3.68kW DNO limit DOES NOT relate to the size of the solar panel system. It relates to the inverter's AC output only. Not the amount of DC connected to it.

In the UK with lower average solar radiation, your solar capacity should be 1.5 - 2 times larger than the AC output of your solar inverter.

3.68 kW and below requires a G98 notification. Larger than 3.68 kW requires a G99 application.

Solar panel system size Inverter size G98 or G99 required
3 kW 2 kW G98
6 kW 3.6 kW G98
12 kW 3.6 kW G98
3 kW 5 kW G99
6 kW 5 kW G99
12 kW 5 kW G99

Solar system size is not taken into account by the grid, only the inverter.

The grid or DNO is not interested in the amount of solar connected to the inverter.

Inverters are type tested before being released in the UK to be connected to the grid. As long as they're fully type tested, the DNO will not care how much solar is attached to the inverter, which is then connected to the grid.

Will the inverter work with too much solar attached to it? That's another question, from the DNO's point of view, their concern is the grid - a type tested inverter will not deliver more than stated to the network.

Typically good residential inverters in 2025 have a maximum MPPT voltage of 550V, 16A maximum, meaning in theory, each string could handle 8800W or 17.6 kW. In reality you wouldn't go that large if using a 3.6 kW inverter but it could handle it.


Tip: Do not buy a cheap inverter from wish.com or an unbranded one from eBay. Good inverters are not that expensive and installing one that isn't type tested isn't worth the hassle.

What is the maximum amount of solar I can have and stay below the 3.68 kW limit?

It's not a hard limit, you can make a G99 application and apply to connect a larger inverter.

The maximum amount of solar a 3.6 kW inverter could handle, using the above example, is:

550V (Max MPPT voltage) x 16A (Max MPPT current) = 8800W per MPPT/string.

Therefore 8.8 kW x 2 = 17.6 kW is the maximum amount of solar connected to a 3.68 kW inverter.

You would have a lot of AC clipping so we wouldn't recommend it.

3.68 kW is the highest connection I can have - whats the most solar I should connect?.

It's worth making a G99 application to make sure. It's quite rare not to be given 5 kW.

We'd recommend a 2-1 ratio, although if the inverter size is the limit and you have enough space for a large solar installation - I would recommend going as large as the inverter will allow - usually 12 panels per string (MPPT) - install 10/12 kW and upgrade the inverter once the grid capacity improves.

The other option is to install a 3.6 kW hybrid inverter and a lot of battery storage. Your inverter could send 3.6 kW to the AC side and up to 5 kW to the DC side (batteries), giving maximum generation of 8.6 kW, if there is room in the batteries!

Octopus unplugs MCS certification

Source: eFIXX Youtube. Octopus has enabled non MCS solar installations to access their export payments.

NICEIC and NAPIT already certify and assess their electricians for competence which includes solar PV so is this change an obvious one?

Always use a fully qualified electrician.

Installing 6.2 kW Vs 4 kW of solar with a 3.68 kW inverter

In the example shown (right),we have a south-facing, unshaded 16-panel, 6.2kW system with a good quality 3.68kW solar inverter.

According to the weather station at Birmingham airport, the maximum irradiance the array will receive is 1006W/m2. Irradiance fluctuates significantly throughout the day/year.

Therefore, during the summer we can assume, on a clear day from 12-1 pm the array will produce 6.23kWh. (for illustration purposes, excludes system losses).

The solar panel inverter can deliver 3.68kWh to the AC side.

2.55kWh is ‘AC clipped’ – lost as heat via the inverter and/or module or the maximum power point trackers (MPPT) will turn the amps down.

The simulation software calculates the yearly losses to ‘AC clipping’ for us:

190 kWh is lost per year to AC clipping – worth £6.65 – £32.30 depending on whether or not you can use the energy.

Total output of 6.2kW array (after AC clipping) = 5908 kWh

What if we installed a 4kW solar system instead “because 4 is closer to 3.68”
The same model (right) but with a 4kW system installed with the same inverter.

AC clipping: 0 kWh

Total output: 4095 kWh

Resulting in 1813 kWh less production per year.

Conclusion

Do not worry about AC clipping, install as much solar as the space/inverter will allow.

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