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Adding additional Solar Panels to a DC coupled battery system

Solar Photovoltaic (PV)

Last Post by bontwoody 53 minutes ago

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 4 years ago

Posts: 1014

Topic starter 18/06/2026 5:28 pm [#3068]

I am currently in a position where it would be very easy to add additional solar panels to a lean too I will be constructing in the near future.

I have a 2.66 kWp FIT system which has been supplemented by a 4.6kWp East/West oriented system DC coupled with a 10kWh battery and 3.6kW inverter.

The battery and inverter are Huawei and the panels have optimisers.

The extra panels would be West orientated and would be very useful in the winter. Their extra output, probably wouldnt make any difference to my peak output and would be clipped by the HUawei inverter anyway.

Is this a sensible thing to do? Would I have to notify anyone? Would I be better trying to source another battery module instead?

I seem to have a spare MPPT on the inverter so Im assuming the new panels are just in a single string with the optimisers doing their thing?

Or would it be simpler to buy a balcony solar system and plug it in when required??? 🙂

Thanks

This topic was modified 1 hour ago by bontwoody

House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60

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JamesPa

(@jamespa)

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Joined: 3 years ago

Posts: 5049

18/06/2026 5:48 pm

@transparent will have chapter and verse but my understanding is that DNOs care about inverters because they are the gateway to the grid. So if you plug extra panels into an existing inverter without changing its export limits they probably dont care, but if you add another inverter they definitely do. Your FIT provider will care though if the output passes through the generation meter and you may have to do an apportionment.

I suspect a plug in inverter in addition to an existing one would be notifiable to the DNO and if it takes the capacity above 16A per phase (possibly even if it doesn't) would require permission.

As to whether its sensible you need to run the numbers if thats what matters, but overprovision on the DC side is generally recommended (or at worst not deprecated) these days.

Someone else may have a more precise answer referencing the regs, but may basic message is that if you want to be certain of compliance then you will need to do investigation either way.

This post was modified 58 minutes ago by JamesPa

This post was modified 57 minutes ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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bontwoody

(@bontwoody)

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Joined: 4 years ago

Posts: 1014

Topic starter 18/06/2026 5:54 pm

@jamespa Thanks James. The FIT system is totally separate from the additional system, so any changes to the latter wont change its output in any case. My feeling, like yours, was that as long as the inverter limits the output the grid wont care.

I am a bit curious as to why I seem to have a spare MPPT port though as it would have made sense to me to put EAST on one and WEST on the other, even with the optimisers. But them maybe it makes no difference with them in the frame. 🙂