The solar loading factor certainly looks reasonable (but that doesn't mean it is correct, of course). I tested my predicted remaining capacity with and without solar loading:
Battery aging factor adjusted for model - 0.9
Solar loading factor 1.19
Days/week parked in the sun - 4 (no covered parking where I work!!!
Miles/kwh - 5.7
Without solar loading - 8.64% predicted capacity loss
With solar loading - 9.57% predicted capacity loss
I don't have a good handle on my actual capacity loss, except that an incomplete range test to just past LBW gave an extrapolated 106 miles, and theoretically I should get 119.7 miles with a new pack assuming 21 kwh usable, which calculates to a 11.4% loss, for a difference of 1.83%. However, I never tested my Leaf when new so don't have a good baseline.
An additional factor that my model doesn't take account of is the extra heat of 1.6 summers in 16 months, and 1.6 summers worth of solar loading (I have been leaving the Leaf at home this past summer when predicted high is greater than 95 degrees). As with ambient temperature, solar loading is not easy to model for fractional years.
For 5 years, the numbers predicted are 18.27% (no loading) and 20.26% (solar loading)
For 10 years, the numbers predicted are 27.58% (no loading) and 30.57% (solar loading)