# Electrolysers

Equipment that uses electricity to split compounds: water into hydrogen, brine into chlorine, alumina into aluminium.

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

Conversion and use · Conversion devices · No. 103

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

The world can build 58 GW of electrolysers a year but made under 5 GW in 2025, leaving factories about 91% idle.

Chart: Illustration: Electrolysers

##### Where it comes from

Chart: Map of where it comes from

Direct current drives reactions uphill: water into hydrogen and oxygen, brine into chlorine, alumina into aluminium; Faraday's law sets the charge needed.

##### Three things to know

1. Chinese electrolysers installed in China cost USD 500 to 1,100 per kW in 2025, against USD 1,900 to 2,500 for those made elsewhere.
2. PEM electrolysers need iridium, of which only about 7.5 tonnes are mined a year; 1 GW needs about a tenth of that (calculated).
3. Aluminium smelters use 14.1 MWh per tonne, about 2.3 times the theoretical minimum (calculated).

##### The journey

1. 1 **Grid power**AC electricity, ideally cheap and clean
2. 2 **Rectifier**Converts it to DC for the stack
3. 3 **Stack**Current splits water, brine or alumina
4. 4 **Products**Hydrogen, chlorine, caustic soda, aluminium
5. 5 **Users**Refining, ammonia, methanol, steel, chemicals
 Covered in [The laws of energy: conservation, entropy and efficiencyEnergy](https://www.materialinsights.org/learn/energy/laws-of-energy/)[Storing energy: from fuel stocks to batteriesEnergy](https://www.materialinsights.org/learn/energy/storing-energy/)[Energy transitions and climateEnergy](https://www.materialinsights.org/learn/energy/energy-transitions-climate/)

##### Go deeper pick a tab to open it in full

## Other sections

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