 1,484 ✭✭✭MAULBROOK

    No harm in going to 8kw on a Solis 6kw Inverter, I hope to be heading that way by the end of the year. From 6.2kw to just over 8kw

  • Registered Users Posts: 527 ✭✭✭zac8

    I have 6.2kw (18 x 345w) with 6kw inverter going in this week and wondering should I see about adding some more panels. I keep reading on here that you can’t have enough. Roughly what should I expect to pay for each 345w panel?

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  • Registered Users Posts: 1,484 ✭✭✭MAULBROOK

    Now is the best time to do it, talk to your installer. it will be cheaper during the install.

  • Registered Users Posts: 2,263 ✭✭✭bullit_dodger

    Expect about €200-250 to add a panel, if your paying north of that.....your being ripped off.

  • Registered Users Posts: 1,939 ✭✭✭SD_DRACULA

    Got 21 x 335w panels on the same inverter and thinking of adding a few more as well, so once you're within the Voc limits you should be good.

    You can use the Solis designer here and match your panels, it will tell you the max panels per string.

  • Registered Users Posts: 1,541 ✭✭✭poker--addict

    if an inverter is sized too big is it right that it’s inefficient on most irish days? I had always thought get an inverter similar to the panel size total but I’m learning that is now wrong- especially in Ireland where we have many days we’re panels maybe be operating at lower out put!?

    7.5kw worth of panels doesn’t need a 6kw panel?

    This used to be a referral link 😎

  • Registered Users Posts: 2,263 ✭✭✭bullit_dodger

    Maybe in the past that might have been true, but inverters are pretty efficient through all the ranges these days and getting better.

    Example inverter efficiency curves for the years 2005, 2015 and 2030 | Download Scientific Diagram (

    The main difference in low light (cloudy) days are the panels and how they deal with diffuse light.

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