This page [0] discusses this question. It's in German but the Google translation is not bad. The energy required to produce both solar and wind energy has decreased significantly in recent years.
Solar power in Germany (the page claims) takes between 15 - 100 months to generate as much energy as producing them takes. I assume 100 is for old panels, and with modern (=more efficiently produced) panels it's more like 15. Wind power takes just 3 - 23 months to establish this "energy payback".
Solar power in Germany (the page claims) takes between 15 - 100 months to generate as much energy as producing them takes. I assume 100 is for old panels, and with modern (=more efficiently produced) panels it's more like 15. Wind power takes just 3 - 23 months to establish this "energy payback".
The page has more detailed figures and sources.
[0] http://www.volker-quaschning.de/datserv/kev/index.php