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Study Overview

Evaluating the Impacts of Clean Cooking Technology in Laos
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The East Asia and Pacific Gender Innovation Lab (EAPGIL) is carrying out an impact evaluation of more advanced clean cookstove technology—a gasifying wood stove that is considered tier 5 on CO and PM 2.5 to meet WHO guidelines on HAP, and a minimum tier 4 on thermal efficiency, safety, and durability according to the Voluntary Performance Targets set by the International Organization for Standardization (ISO5). This study will contribute to the body of literature by testing in a household environment a different type of cookstove that is more efficient and easier to use. Close to 1,000 households in the Laotian capital Vientiane were randomly assigned to being offered the tier 5 cookstove, with a take-up rate of 63.29 percent. The baseline survey was conducted in early 2022 and the endline six months after roll-out. The primary outcomes of interest are: The primary cook's health, his/her time use, and changes in charcoal consumption. Secondary outcomes of interesty relate to the health of other household members, the primary cook's general life satisfaction, cosy savings, stove adoption and usage, and possible heterogeneity of effects.

Registration Citation:
Health, Nutrition, and Population
Additional Keywords:
Cookstoves, Respiratory health, Lao PDR
Secondary ID Number(s):

Principal Investigator(s)

Name of First PI:
Tobias Pfutze
World Bank
Name of Second PI:
Hillary Johnson
World Bank

Study Sponsor

World Bank
Study Sponsor Location:
United States

Research Partner

Name of Partner Institution:
Ministry of Energy and Mines, Lao PDR
Type of Organization:
Government agency (eg., statistics office, Ministry of Health)

Intervention Overview


The intervention consists of households being given a gasifying wood cookstove that is considered tier 5 on CO and PM 2.5 to meet WHO guidelines on HAP, and a minimum tier 4 on thermal efficiency, safety, and durability according to the Voluntary Performance Targets set by the International Organization for Standardization (ISO5). This clean cooking technology uses pellets that gasify wood and other biomass, rather than burning it directly like in an open fire or in a chimney. The extracted gasses burn much more cleanly than when burning traditional solid fuels. These types of super clean cookstoves decrease emissions by 99 percent, thereby emitting little or no greenhouse gasses, PM 2.5, black carbon, and CO. Households are initially provided with a 30kg bag of pellets (aprox. one-month of consumption) and can subsequently purchase more pellets.

There is reason to believe that this type of technology could produce greater impacts than the less advanced types of clean cooking technologies that have been rigorously tested in household situation. The targeted beneficiary of the intervention is the household’s primary cook. We are looking at her respiratory health, life satisfaction, and time use. We also assess the effect of the stoves on the self-reported health of other household members. Moreover, we look the at usage patterns such as charcoal consumption and follow-up purchases of pellets.

Theory of Change:

The adoption of clean cookstoves is expected to:

- Reduce exposure to 2.5PM particles and improve respiratory health.

- Reduce time spent by primary cook on cooking and related tasks such as cleaning up. As a result, more time is expected to be spent on other activities, including leisure.

- As a result, the primary cook's general life satisfaction is increased,.

- Proper usage of the clean cookstove leads to cost savings for the household.

- Improved indoor air quality has health benefits for other household members.

Multiple Treatment Arms Evaluated?

Implementing Agency

Name of Organization:
South Pole
Type of Organization:
Private for profit organization

Program Funder

Name of Organization:
World Bank
Type of Organization:
Foreign or Multilateral Aid Agency

Intervention Timing

Intervention or Program Started at time of Registration?
Start Date:
End Date:
Evaluation Method

Evaluation Method Overview

Primary (or First) Evaluation Method:
Randomized control trial
Other (not Listed) Method:
Additional Evaluation Method (If Any):
Other (not Listed) Method:

Method Details

Details of Evaluation Approach:

Initially over 1,000 randomly sampled households were interviewed. Of these, 948 were eligible to participate in the project given their monthly charcoal use of at least 20k, their professed interest in the stove, their residential address in the project area, and their willingness to share their contact information with the implementing entity to sell the stove. The sample was then randomly divided into a treatment and control group using random numbers. This resulted in an equal number of 474 households in the treatment and the control group. At the next stage, 300 households were randomly drawn from the treatment group to be first offered the stoves. The remaining treatment group households were ranked to be offered the stoves in a fixed order as other households declined them. All 300 stoves were allocated, resulting in an effective take up rate of 63.29 percent. An in-person interview was the main survey method, but a phone interview was also implemented to contact households that relocated or traveled to different areas during the time of the survey. 

The principal estimation method will consist of the outcome of interest at endline on a binary variable indicating treatment,  its value at baseline, plus control variables. The latter if assumed time-invariant will be drawn from the baseline. Time-variant ones will be included from baseline and endline. This set-up allows for more flexibility than a model in first differences. Given that some households in the treatment group rejected the stove, our principal specification will be 2SLS with assignment to the treatment group acting as a instrument for actual treatment.

Outcomes (Endpoints):
  • Symptoms , activities, and impact subscales of the SGRQ, calculated as described in the manual
  • Overview of health status experienced by the primary cook 
  • Total time the primary cook spends on cooking for the household, washing dishes, and cleaning the kitchen, and gathering fuel in the past 7 days
  • Total time spent preparing meals yesterday
  • Cost of charcoal consumption in past month
  • Charcoal stove is primary stove
  • Charcoal stove is used daily
  • Incidence of eye irritation, headaches, and chest troubles among household members
  • Overall life satisfaction
  • Expected life satisfaction in the next one year
  • Total cost of fuel consumed in the past month
  • Total cost of stove repairs and replacements over the past 6 months
  • Household uses charcoal
  • Household uses firewood, crop residues, twigs or leaves
  • Total expenditures on charcoal, firewood, crop residues, twigs, or leaves
  • Primary stove uses charcoal or firewood
  • Household has not used fuels other than CSI pellets with the stove
Unit of Analysis:
Household level: Primary cook and other members.

Hypothesis A1: Clean cookstoves improve the health of the primary cook.

Hypothesis A2: Clean cookstoves reduce the time spent on cooking and cooking-related domestic work.

Hypothesis A3: Clean cooking technologies reduce use of charcoal

Hypothesis B1: Clean cooking technologies improve the health of household members

Hypothesis B2: Clean cooking technologies may change the primary cook’s general life satisfaction.

Hypothesis B3: Clean cooking technologies lead to cost savings for the household

Hypothesis C1: Households in the treatment group adopt and use the stove

Hypothesis C2: Households use the new stove as an alternative to dirtier technologies

Hypothesis C3: Households use the appropriate type of fuel in the stove

Hypothesis D1: Impacts of clean cookstoves will be stronger for those who used more charcoal at baseline

Hypothesis D2: Impacts of clean cookstoves will be stronger for those whose charcoal stoves were inside at baseline

Hypothesis D3: Impacts of clean cookstoves will be stronger for those who spend more time cooking at baseline

Unit of Intervention or Assignment:
Number of Clusters in Sample:
district level and charcoal consumption (low vs. high), yielding a total of 14 clusters.
Number of Individuals in Sample:
4,891 individual household members, including the primary cook.
Size of Treatment, Control, or Comparison Subsamples:
474 households assigned to treatment and control group. 300 households in assigned treatment group received stove.

Supplementary Files

Analysis Plan:
CSI Preanalysis Plan final.docx
Other Documents:

Outcomes Data

Household surveys conducted in person or by phone. Two rounds, longitudinal. Interviewee was the primary cook. 948 households were interviewed at baseline and 781 (82.38%) at endline. Baseline was conducted between January 14 and April 20, 2022 and endline between November 6 and December 19, 2022.
Data Already Collected?
Data Previously Used?
Data Access:
Restricted -- Access requires a formal approval process
Data Obtained by the Study Researchers?
Data Approval Process:
Data collection required approval by the Laotian government a various levels: Ministry, district, and village.
Approval Status:
Yes-obtained approval and have received the data

Treatment Assignment Data

Participation or Assignment Information:
Data Obtained by the Study Researchers?
Data Previously Used?
Data Access:
Data Obtained by the Study Researchers?
Data Approval Process:
Approval Status:

Data Analysis

Data Analysis Status:

Study Materials

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Registration Category

Registration Category:
Prospective, Category 3: Data for measuring impacts have been obtained/collected by the research team but analysis for this evaluation has not started

Completion Overview

Intervention Completion Date:
Data Collection Completion Date:
Unit of Analysis:
Clusters in Final Sample:
Total Observations in Final Sample:
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Preliminary Report:
Preliminary Report URL:
Summary of Findings:
Paper Summary:
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Data Availability

Data Availability (Primary Data):
Date of Data Availability:
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Other Materials

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Description of Changes:

Study Stopped