Complementarities in Behavioral Interventions: Evidence from a Field Experiment on Energy Conservation

Last registered on December 11, 2019


Trial Information

General Information

Complementarities in Behavioral Interventions: Evidence from a Field Experiment on Energy Conservation
Initial registration date
December 11, 2019

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
December 11, 2019, 11:46 AM EST

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

Last updated
December 11, 2019, 12:08 PM EST

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


Primary Investigator

University of Oxford

Other Primary Investigator(s)

PI Affiliation
University of Bonn, National University of Singapore
PI Affiliation
Friedrich-Alexander Universität Nürnberg-Erlangen, ETH Zurich
PI Affiliation
Max Planck Institute for Research on Collective Goods, University of Cologne, University of Innsbruck
PI Affiliation
University of Cologne
PI Affiliation
University of Bamberg
PI Affiliation
University of Bamberg

Additional Trial Information

Start date
End date
Secondary IDs
Behavioral policy often aims at overcoming barriers like imperfect information or limited attention that cause suboptimal consumer decisions. We argue that when multiple barriers are present, it may be important to overcome them all at the same time, as intervention strategies eliminating only a single barrier can be undermined by the remaining barriers. Thus, behavioral interventions that are tailored towards addressing different barriers each can be complements, in the sense that each intervention is more effective in conjunction with the other(s) than in isolation. We conduct a three-month randomized field experiment on energy conservation in a resource-intensive everyday activity, using two different interventions, home energy reports and real-time feedback, which target information and attention barriers to different degrees, respectively. Crucially, we evaluate both the combined intervention as well as each intervention in isolation.

Home energy reports in isolation fail to reduce energy use despite achieving significant knowledge gains, whereas real-time feedback in isolation induces considerable conservation effects. Strikingly, combining both interventions boosts these effects by over 50 percent, thus showcasing how barrier multiplicity can generate complementarities in behavioral interventions.
External Link(s)

Registration Citation

Fang, Ximeng et al. 2019. "Complementarities in Behavioral Interventions: Evidence from a Field Experiment on Energy Conservation." AEA RCT Registry. December 11.
Experimental Details


We study the effect of two types of behavioral interventions on energy conservation in a specific everyday activity (showering). The first intervention are home energy reports, which are delivered via email and provide information on water and energy use as well as CO2 emissions due to showering. The second intervention is real-time feedback on water use, which is delivered through a smart meter directly in the shower. Crucially, we also evaluate the combined intervention with both home energy reports and real-time feedback.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Energy and water consumption in the shower
Primary Outcomes (explanation)
The primary outcome of interest was whether and how much our interventions induce subjects to conserve resources (energy and water) in the targeted behavior.

Secondary Outcomes

Secondary Outcomes (end points)
Awareness about resource use in the shower (learning), environmental attitude, subjective shower comfort
Secondary Outcomes (explanation)
To assess whether the interventions induced learning about resource use, we ask subjects to estimate their own water use per shower. We collect further survey measures to evaluate whether the interventions had an effect on environmental attitudes, and to evaluate whether there were negative side effects due to lower pleasure of showering (take the fun out of the shower).

Experimental Design

Experimental Design
Initially planned design:
- Real-time feedback (RTF): yes or no
- Home energy reports (HER): yes or no
- If HER yes: Social comparison feedback either exogenous or endogenous (Endo)
-> 6 treatment arms: 1) RTF no + HER no, 2) RTF no + HER yes, 3) RTF no + HER yes + Endo, 4) RTF yes + HER no, 5) RTF yes + HER yes, 6) RTF yes + HER yes + Endo

As we only managed to recruit 361 subjects instead of the planned 600 subjects, we forwent the planned treatment groups 3) and 6) with endogenous social comparison. Instead we implemented a 2x2 experimental design with RTF yes/no and HER yes/no.
Experimental Design Details
Randomization Method
Smart meters with and without real-time feedback are distributed alternatingly from apartment to apartment in each student dormitory. Home energy reports are assigned based on a random draw on the computer.
Randomization Unit
Individual/apartment level (only single-person apartments)
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
361 individuals (intially planned: 600 individuals)
Sample size: planned number of observations
21,000 shower observations (intially planned: 40,000 shower observations)
Sample size (or number of clusters) by treatment arms
90 individuals in each of the 4 groups (initially planned: 100 individuals each, 6 groups)
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?
Intervention Completion Date
March 15, 2017, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
July 31, 2017, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
351 participating subjects, 327 subjects with successful data collection
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
21000 shower observations
Final Sample Size (or Number of Clusters) by Treatment Arms
80-90 individuals per treatment group
Data Publication

Data Publication

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Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials