“Promotional Campaign Duration and Word-of-Mouth in Solar Panel Adoption” by Bryan Bollinger (New York University, bryan.bollinger@stern.nyu.edu), Kenneth Gillingham (Yale University and National Bureau of Economic Research, kenneth.gillingham@yale.edu), Stefan Lamp (Toulouse School of Economics, stefan.lamp@tse-fr.eu), Tsevtan Tsevatov (University of Kansas, tsvetanov@ku.edu).
Intensive marketing campaigns can be used to increase awareness, consideration, purchase, and word-of-mouth (WOM) of pro-social products. With expanded interest and belief in how social norms and spillovers might be leveraged to combat climate change, it is critical to understand how campaigns designed to leverage such peer effects can be best designed. In this paper, we study the role of campaign duration on solar photovoltaic adoption using a large-scale field experiment, in which we randomly assign communities to campaigns with shorter durations, increasing the marketing intensity to maintain the same total resources per campaign. We find that the shorter and longer campaigns are equally effective while they are running, but the longer campaigns generate more WOM and therefore lead to more adoption post campaign than the shorter campaign. The shorter campaigns led to 34.8 fewer installations per town in the two years after the campaigns concluded, increasing the cost per acquisition from $1,566 to $4,367, the former being substantially lower than installers’ self-reported acquisition costs, and the latter being substantially higher.