tl_dr__

Is a 10KW system a system that can sustain 10KW? Can it sustain 10KW at night too, or if there is little sun?

What are the numbers in terms of money saved over time? How much power do houses use from the grid, even when they have a 10KW system installed? Do parts of the system have to be replaced, and how often and how much?

Many thanks. In my original question, I didn't mean if the panels could produce 10KW at night, I guess what I meant to ask how much power the system could store, and how much can be drawn from the system at any given point.