Did your calculations account for the suboptimal angle of the panels in most balcony solar setups? Most calculators assume the panels are at an optimal angle or on a roof pitch, not vertical like the image in the article.

A setup like the image in the article is going to get much lower than optimal efficiency because the panel is mounted vertically. She could be netting closer to $2-3 dollars per month or even less depending on which way she’s facing.