I currently have about 12 LG solar panels installed on my roof. They only produce about 3kwh at peak sunlight condition even though they are nominally a 4kwh system. It is because of my house's orientation.

I am planning to install a home battery system and expand the solar panel array. I am going to add another 14 LG panels.

The installer told me that I can keep the existing panels. The old and new solar panel systems are not going to be daisy chained. They will each connect to different phase.

I attached a picture to show my current inverter setup.

In the quote, the installer uses a "Fronius, Primo, Single Phase, 5.0kW (INT) 5 kW Inverter"

enter image description here

I simply don't have any knowledge of electrical system to evaluate the installer's answer. I want to see if the StackExchange community may have any feedback or suggest any questions I should ask.

Location: Sydney, Australia

Home battery to be installed: Tesla Powerwall 2

  • The downside is that they will never pay for themselves. Commented Dec 22, 2021 at 5:42
  • That's okay. I should have made it clear that my concern are with the installation and other technical aspect. Commented Dec 22, 2021 at 11:51

1 Answer 1


Solar panels can only be wired in series/parallel if they're identical panels receiving the same amount of sunlight. Otherwise, the whole will be limited by the panel receiving the least sunlight.

So if you have two solar installations in different places, perhaps with different angles and orientations, then you do need two inverters.

Besides, you can't parallel 12 panels and 14 panels, and you can't wire them in series either because with the usual voltage being 40V, that would make too high voltage for one inverter.

Fronius primo is nice, in fact I just bought one, not installed yet. I think it's a good choice, reliable brand. It has a documented interface over the ethernet port, so you can query it and know how it's working and what power it is generating without any cloud garbage. This can be useful if you want to switch loads in your house when there is PV power so you consume what you produce.

Injecting current from both installations in different phases makes sense.

However I don't know what you mean with battery, since Fronius Primo doesn't do batteries. In fact it is an injection-only inverter. If there is a blackout and you lose mains power, it will shut down. This is mandated by law: if the inverter kept injecting power into the mains when it goes down, then workers from the electricity company would get electrocuted when they cut power to work on the lines, and you would be responsible.

So your installer is doing a good job if what you ordered is a system meant to lower your electricity bill. However this will not provide power in a blackout.

The circuit breaker in the picture says you probably live in Europe, so if you've been following the news and you anticipate blackouts, then you need an inverter that will still work without mains. If this is the case, edit the question and @ me, I'll add to the answer, because I had to do all of that last month.

  • Thx a lot for the response. I live in Sydney, Australia. I am planning to add a Tesla Powerwall 2. Since my existing solar panels do not produce enough electricity, I need to expand my solar array. Hence this question. Thx again. Commented Dec 22, 2021 at 1:50
  • OK! I don't know if the Fronius will want to charge the powerwall if the grid is down, so that would be the point to verify...
    – bobflux
    Commented Dec 22, 2021 at 7:59

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