At some point you will have to put some finer criteria on what the goal is. For example, are you trying to desing the most cost effective system, or are you trying to supply the load as much of the time as possible?
It should also go almost without saying that at 150W average load there's pretty much nowhere in the real world that this idea would have a point. But change that to 1500W or 15000W and that may change significantly.
Conceptually, you probably want an inverter(s) whose nameplate is close to the average load being served. If you want more cost effectiveness, you'd connect modules slightly above that nameplate, and if you want more assurance that the load will be served, you'd connect more modules that are higher above inverter nameplate. You don't want to pay for more inverter power that would likely only be used for export.
This approach doesn't necessarily work if the load is much more variable than you've postulated. There is probably a software analysis approach that could handle such situations, but I haven't seen any such product on the market (and I've been keeping my eye out). And such an approach would be way beyond anything that could be described in a forum post.
Jaggedben,
Thank you so much for your extended reaction. I do appreciate that. I also do understand your remarks.
The goal is to design a system that is as much self consuming as possible. So try to limit the export to the grid.
I've seen calculations for this made quite simple like:
The (Max) Load is 150,000 Watt
The performance ration for the PV System is 75%
So the max capacity for the PV System is
150,000 x 1.4 (PR) makes a System with a max capacity of 210,000 kWp
Personally I think that's to simple. First of all all data like load and performance is not static.
I can imagine that oversizing can be more profitable at the end.
The like they sometimes do with clipping, see the attachment. But what is the right formula to calculate the optimal capacity?
Curious about your thoughts on this
Kind regards
B