Installing a solar PV system can influence the energy-related behavior of neighboring households, new research has found.

In the research paper “Green spills: Peer effects in pro-environmental behaviors,” available in the Journal of Public Economics, Benedikt Janzen, from Germany’s University of Passau, and Patrick Bigler, from Switzerland’s University of Lausanne, analyzed geocoded data on 260,000 Swiss households in the canton of Bern observed between 2008 and 2019.

Their data combined information on electricity use, solar PV and electricity vehicle (EV) ownership and household characteristics. They also measured the density of nearby PV installations based on the distance between households and solar systems in each year, allowing them to examine how changes in local PV adoption affected neighboring households’ energy behavior.

Janzen and Bigler told pv magazine their findings confirmed that when a household installs a solar PV system, neighboring homes become more likely to install solar PV themselves, adopt an EV and reduce their electricity consumption.

According to figures in the research paper, each additional household reduces their annual electricity consumption by 0.21% for each additional solar PV installation 100 meters away, corresponding to an average annual saving of around 11 kWh. Each additional solar PV installation within 10 meters of a household leads to a 2.1% reduction in annual electricity consumption.

Additional findings add that one additional solar PV array 100 meters away from a household leads to a 0.02 percentage point increase in the probability of solar PV adoption and a 0.01 percentage point increase in the probability of EV adoption.

“Although the magnitude of these effects appears small, they are relatively large in comparison to the baseline probabilities of 1% for solar PV and 0.44% for EV adoption,” the research paper says. “Put differently, an additional solar PV installation at 100 meters distance to a household leads to a significant increase in both the probability of adopting a solar PV and an EV by 2% and 2.3%, respectively.”

When the solar PV array is within 10 meters of a household, the research found the probability of solar PV adoption to increase by 20% and EV adoption by 23%.

“Overall, our research suggests that the benefits of residential solar PV adoption extend beyond the household installing the solar PV system because it encourages other households to act more pro-environmental,” Janzen and Bigler explained.

They also said that they would expect to see similar peer influences in household energy behavior in other national markets, pointing to previous research from the US and other European countries that found solar PV adoption tends to cluster geographically.

“We are among the first to document a spillover on neighboring households’ electricity consumption, but we see no obvious reason why this effect should be unique to Switzerland,” Janzen and Bigler added. “That said, the magnitude and nature of these spillovers are likely to depend on the local context.”

Additional analysis simulated counterfactual adoption patterns by randomly assigning solar PV systems to private rooftops in the study region to illustrate the economic implications of the estimated behavioral changes. This simulation found that the installation of one additional solar PV system can generate a median 0.07 additional solar PV systems, 0.05 additional EVs and 3.7 MWh of annual electricity savings through the peer effects outlined in the research.

Janzen and Bigler told pv magazine their findings indicate that policymakers should take local spillovers into account when assessing policies that encourage residential solar PV adoption.

“Supporting one additional installation may not only benefit the household receiving the support but may also encourage pro-environmental behaviors among neighboring households,” they said. “This implies that the overall benefits of policies promoting residential PV may be larger than what is captured by considering only the direct benefits of supported households.”

Policies around residential solar PV adoption could look to make use of these local social dynamics, they added.

“For example, information campaigns could highlight solar adoption within neighborhoods and facilitate exchanges between households that have already installed PV systems and those considering doing so,” Janzen and Bigler added. “Previous research on such campaigns in the US suggests that leveraging social interactions can indeed encourage the uptake of solar PV.”