Keeping up with the Joneses 2.0: Solar’s Neighborhood Effect

Residential solar adoption is on the rise all across the country. The latest U.S. Solar Market Insight report shows that new home solar installations exceeded 300 MW for the first time in history last quarter and there will be more than 600,000 homes outfitted with solar by the end of the year. We hosted a webinar with Yale University economics professor Kenneth Gillingham on one of the factors behind that tremendous growth.

Solar adoption map Connecticut neighbours

Professor Gillingham and his University of Connecticut colleague Marcello Graziano have examined the diffusion of residential solar photovoltaic systems in Connecticut. While adoption of a new technology is typically related to income or larger population size, they found that solar adoption is decidedly different. Instead, spatial neighbor effects appear to be a more significant factor in residential solar installations.

The data demonstrates a strong relationship between adoption and the number of solar energy systems previously installed nearby. Gillingham noted that the effect of nearby systems diminishes with distance and time, suggesting a spatial neighbor effect conveyed through social interaction and visibility. In other words, solar is contagious and once someone trail-blazes the solar way in a particular neighborhood, others nearby are more inclined to go solar themselves.

These results provide helpful guidance for those who want to see an uptick in solar uptake. Vote Solar is one of a number of organizations nationwide that are working to accelerate this phenomenon through solarize programs that help neighbors and other peer groups go solar together. We think it’s worth giving some good through to other ways businesses, advocates and others can better tap into the neighborhood effect to advance the solar cause.


See slides from the webinar with Professor Gillingham’s here. If you’d like to use any of the material please reference: Graziano, Marcello and Kenneth Gillingham (2014) Spatial Patterns of Solar Photovoltaic System Adoption: The Influence of Neighbors and the Built Environment, Journal of Economic Geography, forthcoming.

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