Solar Panel Adoption Peer Effects
Yale University / Lawrence Berkeley National Laboratory · Connecticut, United States · 2014
Summary
The Yale/LBNL study documented strong peer effects in solar adoption — neighbors who can see solar panels on nearby rooftops are significantly more likely to adopt. The effect decays with distance and is strongest in the immediate block. The mechanism appears to be both visibility (the panels themselves provide information about feasibility) and social proof (a neighbor's adoption signals that the decision is normal and worthwhile). The finding has been replicated across multiple countries and used to design community-based solar marketing programs that use early adopters as referral sources.
Research question
"Do nearby solar panel adoptions increase the probability that neighbors adopt?"
Methodology
Intervention
Observational study using granular address-level solar installation data to estimate spatial diffusion
Assignment
Instrumental variable / spatial regression discontinuity
Sample size
150,000+ installations in Connecticut, 2005–2013
Primary outcome
Solar adoption rate as function of installations within 0.5 miles
Effect estimate
Each additional installation within 0.5 miles raises probability of neighbor adoption by 0.78 percentage points; effect concentrated within 0.5 miles and decays with distance
Decision
Findings used to design peer-referral solar marketing programs; replicated in California, Germany, and Australia
Result
Positive
Each additional installation within 0.5 miles raises probability of neighbor adoption by 0.78 percentage points; effect concentrated within 0.5 miles and decays with distance
Evidence strength
Moderate
Quasi-experimental design with replication support.
Replication status
Replicated
Institution
Yale University / Lawrence Berkeley National Laboratory
Location
Connecticut, United States
Year
2014
Policy area
Energy & Environment
Mechanism
Social norms