These numbers change every year, but: solar panels on roofs don't track so they'd be lucky to get 20%, average closer to 12%, efficiency and slowly degrade over a few years. Sun tracking panels can reach a maximum of around 40%, theoretically, but on average more like 20%-30%. You have to subtract the negative impact of creating and assembling the materials from it's lifetime effectiveness, in Germany I believe Hydrogen Steel exists which is much greener than other types of smelting, or otherwise Aluminum is the higher grade material used for such things, and Photovoltaic Panels have a very specialized Glass in most cases that has to be exceptionally clear and strong. If the capacitance of the system is not enough to hold the produced power then an electrical failure will occur, so you must also include large commercial and industrial batteries.

Meanwhile, a Heliostat (a Collection Tower and Mirror Array) out in the desert has a theoretical efficiency just below 70%. Furthermore, if the capacity of the grid fills up then the array can be disable by adjusting the mirrors and excess power can be stored for extremely long periods of time by utilizing molten salt beneath the tower.

These efficiency numbers refer to how much of the heat energy from full spectrum light hitting the array is converted into electricity. Home panels are nice because you can put them on your home