What Is CHP?

CHP 101

Combined heat and power (CHP), also known as cogeneration, is a technology that uses a single fuel source to generate both heat and electricity. CHP systems generate electricity and capture the heat that would otherwise be wasted to provide useful thermal energy, such as steam or hot water, that can be used for space heating, cooling, domestic hot water, and industrial processes.

CHP systems can be located at an individual facility or building, or can be a utility resource or part of a district energy system. CHP systems are typically located at facilities where both electricity and thermal energy are needed. CHP is used in over 4,400 facilities across the U.S.

CHP and Efficiency

CHP systems are efficient electric and thermal energy generation units. Improvements in CHP technology over time have resulted in properly designed CHP systems typically operating with an overall efficiency of 65% to 85%, with some approaching 90%. This is compared to an overall efficiency of only 45% to 55% when electricity and thermal energy are provided separately. CHP systems achieve these high efficiencies by recovering the waste heat byproduct of electricity generation as useful thermal energy for heating and cooling.

Because they operate efficiently, CHP systems combust less fuel to provide the same energy services. This efficient generation of energy reduces all types of emissions, including greenhouse gasses (GHGs) such as carbon, criteria pollutants, and hazardous air pollutants.

CHP and Renewables

As a distributed resource serving both electric and thermal loads at the point of production, CHP can also help support intermittent renewable resources by reducing load on the regional grid and providing a baseload source of power to serve electric demand even when intermittent renewable resources are not generating power. CHP can complement renewable resources such as solar and wind and allow facilities to utilize these intermittent renewable resources while maintaining reliability.

Historically, CHP units have run on traditional fuels, and many today use natural gas. This use of CHP can be thought of as “CHP 1.0,” the first wave of CHP technologies that relied on fossil fuels. However, CHP units can be fueled by renewable and lower-carbon fuels such as biogas, RNG or biomethane, and hydrogen, or “CHP 2.0.” Use of these lower-carbon fuels can allow CHP systems to reduce emissions even further than they do under CHP 1.0.

CHP and Microgrids

CHP systems can provide reliable power to a local community as part of a microgrid, allowing several buildings or facilities to keep the lights on during a grid outage. Over 200 microgrids in the U.S. use CHP, equivalent to 35% of all the nation’s microgrids. Moreover, CHP is used in 67% of those microgrids that operate continuously.

Microgrids are used by universities, military installations, municipalities, and public institutions, helping maintain the reliability of their electric and thermal energy supply and to improve their resilience against extreme weather and power outages.

CHP and Resiliency

CHP is a distributed energy resource that is highly resilient to a variety of weather events. Natural gas fueled CHP is less likely to experience impacts from a variety of disasters than other types of distributed generation. During a grid outage, CHP systems can function in “island mode,” automatically separating a host facility or microgrid from the utility grid and providing consistent power and thermal energy to the facility or facilities connected to the microgrid.

Gas infrastructure is less likely to be impacted by severe weather events than other infrastructure systems, as gas pipelines are predominantly underground and the system can continue to operate at high pressure with only half of the compression stations functioning. In the future, this infrastructure may be used to transport higher volumes of lower-carbon fuels. In addition, CHP systems that use fuels obtained on-site, such as biogas from a landfill or wastewater treatment plant, may be less reliant on gas infrastructure to maintain operations, adding another layer of resiliency.

Learn More about CHP

Review the materials in the Resources page to learn more about CHP.

Watch this short illustrated video prepared by The Pew Charitable Trusts: