Nudging the Poor: Increasing Energy Efficiency Investments of Low-Income Households

Last registered on January 23, 2023


Trial Information

General Information

Nudging the Poor: Increasing Energy Efficiency Investments of Low-Income Households
Initial registration date
January 18, 2023

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
January 23, 2023, 7:04 AM EST

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



Primary Investigator

ZEW Mannheim

Other Primary Investigator(s)

PI Affiliation
ZEW Mannheim
PI Affiliation
ZEW Mannheim
PI Affiliation
University of Heidelberg

Additional Trial Information

On going
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
In the past years, nudges have gained popularity to alter household energy choices. However, in existing literature, low-income households are generally underrepresented. Yet, in the context of rising energy prices and inequality, it becomes more and more important to understand the barriers to energy efficiency of vulnerable groups. This study addresses such literature gap, by testing the effectiveness of nudges in increasing energy efficiency investments of low-income households. We partner with a nation-wide energy efficiency assistance program in Germany that has assisted more than 400,000 low-income households since 2009. Together we implement a natural field experiment, and test the effects of information letter framings and the provision of reminders on subsequent energy efficiency investments.
External Link(s)

Registration Citation

Chlond, Bettina et al. 2023. "Nudging the Poor: Increasing Energy Efficiency Investments of Low-Income Households." AEA RCT Registry. January 23.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Household requests the voucher to replace the refrigerator (yes/no)
Household replaces the refrigerator (yes/no)
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We conduct a natural field experiment in cooperation with a nation-wide energy efficiency assistance program. The main feature of that program is the ‘Refrigerator Replacement,’ which subsidizes the modernization of refrigeration appliances of low-income households with a 100 euro voucher. Upon eligibility, the household receives an information letter that informs about procedural requirements to claim the 100 euros, and average annual savings from replacement. Following the receipt of the information letter, households have to request the voucher, replace their old refrigerator against a new, energy-efficient refrigerator, and can then claim the payment of the 100 euros.

Our experiment randomizes the presentation of the information letter across three dimensions:
(1) Gain vs. Loss Frame: In the gain frame, both an icon (a purse full of money) and the framing of written information highlight the annual savings from replacing the refrigerator. In the loss frame, the icon shows a purse losing money, and annual savings are framed as lost if the household does not invest.
(2) Personalized information: Instead of presenting average annual savings based on engineering estimates, the information letter presents households the annual savings of households with the same composition as theirs. E.g., a household with two adults and one child is informed about the average annual savings from replacement of other households with two adults and one child, and sees a corresponding family icon.
(3) Reminder: In combination with the information letter, the household receives a haptic reminder (a refrigerator hanger) of the program, and/or is reminded 4-8 weeks after information letter receipt about the refrigerator replacement via mail/telephone.

In total there will be 10 treatment arms (that we will potentially pool): (1) Control/standard information letter, (2) gain frame, (3) loss frame, (4) personalized gain frame, (5) personalized loss frame, (6) gain frame and mail/telephone reminder, (7) gain frame and haptic reminder, (8) loss frame and haptic reminder, (9) personalized loss frame and haptic reminder, (10) gain frame and both mail/telephone and haptic reminder.

We study how this variation of information letter presentation and additional reminders affect (i) voucher request and (ii) refrigerator replacement probability.
Experimental Design Details
Randomization Method
Randomization programmed in data base of the energy assistance program.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
2100 individuals (based on program participation rates in past years)
Sample size: planned number of observations
2100 individuals (based on program participation rates in past years)
Sample size (or number of clusters) by treatment arms
210 individuals per arm.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
IRB Approval Date
IRB Approval Number


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials