Cogeneration, commonly called combined heat and power (CHP), is the simultaneous production of electricity and useful heat from a single energy source. Instead of letting heat generated during electricity production escape unused, CHP captures that thermal energy and puts it to work for space heating, industrial processes, or other thermal needs. Systems built around a heat engine or a power station can be configured for local use in a factory, for a cluster of buildings, or for wider district heating networks.

How cogeneration works

In a typical CHP installation, a prime mover such as a gas turbine, reciprocating engine, microturbine, or fuel cell generates electricity. Instead of discarding the exhaust heat to the atmosphere through cooling towers or flue gases, the system diverts thermal energy into heat exchangers and distribution systems. This recovered heat serves domestic or industrial heating, process steam, or other thermal demands. Where cooling is required, moderate-temperature waste heat (roughly the order of 100–180°C) can drive absorption chillers to produce chilled water for air conditioning, a practice sometimes called trigeneration or polygeneration.

Common configurations and components

  • Gas- or diesel-engine CHP units coupled to heat recovery boilers for hot water or steam.
  • Combined-cycle plants that harness turbine exhaust for a steam cycle and district heating connections.
  • Small-scale, building-mounted CHP for hospitals, campuses, or industrial sites that need consistent heat and power.

CHP systems may be integrated on-site or connected into a local thermal network (district heating). Such networks are especially developed in parts of Scandinavia and eastern Europe, where heat distribution infrastructure complements centralized electricity and heat production.

History and development

The concept of capturing and reusing waste heat is longstanding: many early urban power plants provided both power and steam or hot water to nearby customers. Over time, advances in turbomachinery, control systems, and regulatory frameworks revived interest in CHP as a way to improve overall resource use. Modern installations emphasize fuel-to-output efficiency and emissions control, and can be driven by fossil fuels, biomass, biogas, or by integrating renewable technologies.

Benefits, limits, and notable facts

Cogeneration is widely regarded as a more efficient and resource-conscious way to use fuel than producing electricity and heat separately. Conventional power plants let much of the input energy escape as waste heat, but CHP captures this energy so it can perform useful work. From a thermodynamic perspective, the process makes better use of fuel enthalpy and can reduce greenhouse-gas emissions per unit of useful energy. However, the feasibility of CHP depends on local heat demand, economics, and regulatory factors. Some installations are described as regeneration or as part of broader polygeneration schemes that provide electricity, heating, and cooling from the same source.

Applications and distinctions

CHP is used in a wide range of settings: industrial plants that require steam, hospitals and universities with continuous heating needs, municipal district heating systems, and commercial buildings seeking energy resilience. Compared with separate generation, CHP can increase primary energy utilization substantially and offers advantages for distributed energy generation and grid support. The approach is connected to broader discussions about energy systems and sustainability; see materials on energy for context and on the thermodynamically informed principles that underlie component design and performance.

For readers wanting technical or policy details, resources on plant types, environmental permitting, and economic assessment provide practical guidance. Additional technical materials explore absorption chilling, micro-CHP units for individual homes, and integration with renewable fuels and energy storage to further improve system flexibility and emissions performance.

Related topics and further reading: heat engines, power stations, electricity, useful heat, conventional power plants, cooling towers, domestic or industrial heating, Scandinavia, eastern Europe, regeneration, thermodynamically, efficient, fuel, waste heat, useful work, energy.