Customers of Swiss electricity providers had a choice between „green“ and „grey“ energy. In contrast to grey energy, green energy is neither generated by fossil fuel nor by nuclear power. However, customers had to pay a slightly higher price for ecofriendly green power than they had to pay for grey power. The price difference is about 4 % for households and 5 % for businesses (0.01 of 0.25 Swiss Francs per kWh for households and 0.01 of 0.18 for businesses). There is no difference in the private utility of green or grey electricity. Hence, choosing green energy is a contribution to the collective good of a better environment with less risky nuclear energy. Households and businesses alike face a social dilemma with the alternatives of cooperation (green energy) or defection (grey energy) whereby the choice of grey energy is a dominating strategy in monetary terms. By this logic it is clearly understandable that the overwhelming majority opted for grey energy.

But there is another psychological factor to be taken into account. In former years grey electricity was the reference category. In previous years several utilities switched the reference category for ordering electricity from grey energy to green energy. Did the change in the default value have an impact on the proportion of customers buying green energy? Many studies report relatively large effects of the default category on behavior. But does the effect persist? And, even more interesting, is the default effect observable for businesses as well as for private households? Economists would expect that businesses act more in accordance with the Homo oeconomicus model than private households. Also, one would expect that customers‘ willingness to order green energy will decline with the amount of electrical energy consumption.

We explored default effects of energy consumption using data from two electrical suppliers. Both companies recorded the energy consumption before and after the intervention, i.e. the switch of the default category from grey to green energy. The novel aspects of our investigation are that we were able to analyze a large data set of more than 250‘000 customers and that the sample included businesses as well as private households. Moreover, we observed the demand for green energy for several years before and after the intervention. These data made it possible to explore the persistency or fading out of default effects. Simple comparison of differences as well as more refined econometric analysis clearly showed that there is even a surprisingly large and persistent effect of a change in the reference category for businesses.