# Rocket stove

A **rocket stove** is a wood-burning cookstove that burns small-diameter fuel at the tips of sticks inside a short, insulated, vertical combustion chamber and chimney, using the chimney's draft to drive a hot, vigorous burn. It was conceived in 1982 by Dr. Larry Winiarski for the Aprovecho Research Center in Oregon, and the design and its associated principles spread worldwide as an open-source clean-cooking technology in the 1990s.<sup>[1](https://patents.google.com/patent/US10495300B2/en)</sup><sup> • </sup><sup>[2](https://aprovecho.org/)</sup>

| Key fact | Detail |
|---|---|
| Invention | Conceived in 1982 by Dr. Larry Winiarski for the Aprovecho Research Center<sup>[1](https://patents.google.com/patent/US10495300B2/en)</sup> |
| Core feature | A hot, insulated, vertical chimney within the stove body that increases draft; no secondary air is added<sup>[3](https://bioenergylists.org/stovesdoc/Still/Rocket%20Stove/Principles.html)</sup> |
| Chimney sizing | Winiarski's principle calls for an insulated upright chimney about two or three times the combustion chamber diameter before heat is extracted to a pot or griddle<sup>[3](https://bioenergylists.org/stovesdoc/Still/Rocket%20Stove/Principles.html)</sup> |
| Measured efficiency | In an Ethiopian water boiling test, a rocket stove reached 32% thermal efficiency against 14% for a three-stone stove<sup>[4](https://www.sciencedirect.com/science/article/pii/S2214157X22005585)</sup> |
| WHO classification | Rocket stoves are listed among intermediate stove technologies using improved combustion chambers; biomass stoves count as clean only at tier 4/5 for PM2.5 and tier 5 for CO<sup>[5](https://www.who.int/docs/default-source/environment-climate-change-and-health/health-in-the-green-economy-briefing-energy-en.pdf)</sup><sup> • </sup><sup>[6](https://www.who.int/teams/environment-climate-change-and-health/air-quality-energy-and-health/sectoral-interventions/household-air-pollution/strategies)</sup> |
| Field result | In rural Uganda, introducing a rocket stove cut kitchen PM2.5 concentrations by 37%, with no statistically significant change in carbon monoxide<sup>[7](https://depts.washington.edu/airqual/Marshall_51.pdf)</sup> |

## Design and operating principle

The defining feature is the insulated vertical chimney. Winiarski's design principles, published through Aprovecho, call for insulating the combustion chamber with low-mass, heat-resistant materials so the fire stays as hot as possible without heating the stove body, and for placing an insulated upright chimney about two or three times the chamber's diameter above the fire before any heat is extracted to a pot or griddle. Fuel is fed so that only the burning tips of sticks are consumed, and air velocity through the fuel is maintained; the draft created by the hot insulated chimney pulls in air and, in Dean Still's description, makes a hotter, more vigorous burn.<sup>[3](https://bioenergylists.org/stovesdoc/Still/Rocket%20Stove/Principles.html)</sup>

A notable point recorded from Winiarski's design is that the rocket stove uses no secondary air. Adding heated secondary air above the combustion chamber did not improve smoke or fuel efficiency in early trials, on the reasoning that enough primary air remains at the top of the combustion zone and added air may only reduce temperatures.<sup>[3](https://bioenergylists.org/stovesdoc/Still/Rocket%20Stove/Principles.html)</sup> Winiarski, Aprovecho's Technical Director, found that rocket-type stoves could be described by ten design principles simple enough to be taught to indigenous stove users, mostly women, who were the experts in using the stoves; he died in 2024 at the age of 81.<sup>[8](https://aprovecho.org/category/rocket-stoves/page/3/)</sup>

## Origin at Aprovecho

Aprovecho Research Center, established in 1976 as a 501(c)(3) nonprofit, works on iterative experimental design of cooking and heating stoves through rapid prototyping and emissions and efficiency measurements. It is best known for bringing open-source clean-cooking technologies to the world: the Lorena stove in the 1980s, then the rocket stove and its associated design principles for wood-burning cookstoves in the 1990s.<sup>[2](https://aprovecho.org/)</sup> The organization has published build plans and manuals for many rocket variants, including a double burner rocket stove, an institutional rocket stove, a rocket stove made from pumice, and designs from Uganda and Lesotho.<sup>[9](https://aprovecho.org/publications/)</sup>

## The 2000 performance experiments

**Quantifying heat losses.** In the summer of 2000, Nordica MacCarty, now Aprovecho's Executive Director, ran a series of 50 rocket stove tests on nine variations of the basic design to determine the location and magnitude of heat losses. On average, convection accounted for 77% of total losses from the stove, radiation for 12%, and storage for 11%; for the pan, convection accounted for 92% of losses, radiation for 6%, and storage for about 2%.<sup>[10](https://aprovecho.org/rocket-stoves/early-rocket-stove-research-at-aprovecho-still-rings-true/)</sup>

The tests yielded a set of results that Aprovecho reports as still valid twenty-four years later:

- Smaller inlets and shorter chimneys were more efficient, but the smaller-inlet stoves took much longer to reach boiling, so they may not suit field distribution if they do not meet user expectations for speed.<sup>[10](https://aprovecho.org/rocket-stoves/early-rocket-stove-research-at-aprovecho-still-rings-true/)</sup>
- Reducing the stove-top to pan gap from 1 inch to 1/4 inch on 4.5-inch-diameter stoves raised efficiency by about 9% in an almost linear relationship, though the 1/4-inch gap sometimes starved the draft and burned out the top front of the feed magazine.<sup>[10](https://aprovecho.org/rocket-stoves/early-rocket-stove-research-at-aprovecho-still-rings-true/)</sup>
- Perlite insulation raised efficiency by about 2 to 5 percent over an uninsulated stove, but heavier super-insulation with two layers of fiberglass blanket decreased performance by as much as 3% because the added mass took longer to heat.<sup>[10](https://aprovecho.org/rocket-stoves/early-rocket-stove-research-at-aprovecho-still-rings-true/)</sup>
- The skirt, a collar around the pan, had the most profound impact: an uninsulated skirt raised efficiency by 10%, and insulating it added another 10%. A 9-inch-chimney stove rose from 21% to 39% efficiency simply by using an insulated skirt.<sup>[10](https://aprovecho.org/rocket-stoves/early-rocket-stove-research-at-aprovecho-still-rings-true/)</sup>

The theoretical ideal that emerged combines a small inlet, a short chimney, perlite insulation, a small stove-to-pan gap, and an insulated skirt, for maximum efficiency, minimal losses, and more complete combustion.<sup>[10](https://aprovecho.org/rocket-stoves/early-rocket-stove-research-at-aprovecho-still-rings-true/)</sup>

## Health context and WHO classification

The rocket stove exists against a large health burden. Worldwide, around 2.1 billion people still cook using solid fuels such as wood, crop waste, charcoal, coal, and dung, and kerosene, in open fires and inefficient stoves; household air pollution from incomplete combustion of these fuels is associated with 2.9 million premature deaths and 95 million disability-adjusted life years in 2021, driving ischaemic heart disease, stroke, lower respiratory infections, COPD, and lung cancer.<sup>[11](https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health)</sup>

Under the WHO Guidelines for indoor air quality: household fuel combustion, a biomass stove is classified as clean for health only if its emission rates meet tier 4 or 5 standards for PM2.5 and tier 5 for CO under the ISO harmonized laboratory test protocol; stoves at tier 3 for PM2.5 and tier 3 or 4 for CO are transitional technologies that provide some health benefit but do not enable achievement of the air quality guideline. WHO lists rocket stoves among the intermediate stove technologies using improved combustion chambers, alongside natural draft gasifiers, and recommends that countries promote the highest performing transitional technologies where cleaner options are inaccessible.<sup>[6](https://www.who.int/teams/environment-climate-change-and-health/air-quality-energy-and-health/sectoral-interventions/household-air-pollution/strategies)</sup><sup> • </sup><sup>[5](https://www.who.int/docs/default-source/environment-climate-change-and-health/health-in-the-green-economy-briefing-energy-en.pdf)</sup>

## Measured performance and field results

Laboratory testing places rocket stoves well above open fires. In an Ethiopian study of sauce cooking, a rocket stove achieved 32% thermal efficiency in the water boiling test (version 4.2.3) against 14% for the conventional three-stone stove, and the authors concluded that shifting from traditional stoves to rocket stoves could mitigate indoor air pollutant emissions and deforestation.<sup>[4](https://www.sciencedirect.com/science/article/pii/S2214157X22005585)</sup> Rocket stoves are also one of the standard stove types in modern comparative testing: a study using the ISO 19867-1 harmonized protocol tested a wood rocket stove alongside LPG, pellet, wood fan, three-stone fire, and charcoal stoves in the same US EPA laboratory, finding tier ratings relatively consistent with the older Water Boiling Test.<sup>[12](https://pubmed.ncbi.nlm.nih.gov/34714622/)</sup>

**Field results are more modest than lab results.** In rural southwestern Uganda, researchers subsidized Ugastove-brand rocket stoves to 54 households in six villages and monitored kitchen air before and one month after introduction. Kitchen PM2.5 concentrations fell 37% (mean reduction 0.68 mg/m3), but the change in carbon monoxide, 8% lower, was not statistically significant. During the acclimation month, 47% of households used the rocket stove primarily, 41% used it in tandem with the three-stone fire, and 12% used the three-stone fire primarily; PM2.5 was lowest in households that primarily used the rocket stove (mean 0.9 mg/m3) and highest among three-stone-fire users (mean 2.6 mg/m3).<sup>[7](https://depts.washington.edu/airqual/Marshall_51.pdf)</sup> An earlier USAID-funded assessment in Ruhiira, Uganda, led by Berkeley Air Monitoring Group with Columbia University's Earth Institute and the University of Illinois at Urbana-Champaign, provided the first field assessment in Africa of a stove intervention's impact on greenhouse gas and health-damaging pollutant emissions, comparing a StoveTec rocket wood stove with the traditional open fire.<sup>[13](https://berkeleyair.com/uganda-impact-of-rocket-stove-on-emissions-of-greenhouse-gases-and-health-damaging-pollutants)</sup>

## References

1. [US10495300B2 - Highly efficient wood stove/heater, Google Patents](https://patents.google.com/patent/US10495300B2/en)
2. [Aprovecho Research Center](https://aprovecho.org/)
3. [Larry Winiarski's Rocket Stove Principles, bioenergylists.org](https://bioenergylists.org/stovesdoc/Still/Rocket%20Stove/Principles.html)
4. [Thermal efficiency improvement and emission reduction potential by adopting improved biomass cookstoves for sauce-cooking process in rural Ethiopia, ScienceDirect](https://www.sciencedirect.com/science/article/pii/S2214157X22005585)
5. [Reduction in emissions from selected fuel/stove combinations, WHO Health in the Green Economy](https://www.who.int/docs/default-source/environment-climate-change-and-health/health-in-the-green-economy-briefing-energy-en.pdf)
6. [Air quality, energy and health: Strategies, WHO](https://www.who.int/teams/environment-climate-change-and-health/air-quality-energy-and-health/sectoral-interventions/household-air-pollution/strategies)
7. [Using objective measures of stove use and indoor air quality to evaluate a cookstove intervention in rural Uganda, Energy for Sustainable Development](https://depts.washington.edu/airqual/Marshall_51.pdf)
8. [Rocket Stoves Archives, Aprovecho (Larry Winiarski obituary notice)](https://aprovecho.org/category/rocket-stoves/page/3/)
9. [Publications, Aprovecho](https://aprovecho.org/publications/)
10. [Early Rocket Stove Research at Aprovecho Still Rings True, Aprovecho](https://aprovecho.org/rocket-stoves/early-rocket-stove-research-at-aprovecho-still-rings-true/)
11. [Household air pollution and health, WHO fact sheet](https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health)
12. [Cookstove Emissions and Performance Evaluation Using a New ISO Protocol and Comparison of Results with Previous Test Protocols, PubMed](https://pubmed.ncbi.nlm.nih.gov/34714622/)
13. [Uganda: Impact of Rocket Stove on Emissions of Greenhouse Gases and Health-Damaging Pollutants, Berkeley Air Monitoring Group](https://berkeleyair.com/uganda-impact-of-rocket-stove-on-emissions-of-greenhouse-gases-and-health-damaging-pollutants)

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*Topic: Encyclopedia › Technology and the built world › Energy technology › Fuels and conversion technology › Titles In to W › Titles Ro to W*

*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*

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