The costs consist of the electricity price * used kWh and feed -in tariff * consumed kWh. These two values ββare then added.
Example:
1 kWh with network cover * 0.28 cents/kWh, results in 0.28 cents.
100 kWh with PV surplus * 0.9 cents/kWh, results in 90 cents.
So the 101 kWh cost you 90.28 cents.