Hello. Off-gridders need not worry. The proposed 'back-up' tax is to raise funds to pay for infrastructure. Grid  connected solar uses the grid as backup - hence the title 'backup tax'. Off grid solar uses batteries. The authorities worry that if every house on an urbanisation has grid connected solar, the grid could not cope.
Also the electricity companies will lose a lot of money
This is completely opposite to the view of grid connected solar that is taken in the rest of europe