# Combined heat and power

Making electricity and useful heat (and cooling) from the same fuel.

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

Recovery and reuse · Heat to power and cogeneration · No. 128

- Recovery and reuse
- Heat grade: All grades
 Recovery and reuse · Heat to power and cogeneration · Foundation · Energy

Make electricity and keep the engine's heat, and up to 82% of the fuel does useful work instead of 50-55%.

Chart: Illustration: Combined heat and power

##### Where it comes from

Chart: Map of where it comes from

A gas engine or turbine makes power, and its hot exhaust and cooling water are captured for steam, hot water or cooling. Packaged units range from 24 kW to 7.5 MW.

##### Three things to know

1. Hot water at 82 C is worth only about 13% of its energy as work, so CHP's real exergy efficiency is about 35-46%.
2. An absorption chiller turns waste heat into cooling: double-effect units deliver 1.35-1.42 units of cold per unit of heat.
3. Gas CHP emits about 0.21-0.24 t CO2 per MWh after credits, against above 0.64 t for the US marginal grid.

##### The journey

1. 1 **Fuel**Natural gas, biogas or liquid fuel
2. 2 **Engine or turbine**Generates electricity for the site
3. 3 **Heat recovery**Exhaust and jacket water captured
4. 4 **Heat or cooling**Steam, hot water, or absorption chilling
5. 5 **Site users**Hospitals, factories, campuses and homes
 Covered in [The laws of energy: conservation, entropy and efficiencyEnergy](https://www.materialinsights.org/learn/energy/laws-of-energy/)[Making electricity: thermal, nuclear, hydro, wind and solarEnergy](https://www.materialinsights.org/learn/energy/making-electricity/)[Moving energy: wires, pipes and shipsEnergy](https://www.materialinsights.org/learn/energy/moving-energy/)[Efficiency, waste heat and recoveryEnergy](https://www.materialinsights.org/learn/energy/efficiency-and-recovery/)

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

## Other sections

- [Overview](https://www.materialinsights.org/energy/e_chp/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_chp/correlation/index.md)
- [Science and thermodynamics](https://www.materialinsights.org/energy/e_chp/rc-sci/index.md)
- [Engineering and integration](https://www.materialinsights.org/energy/e_chp/rc-eng/index.md)
- [Economics and contracts](https://www.materialinsights.org/energy/e_chp/rc-econ/index.md)
- [Impact and additionality](https://www.materialinsights.org/energy/e_chp/rc-impact/index.md)
- [What to track](https://www.materialinsights.org/energy/e_chp/tracking/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_chp/links/index.md)