Apparently in the "flat" design, half of the solar panels are on the back roof of the model house, facing his actual house, and thus likely not getting any significant light at all.
Well he did say in the source article that he moved the test location around a few times, but another flaw is that the height of the solar "tree" means that it would put the "flat" design in its shade at times. I wonder if he controlled for that, although the images would suggest he did not.
