Thank you for your answer. I can see that you are helping a lot of people, which must be time consuming.
So this combination will not work if the long term goal would be independent from the grid as the max output of battery is 3kW. is this due to the inverter or battery?
Thats a limitation of the SPH series of inverters, it's what made me look into adding more inverter power and battery storage.
Is it easy to add other brands component to this setup?
Adding another inverter and battery in addition to the Growatt worked for me, after quite a bit of research and a lot of heartache I went for a Victron Inverter and a DIY battery made up from EVE LifeP04 cells. The Victron inverter was in a completely different league from the Growatt, many more variables to set up and a massive support forum out on the net. Both Victron and the forum members were very helpful and my project has run successfully from 24th December, 2022 we used the first charge to cook the Christmas dinner!
The Growatt inverter does seem to play nicely with the Victron, they both share the grid load very well, a slight issue of the Growatt inverter and battery being used to charge the Victron setup but this is easily minimised by adjusting the charge voltage of the Victron inverter. The Victron system also covers the Growatt inverter during it's annoying self test.
This is how a typical month looked before the Victron system was added:-
The yellow line at the bottom very much reduced due to solar and overnight battery charging but still resulted in 65 kWh of peak consumption at the height of the good weather, it got much worse in the winter time, November used 263 kWh of peak rate electricity.
The Victron system was added, the same month this year looks like:-
The small bump on the 28th is in fact off peak use with Octopus Intelligent charging my car during peak times at off peak rates. Total peak energy is very low month on month.
As you can see, minimal peak use and it stays like this winter and summer, the winter time increases the off peak due to overnight charging but thats at 7.5p kWh.