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Yale University, along with partners at the Clean Energy Finance and Investment Authority, SmartPower, and the NYU Stern School of Business, under the Solar Energy Evolution and Diffusion Studies (SEEDS) program, investigated the effectiveness, cost-effectiveness, scalability, and persistence of novel strategies that leverage social interactions for accelerating adoption of solar energy technologies.


Solarize group-buy programs are rapidly spreading from community to community across the United States. The combination of simple tiered pricing, competitive bidding from solar installers, trusted solar "coaching," community rewards, and fixed decision periods seems to be a win-win for reducing consumer prices and increasing adoption rates. This project rigorously evaluated what works and what doesn't so community solar programs can scale up effectively.


Researchers performed multiple waves of randomized field trials of specifically tailored Solarize programs in conjunction with the 2013 and 2014 Solarize Connecticut programs. Each trial was designed to quantify the effects of subsets of strategies within the suite of Solarize activities. The full study compared the efficacy of Solarize components to one another and to a control group. As part of the study, researchers collected data that traced out the dynamic social network structure that underlies technology adoption decision patterns, then used a numerical model to incorporate this data to predict how technologies, like solar, spread through a community given a series of interventions.


Historically, traditional solarize campaigns have more than doubled the number of solar installations in participating communities over relatively brief campaign periods. Installed system prices from Solarize Connecticut campaigns, in addition, were on average 14% lower than the market rate. Researchers experimentally manipulated the variables of solarize campaigns in order to assess the importance of campaign duration, group-pricing, solar ambassador characteristics, competitive installer bidding through an open process, and the level of competition on the effectiveness of the campaigns, measured through total installations and cost-per installation. The knowledge gleaned from this study will drive the design of future Solarize campaigns to help further reduce balance-of-systems costs within the residential solar PV market. A guidebook is in development that will distill the insights from this research for practitioners and local governments interested in running similar campaigns.