Pramod

Reducing the grid trickle feed amount to zero reduced the daily grid consumption to about 0,4 to 0,5 kWh.

Thanks for your replies, folks. I spoke to the installer and he said that it was OK to set the grid trickle feed to zero, which I have now done. It was previously set to 10W.
I will monitor for a few days and then report back. I have also noticed what @DeonBezsaid, that the grid usage on the Sunsynk Connect app shows as zero.
When I did the installation, the City of Cape Town came by to change the prepaid meter, because they said that if any power was fed back onto the grid from the inverter, it would have locked up the meter that was installed previously. Next step is to wait for them to lift the restriction that forces us to be net consumers, to justify the R12,000 that they want to charge to install a smart meter. They currently pay about R1 a kilowatt hour that is fed back into the grid.