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combined heat and power

Combined heat and power (CHP) is the generation of both electricity and useable heat at the same time. It is also known as cogeneration. When some of the generated heat is used in adsorption/absorption chillers for cooling, it is known as tri-generation.

Benefits of CHP

The key benefits of using CHP systems are energy efficiency (and the associated carbon savings) and energy security.

In conventional power stations, both electricity and heat are generated. However, the heat is simply wasted, it is only the electricity that is seen as a useful product. This has a substantial impact on the efficiency of the system as so much of the energy in the fuel consumed is simply lost. For example, in the UK, the efficiencies of gas power stations are around 50%, coal-fired stations have even lower efficiencies, around 38%. In contrast, in CHP systems, rather than being wasted, the heat is captured for use. In this way, efficiencies of up to 80% can be reached. 

CHP systems are also available at a wide range of scales and so are particularly suited to local use. This produces further efficiency benefits as transmission losses are reduced.

Compared to conventional power generation with its associated heat losses, carbon savings of up to 30% can be made using CHP with the same fuel source simply due to the increased system efficiency.

Comparing CHP systems with different fuel sources, renewables based CHP systems in particular can offer substantial carbon savings.
Carbon savings are also often associated with a reduction in other pollutants as less fuel overall is being used to produce the same amount of useful energy.

Energy security can be also be enhanced by CHP systems through more efficient fuel use (less overall fuel is needed) and diversification of energy supply.

In recognition of the benefits of CHP, there are several Government financial incentive schemes as well as Government policies to encourage the use of CHP. 

The financial incentive schemes vary with the scale and CHP technology. For renewable fuel systems examples include the Renewables Obligation (RO) which gives tradeable certificates for the electricity generated, the Renewable Heat Incentive (RHI) which provides payments for 20 years on the heat generated and the Feed in tariff (FiT) which provides payments for 20 years on the electricity generated. 

For more details of the renewable incentive schemes, please visit our RHI and ROCs page.

Good quality renewable and non-renewable CHP systems are also eligible for Enhanced Capital Allowances although these cannot be claimed in conjunction with the RHI.

Increasing recognition of the benefits of District Heat Networks (DHN) has also led to incentive schemes that benefit CHP systems indirectly as they are so suited to DHN use. For example, the Scottish Government’s District Heating Loan Fund.

CHP applications

CHP systems are particularly suited to sites where there is a consistent need for both low-grade heat (<100 C) and electricity. Many systems are sized to meet the heat needs on site and connected to the low voltage electrical distribution system so any excess electricity can be exported to the grid.

At the end of 2015, the installed CHP capacity in the UK stood at 5,692 MW of electrical output from 2102 installations. Of these installations, 383 schemes (85% of electrical capacity) are in the industrial sector and 1,719 schemes (15% of capacity) are in the agricultural, commercial, public administration, residential and transport sectors (figures from the DECC, Digest of UK Energy Statistics).


Harpers CHP, Unit 2, North Road Industrial Estate, INSCH, Aberdeenshire, AB52 6XP

Email: | Phone: (01464) 821822