Taking into account the inefficiencies during the sun rising and setting, how many kWh would a 100W solar panel produce over a day?

I'm having trouble computing an actual figure, because all the places I go to just approximate with "Well you get 12 hours of daylight, so you get 1.2 kWh".

What would be the real figure, taking into account that the solar panel would not be generating energy very efficiently near sunrise and sunset. This is assuming that the solar panel is on a flat roof, and they remain stationary all day. Lets say this takes place in LA which gets 14.5 hours of daylight on its longest day, and 9 hours of daylight on its shortest day.

Any help would be greatly appreciated.