Posted by: @majordennisbloodnok

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Nonetheless, assuming you were to get a fairly chunky compliant inverter - let's say a 12 kW inverter - my understanding is that it would be acceptable for the DNO to issue a G98 certificate on the understanding the inverter was limited to a maximum of 3.6 kW export to the grid. 

My understanding is that will require a G99 and a G100. It's common to refuse a large G99 in many areas. It's unfortunately becoming increasingly common to refuse or tightly limit even G100 on fragile rural networks.

I think there are 4 paths

- 3.6kW inverter, G98, no extra plug in stuff. DNO can be unhappy but it's their problem and they'll have to spend some of the shareholders yacht money fixing problems (as slowly as possible).

- G99 to try and get a bit more - but may be refused, may also be ludicrously small like going from 3.6kW to 4kW. That said 5kW for many people is a lot better than 3.6.

- Big inverter, G100 - may get refused but this is the nice grid tie option and gets you capacity, big batteries and options to balance it sensibly with loads of solar easily if you pick the right products.

- Big inverter, don't grid tie, use the grid as input only

The last option you get a big grid forming ("off grid") inverter, wire the grid as generator input, and run the house off it. There's no feeding back into the grid so there are no problems with you overloading anything beyond blowing your house fuse. You need a transfer switch so you can reconnect the house directly to the grid (in case the inverter dies), ground rod and some oddments, and you need an offgrid inverter which can field your house load, and also pass through your house load (so 60-80A). The kit for this is widely available - as you can imagine large rural farms hit this quite often and may well want to go well beyond 16kW with 50kW+ 3 phase options being widely used.

You are essentially then operating an off grid house, whose generator happens to be a wire to the national grid. The downsides of that are that a) your inverter needs to be big enough to field your largest demand so costs more, and b) you won't get any SEG payments, which I imagine isn't going to happen much anyway.

It is possible to build hybrid setups with a mix of on and off grid inverters sometimes sharing the batteries. However that tends to turn into an infeasibly large amount of electrician hours and lots of very expensive blue boxes.