I've just specced up a system to deliver 1-2 KWh per day off-grid, and there are a lot more parts in the system than just the panels.

Apart from anything else, if you save on costs by sticking at 12v, you run quite high current. That 100w panel can fuck you up.

Sure, but the parent poster just wanted 50-100 watts to charge a phone. This just has a USB hub on the back you plug into.