Detractors of renewable energy like to state that the Energy Return on Energy Investment (EROI/EROEI) to too low to be workable. And it is true that the EROI of the installed base of solar panels is much lower than that of say hydro power or 1950s oil from Saudi-Arabia. Our estimate would say around EROI=10.
However, there are developments in the works that should make it clear that a vast improvement of EROI is very well possible, if not realized already. Thin film solar is basically an extremely thin layer of a few nanometers active material on an ultra-cheap substrate of for instance plastic. It is not difficult to understand that the energy input of thin film solar will require much less energy than old-school silicium crystal-based solar cells.
As the graph shows EROI values realized for thin film solar is already in the 34 range with further improvement to be expected.