A rocket mass heater (RMH), also known as rocket stove mass heater, is a form of slow-release radiant heating system, designed to primarily heat people and secondarily to warm areas in line of sight around it. Variations of RMH can also be extended for the functions of cooking, heating water, and producing warm air for distribution.[1]

A pebble style rocket mass heater installed at a home in Montana

Rocket mass heaters are developed from rocket stoves, a type of wood-burning stove, and masonry heaters. A primary design of a rocket mass heater consists of an insulated combustion chamber where fuel is burned with high efficiency at high temperature, and a large thermal mass in contact with the exhaust gases, which absorbs most of the generated heat before the gases are released to the atmosphere.[2] According to anecdotes a rocket mass heater might reduce fuel consumption by 80–90% compared to "conventional" stoves.[3][4]

In contrast to conventional wood-burning stoves and fireplaces, in a rocket mass heater, combustion is close to complete. In a rocket mass heater, by-products of combustion, such as smoke, soot, and creosote compounds, are sucked into the insulated tunnel of the unit, where some claim they further combust, releasing even more heat energy to drive the rocket process, unlike a normal fire, where they are blown out the chimney.[5]