Each panel is 150w MAX, it will never get there, but that is the power supply max wattage. This is what we use for estimating how many panels per circuit, etc. The panel will average about 92w, but again, we use the max wattage rating.
We recommend 12 panels per 20 amp circuit at 120V.
We recommend 18 panels per 20 amp circuit at 208V.
These recommendations are based on the max wattage rating and the rating of the power connector for the jumper cables, which is 15 amps. You could put a few more panels per circuit, however, the connectors are rated at 15 amps and we want to stay within that requirement.