It's generally assumed that it only takes a few years before solar panels have generated as much energy as it took to make them, resulting in very low greenhouse gas emissions compared to conventional grid electricity.
However, the studies upon which this assumption is based are written by a handful of researchers who arguably have a positive bias towards solar PV. A more critical analysis shows that the cumulative energy and CO2 balance of the industry is negative, meaning that solar PV has actually increased energy use and greenhouse gas emissions instead of lowering them.
This doesn't mean that the technology is useless. It's just that our approach is wrong. By carefully selecting the location of the manufacturing and the installation of solar panels, the potential of solar power could be huge. We have to rethink the way we use and produce solar energy systems on a global scale.