Messaging and Low-income Solar Adoption

Last registered on February 01, 2025
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Pre-Trial

Trial Information

General Information

Title
Messaging and Low-income Solar Adoption
RCT ID
AEARCTR-0002218
Initial registration date
May 15, 2017

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
May 16, 2017, 12:09 PM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
February 01, 2025, 9:56 PM EST

Last updated is the most recent time when changes to the trial's registration were published.

Locations

Country
United States of America
Region
Connecticut

Primary Investigator

Name
Kenneth Gillingham
Affiliation
Yale University
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Other Primary Investigator(s)

PI Name
Bryan Bollinger
PI Affiliation
New York University
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PI Name
Marten Ovaere
PI Affiliation
Ghent University
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Additional Trial Information

Status
Completed
Start date
2017-05-15
End date
2019-12-31
Keywords
Environment & Energy
Additional Keywords
pro-social, price, information
JEL code(s)
Q4
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
The market for residential solar panels in the United States is growing rapidly, bolstered by substantial government support at the federal, state, and local levels. Yet there are concerns that this support is primarily benefiting wealthier households, due to different electricity rates, liquidity constraints, landlord-tenant issues, length of tenancy, and perhaps even preferences (Borenstein and Davis 2016, Borenstein 2017). This study examines the effect of information provision on the adoption of residential solar panels by low and moderate income (LMI) municipalities. Specifically, we randomize municipalities in Connecticut into those receiving a behavioral intervention focused on "community-based pro-social" messaging and "financial-based" messaging.
External Link(s)

Registration Citation

Citation
Bollinger, Bryan, Kenneth Gillingham and Marten Ovaere. 2025. "Messaging and Low-income Solar Adoption." AEA RCT Registry. February 01. https://doi.org/10.1257/rct.2218-4.0
Former Citation
Bollinger, Bryan, Kenneth Gillingham and Marten Ovaere. 2025. "Messaging and Low-income Solar Adoption." AEA RCT Registry. February 01. https://www.socialscienceregistry.org/trials/2218/history/250795
Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)
In each municipality we are running a behavioral intervention designed to encourage solar adoption. This intervention is called a "Solarize" campaign, and it involves a roughly 18-week campaign, a single chosen solar installation company (based on a competitive bidding process), discount pricing, a kick-off event, solar open houses, tabling at town events, designated volunteer solar ambassadors who coordinate the campaign with SmartPower. The intervention is specifically designed to foster word-of-mouth and social interaction effects.

The difference between the community-based messaging and the financial-based messaging approaches is that all of the materials given by SmartPower to the ambassadors and potential solar customers exclusively uses very different messages about solar PV. Similarly, SmartPower employees are instructed to exclusively lead with a different set of messages in verbal discussion and to instruct the ambassadors to focus on these messages.
Intervention (Hidden)
Intervention Start Date
2017-05-15
Intervention End Date
2018-07-15

Primary Outcomes

Primary Outcomes (end points)
The key outcome variables are solar adoptions, and moderating factors that influence adoptions.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The program will launch in phases. This allows for a greater sample size. In each phase, LMI municipalities will be randomly assigned to one of two messaging treatments arms or a control. The sample size for the first round is 8 treated plus 4 control municipalities. As campaigns are completed in the first round, the second round begins similarly, followed by the third round.

The Connecticut Green Bank collects data on all residential solar installations in the state.
Experimental Design Details
Randomization Method
The randomization was done by generating a random number and then assigning to each municipality. Balance checks were carried out to ensure that the municipality characteristics were similar across treatment and control.
Randomization Unit
The unit of randomization is the municipality itself.
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
30 municipalities
Sample size: planned number of observations
30 municipalities
Sample size (or number of clusters) by treatment arms
10 municipalities receive "community-based messaging"
10 municipalities receive "financial-based messaging"
10 municipalities are in the control
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Yale Institutional Review Board
IRB Approval Date
2016-09-23
IRB Approval Number
1608018306
Analysis Plan

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Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
Yes
Intervention Completion Date
September 25, 2018, 12:00 +00:00
Data Collection Complete
Yes
Data Collection Completion Date
December 31, 2019, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
29 municipalities
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
9 municipalities received self-interest messaging, 2) 10 municipalities received prosocial messaging, and 3) 10 control municipalities
Data Publication

Data Publication

Is public data available?
Yes
Public Data URL
https://github.com/MartenOvaere/Self_Interest_Attracts_More_Sunlight

Program Files

Program Files
Yes
Program Files URL
https://github.com/MartenOvaere/Self_Interest_Attracts_More_Sunlight
Reports, Papers & Other Materials

Relevant Paper(s)

Abstract
This study examines how messaging approaches in a prosocial intervention can influence not only the effectiveness of the intervention but also, contagion afterward. Our investigation focuses on leveraging two motivations for solar adoption: self-interest and prosocial. Using data from a natural field experiment in 29 municipalities containing 684,000 people, we find that self-interest messaging is twice as effective in inducing solar adoption both during and after the intervention. Adoptions under self-interest messaging have 10% higher net present value, but prosocial messaging increases the likelihood that adopters recommend solar to their friends and neighbors. Income moderates the effectiveness of self-interest messaging, performing much better in high-income communities than low- and moderate-income communities. There was no significant difference across income groups for prosocial messaging. These results provide guidance to policy makers aiming to encourage prosocial behavior across all income groups.
Citation
B. Bollinger, K.T. Gillingham, M. Ovaere, Field experimental evidence shows that self-interest attracts more sunlight, Proc. Natl. Acad. Sci. U.S.A. 117 (34) 20503-20510
URL
https://doi.org/10.1073/pnas.2004428117

Reports & Other Materials

Description
Explanation for Departures from Pre-analysis Plan
Citation
Bollinger, Bryan, Kenneth Gillingham and Marten Ovaere. 2025. "Messaging and Low-income Solar Adoption." AEA RCT Registry. February 01. 2025. "Registration Entry Title: Explanation for Departures from Pre-analysis Plan." AEA RCT Registry. February 01 https://doi.org/10.1257/rct.2218-4.0
File
Explanation for Departures from Preanalysis Plan.pdf

MD5: 9cc90c474d24c85e1f790380071856b0

SHA1: 6db6ae1862a736702231a19260ca6949d45e65d5

Uploaded At: February 01, 2025