Rooftop solar is rapidly expanding in the United States, with some estimates claiming that a new system is installed every four minutes. There are numerous reasons for this, ranging from falling prices to generous federal subsidies to novel leasing schemes.
But there’s another, less-discussed factor at work here: Residential solar power is spreading like wildfire. Yes, it is contagious. According to studies, installing solar photovoltaic panels on your roof increases the likelihood that your neighbors will install their own panels.
When compared to a slew of socioeconomic and demographic variables, the number of solar panels closest to a house is the most important factor in determining the likelihood of that house having a solar panel. This is demonstrated in a new study conducted by scientists using satellite and census data from the city of Fresno in the United States, as well as machine learning.
Although it is well known that peer effects are important for making sustainable energy decisions, very high-resolution data combined with artificial intelligence techniques were required to identify the critical importance of proximity. The finding is important for policies aimed at broadening the deployment of solar panels to replace unsustainable fossil-fueled energy generation.
The number of solar panels within the shortest distance from a house is the most important factor in determining the likelihood of that house having a solar panel when compared with a host of socio-economic and demographic variables. This is shown in a new study by scientists using satellite and census data of the city of Fresno in the US, and employing machine learning.
“It’s almost as if seeing a solar panel from your window inspires you to put one on your own roof,” says study author Leonie Wenz of Germany’s Potsdam Institute for Climate Impact Research (PIK). “Of course, one could argue that other factors, such as income or educational background, or word-of-mouth within the same social network, such as a school district, are more important. So we compared all of these different options and were blown away by the results. It turns out that geographical distance is not the most important factor at all. The more panels there are within a short radius of my house, the more likely it is that I will have one as well.”
Peer effect halves over the distance of a football field
“Over the distance of a football field, the likelihood of putting a solar panel on your roof roughly halves,” says Anders Levermann of PIK and Columbia University’s LDEO in New York, who is also an author of the study. “The contagion effect is strongest in a short radius around a home with a solar panel and diminishes exponentially as the panels are moved further away.” It is a remarkably robust feature that is most noticeable in low-income areas.
The scientists simply made the data speak for itself. “We combined population census data for each district with high-resolution satellite data that can identify all of Fresno’s solar panels,” explains PIK study author Kelsey Barton-Henry. “We then trained several machine learning algorithms to discover the relationship between people’s socioeconomic status and their likelihood of owning a solar panel.”
“Seeding solar panels where few exist may flip a community”
“The findings suggest that seeding solar panels in areas where there are few may flip a community,” Levermann concludes. “If more solar panels lead to more solar panels, a tipping point may be reached – a good one this time. From the West Antarctic ice sheet to the North Atlantic Current, the climate system has a number of extremely dangerous tipping points.” Wenz continues, “As a result, researching climate decisions to identify positive social tipping points, both small and large, is critical to ensuring a safe tomorrow for all.”
