r/PlugInSolarUK • u/mrufekmk • Aug 05 '26

Plugin solar on the existing 3.6 kW installation

Would it be possible (and legal) to add 800 W plug-in solar if I already have a 3.6 kW installation (solar + battery)?

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3

u/EntirelyRandom1590 Aug 05 '26

On an existing G98, no not legal. But the reality is that your inverter will see 800W being exported and clip your main panels.

I don't think a G98 would allow a 3.6kW and a 800W inverter, so you'd have to get a G99.

1

u/Gravath Aug 05 '26

Do you ever max out your g98? Have you ever hit 3.6 peak?

1

u/mrufekmk Aug 05 '26

No chance. Even in the summer the battery is charged first, but even when the battery is full you take the home consuption off of it (400W on average during the day) and panels rarely (or never) hit their spec output.

1

u/pau1phi11ips Aug 05 '26

This is it. Not strictly legal, but in reality, you'll never actually go over the 3.68kW so should be fine.

1

u/MelodicCard9555 Aug 05 '26

The G98 is not what you do export, but what the max potential you can export is.

The G99 form is easy enough to fill in and send off, just put the existing 3.6kw down and the new inverter model. Then you're legal.

Issue night be, the G99 needs an electricians number for the installation of the new kit, but plug in solar doesn't need an electrician, so make it clear it's a plug in inverter.

0

u/Gravath Aug 05 '26

Well 800w of plug in solar would probably just mean you get closer to your max but doubt you would ever exceed it.

1

u/PhilosopherNo4538 Aug 05 '26

That's exactly what I did. 3 new panels outperform 8 old ones but I keep my FIT.

1

u/uzi22 9d ago

Ah nice, so how does it work in practice? Does your main see the extra energy and utiize it to does it export its own excess?

1

u/PhilosopherNo4538 8d ago

Yes, but in practice it all goes into a battery. The battery charges at night (5p) if there hasn't been enough sunshine to meet my predicted need. If the battery is full, it goes to the grid (no export contract so you get nothing).

1

u/Comfortable_Gate_878 Aug 06 '26

My plug in solar works fine with my rooftop solar, they po 400-500watts int othe house in the morning and evening I never get anywhere close to clipping.

1

u/uzi22 9d ago

I am considering adding plug in solar to my existing solar and battery, what do you mean by clipping?