# Boilers, furnaces and stoves

Burning fuel for heat: industrial boilers, kilns, furnaces, gas and biomass stoves.

Source page: https://www.materialinsights.org/energy/e_combustion_heat/

Conversion and use · Conversion devices · No. 107

- Conversion and use
 Conversion and use · Conversion devices · Foundation · Energy

Burning fuel for heat is about 41% of all energy humanity uses, from 100 MW boilers to three stones under a pot.

Chart: Illustration: Boilers, furnaces and stoves

##### Where it comes from

Burning joins the carbon and hydrogen in fuel with oxygen, and the hot gas hands its heat to water, metal or a cooking pot. Heat was almost half of world final energy in 2024.

Boilers come from a mix of global groups and national specialists; Vaillant calls itself the world leader in central heating units. In Africa, LPG serves more than 70% of people with clean cooking.

##### Three things to know

1. A 95% efficient boiler making 60 C water keeps only about 14% of the fuel's ability to do work, because a flame is far hotter than needed.
2. Open fires and the simplest stoves deliver under 10% of their heat to the pot, while good LPG stoves manage about 42 to 70%.
3. In the US, 36% of the energy used for process heating is lost through flues, pipes, steam traps and walls (2010 data).

##### The journey

1. 1 **Fuel**Gas, oil, coal, LPG or wood
2. 2 **Flame**Burner releases chemical energy as hot gas
3. 3 **Heat exchange**Tubes or chamber pass heat to water
4. 4 **Steam or product**Steam, hot water, molten metal, clinker
5. 5 **End use**Drying, melting, cooking and heating homes
 Covered in [Muscles, wood, water and wind: energy before fossil fuelsEnergy](https://www.materialinsights.org/learn/energy/energy-before-fossil-fuels/)[Energy transitions and climateEnergy](https://www.materialinsights.org/learn/energy/energy-transitions-climate/)

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## Other sections

- [Overview](https://www.materialinsights.org/energy/e_combustion_heat/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_combustion_heat/correlation/index.md)
- [Science and limits](https://www.materialinsights.org/energy/e_combustion_heat/science/index.md)
- [Value chain](https://www.materialinsights.org/energy/e_combustion_heat/valuechain/index.md)
- [Unit economics](https://www.materialinsights.org/energy/e_combustion_heat/economics/index.md)
- [Engineering methods](https://www.materialinsights.org/energy/e_combustion_heat/methods/index.md)
- [Equipment and suppliers](https://www.materialinsights.org/energy/e_combustion_heat/equipment/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_combustion_heat/links/index.md)