Why exported solar units don't pay back like used ones
Exported solar units are credited below the retail tariff, so payback needs a weighted savings rate: self-consumed kWh at retail plus exported kWh at feed-in credit.
Self-Consumption and Feed-In Credit Logic
How self-consumption and feed-in credit mechanisms affect solar system financial outcomes.
The solar yield you pay for may never reach your bill
Your array's yield and your bill reduction are different numbers. What the house uses at midday, and when, decides how much of that yield is worth.