Nice hack. Can it power a fan for a night? That might save you some money in cooling, which would help with payback.

I won't be using it for my apartment but it has great potential for an off the grid light power use workshop. Good job, thanks for showing.

Just a note, the biggest expense these days in solar power installations, home, is the manpower and incidentals needed to install it. Reduce that and solar power replacement begins to look good. As we saw here, where there were no installation costs.