I am trying to find how it calculates how much solar will be exported back to the grid. I thought this could only be estimated empirically, but apparently not.
Anyway, it depends on three factors, power consumption, power installed, and average hours of sun per day, or hours per day as a function of time of year. For C=4.5kWh/day and S=5kW and H=4 sun hrs per day, means 90% will be exported back to the grid Y. So Y(C,S,H)= a closed form expression.
How to guess the fuction? I tried array interpolation for a numeric solution, but it complains: independent coordinates must be sorted in increasing order