Comment by cycomanic
5 years ago
Well we should ask this for every energy technology and fortunately people have done this. The term for this is energy return on investment (EROI) where solar has between 8.7 and 34 and wind between 10 and 20 (although other literature says 20 to 50). A value 1 means you get as much energy as you invested. So for solar that means you get your energy used for production back in 1 to 4 years.
Source: https://en.m.wikipedia.org/wiki/Energy_return_on_investment
And the EROEI has been increasing, since one aspect of driving these technologies down their experience curves is reduction in inputs, including energy, needed to make them.