Domestic uptake of green energy promoted by opt-out tariffs

Motivating individuals to choose energy from sustainable sources over conventionally produced power constitutes one of the biggest policy challenges for societies(1,2). Here we present the results of a randomized controlled trial in Germany that tested the impact of default rules (that is, a type of 'nudging') on voluntary purchases of 'green' energy contracts that entirely stem from renewable resources. Setting the default choice to more expensive 'green' energy (that is, where consumers have to actively opt out if they do not want it) increased purchases of such nearly tenfold. Furthermore, county-level political preference for the green party uniquely predicted behaviour in the absence of the nudge, suggesting that default setting potentially overrules motivational aspects of green energy purchases. In follow-up experiments, we provide further evidence that the effect does not seem to be driven by unawareness. Summarizing, the present research provides an example of using behavioural science(3-9) for climate change mitigation and shows alternatives to the use of subsidies or other economic incentives.