From Green Users to Green Voters

We estimate the effect of the diffusion of photovoltaic (PV) systems on the fraction of votes obtained by the German Green Party. The logistic diffusion of PV systems offers a new identification strategy. We take first differences and instrument adoption rates (i.e. the first difference in the diffusion level) by lagged diffusion levels. The existing rationales for non-linearities in diffusion, and ubiquity of logistic curves ensure that our instrument is orthogonal to variables that directly affect voting patterns. We find that the diffusion of domestic PV systems caused 25 percent of the increment in green votes between 1998 and 2009.