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Solar efficiency

  • 19-02-2022 5:48pm
    Registered Users Posts: 63 ✭✭

    Hi guys. I've just had an 18 panel 7.2KW system installed during the week complete with inverter, optimizers on each panel, battery and an eddi for the hot water (currently disconnected as the stove heats all my water needs during winter months). My question is, even though the weather hasn't been the best for the past couple of days, it appears my system only seems to be generating up to 1.5kw at any one time. I was expecting more given its supposed to be a 7.2kw system. Looking at the usage app on the phone I generated approx 8.5kw yesterday. The panels are positioned 9 on each side of an east/west orientated bungalow in the west of the country. In your opinions, should I expect to be generating more or is this normal for this time of year? I never expected 100% efficiency from the panels even during the summer months, but is this normal for this time of year this this sized system or should I be contacting my installer? I was led to believe a system of this size should be generating in and around 3.5kwh even on bad days


  • Registered Users Posts: 6,213 ✭✭✭Ubbquittious

    Have a look in solar spreadsheet thred & compare yourself to that

  • Registered Users Posts: 2,529 ✭✭✭bullit_dodger

    Your best source of info is really the "daily PV production" thread.

    Daily pv production - Page 60 — - Now Ye're Talkin'

    in there you can find people with similar systems who'll note their production for the days. Really, the best way is to give more than one day. You can't tell from 1 days data as it could be cloudy for you while 10 Km away someone else with a similar system might have blue skies. For example, here is my system stats for Feb.

    Total so far for Feb.....84Kwhr. This is on a 5.3Kwp system, which is orientated directly due east/west.

    8.5KwHr for you yesterday seems to be a reasonable amount. I did 7.33Kwhr, but I have a smaller system. So as a gut feeling, I think your production is fine. The reason of course is that it's not really about a sunny day, but rather the "angle" that the sun hits the panels. Simply put your panels are more "edge on" to the sun in winter with a East/West orientation than they would be with a south facing roof.

    So east/west aren't great in the winter, but come 1st of March -> end of october, you will start to get double digits I reckon.

  • Registered Users Posts: 63 ✭✭Jayo2011

    Reasonable sounds fair enough to me. Just don't want to feel short changed. Out of curiosity, is your system installed long, or just recently with anticipation of a lot more being generated from March/April on?

    Also, do you have a smart meter installed or one of the older analog meters that spin backwards when generating for the grid?

  • Moderators, Home & Garden Moderators Posts: 6,090 Mod ✭✭✭✭graememk

    8.6,kwp here in the NW SW/NE split. Low angle.

    11 today and 6 y'day. What your getting is normal for this time of year.

    I've mine in a year and in the good days in may/June the top of my curve is cut off at the 6kw limit of the inverter.

    On the hotter July Aug days, it just about reaches 6kw.

    On a digital day night meter here.

  • Registered Users Posts: 2,529 ✭✭✭bullit_dodger

    I don't know how technically minded you are, but this site's%20the%20calculator%20for%20Europe

    Gives good (approximate) yields for your location, size and orientation by month. With a split array you'll have to enter in the details twice and sum the two results, but to help you out I put in 3.6Kwp (facing east) into the site for Dublin, and it gives you....

    Obviously since you have 7.2 Kwp .... you would need to add whatever the site tells you your West array will generate. (assuming that 50% of your panels are on east and 50% are west)

    Again, the "Daily PV" thread is probably where I would look. Get to know and understand what to expect.

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  • Moderators, Sports Moderators Posts: 19,024 Mod ✭✭✭✭slave1

    You don't have a 7.2kW system, you are (like it should be) oversized 7.2kWp (potential). You are maxed at your Inverter size which I assume is 6kW. IF all your panels were perfectly S facing at the perfect angle to the sun in May then you would achieve 6kW at a moment in time.

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