I don't know that you mentioned how many inverters you have, but you could have one or two. What the other posters are referring to is that inverter size is always some fraction of system size. In my case its 16.32 kw system with two 7.6 inverters.
Those in the know would say that 15.2 inverter capacity on a 16.32 system is "more" inverter capacity than you need, but its fine by me (since I wouldn't have saved much by asking for a smaller inverter) and I plan on adding panels at some point now that I see the size of the system.
Next up, if you require 100 to 120 per day you should have gotten the largest size system in the first place. My 16.32 in so cal does not get over 100 per day all year. Sure, over 100 on the best days, but not all.
Next, next up. Your original question. Even on the days my system produces 120, it never reaches 16.32. The best hour is around 12. something. But you get to 120 by having 14 hours of daylight and maybe six hours of production over 10? Today I will get around 75 and only three hours of production were 10 or above.
Next, next, next up. Now that you don't worry about reaching the system size in terms of production, what do you, or should you, get? Its all about location of your house, roof angle, and shading, and how the panels are arranged.
Finally, your last question is sort of the least relevant. Those numbers are what the PWs can put out. Its certainly "relevant" but other than when A/C is starting up, your PWs are hopefully not outputting 15 continuously. I mean, at 15 they would only last like two hours and a bit allowing for a 20% reserve.
What actually happens is, that you will figure out what your house draws at night, average. For us its about 1.5 to 2.5 kwh. Then, do the math, ten hours of that is 15 to 25 kwh. If you have a 20 percent reserve, subtract 8 from your 40.5 and its 34. Remember, I used ten hours to make the math easy, during winter you are going to have 14 hours a day of full darkness and another hour in the morning and evening of not enough sun to power the house.
So, 14 hours at 2 kwh per hour uses up 28 of your 34 available PW.
I mean, 21kwh of surge power? I certainly hope not!
So its:
A. The size of the system has to be converted to your location and roof, then you can get estimated power production.
B. If you use 100 a day you need a big ass system. Probably need a 4th PW. Otherwise, (i) the system won't produce enough to cover house usage, and (ii) part of that means you need to fully charge the over and above house usage, so that (iii) the PWs can make it through the night, or at least the average night, or at least most of the average night.
This is why, when you look at the boards, all the people who already have solar always tell every one to just get the biggest system you can fit on the roof.