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Advice sought, what size PV system

  • 07-04-2022 10:52pm
    Registered Users Posts: 5,083 ✭✭✭

    I've been toying with the idea of a PV system with a battery for a while now.

    I've gotten quotes from two companies, both similar, but sightly different specs.

    Before I post them. What are your opinions.

    I looking for a ground mount system, with a battery, and my daily use is 18kwh.

    I currently have oil heating, but would be considering an air2heat pump in the future.



  • Registered Users Posts: 188 ✭✭connesha

    I’d go 6kw inverter, and as many panels as you can (about 24 is the limit for many panel types)

    Considering usage is higher in winter, especially with HP, chose your panel angle and orientation wisely. This is will make a big difference.

    South facing steep angle is better for winter.

    Or have one string at approx 60 deg, and other at maybe 45. This should get a good winter return (good for Ireland) and have more than enough for summer. There are lots of calculators, see FAQ. Put your angles into that and compare against your monthly usage.

    5kwh battery makes a good difference levelling out gen vs usage, and covering a lot of evening time. 10kwh better, but of course costs more, so you’ll need to see if it’s worth it for you.

  • Registered Users Posts: 5,083 ✭✭✭mikeecho

    Thanks, it's all gobblely book to me, so I've plenty of reading to do.

  • Registered Users Posts: 2,731 ✭✭✭yankinlk

    I am using 20kwh per day. Look up my system size if u want. But if u are ground mounting then I guess u might have an option to build with a better angle to the sun... and as such u could build a smaller system that generates more energy potentially! Read and compare... start with the faq but look at the excel sheet with detail from loads of different builds.

  • Registered Users Posts: 1,554 ✭✭✭celtic_oz

    the panels are the cheapest part .. I would have got more had I known this :

  • Registered Users Posts: 552 ✭✭✭idc

    Thats not actually true, inverters do have limits on input current and voltage so it entirely depends on the panels your connecting as to how many you can connect and how many over the output rating of the inverter. For instance the AlphaESS has a limit of 2 x12A and 580 V. AlphaESS in germany even provide an excel sheet with a selection of different panels so you can work our how many panels in series (or parallel strings) per MPPT you can setup without exceeding these thresholds. But looking at mine it looks like i could have 33% larger input than output. The guy in the video did at one point say you could add 30kW into a 3kW inverter which would definitely exceed the limits

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