Combined heat and power (CHP) is a technology which can provide a building with both heating and electricity, generated in a single process, with a typical ratio of about 2:1. Domestic installations are usually powered by mains gas or LPG, although larger commercial units can run on a variety of fuels.

Unlike conventional electrical generation – where coal and gas-fired power stations have to vent huge amounts of unused heat into the atmosphere – CHP captures a much higher proportion of the heat produced, which ensures much greater efficiency. In addition, the relative efficiency of the process is higher as the electricity is generated on-site, which means that losses incurred through the transmission and distribution network can be avoided.

Firstly, we’ll look at the benefits of CHP:

• Produces electricity for use within the building.
• Can produce significant reductions in running costs and carbon dioxide emissions if sized correctly.

There is however one limitation that should be taken into account:

• CHP units operate most efficiently when running for long periods, generally for more than 18 hours a day. Large hot water demand, and large enough thermal stores to store the generated hot water, are required.

In addition, there are some other considerations that should be borne in mind:

• The Feed-In Tariffs scheme closed at the end of March 2019, and therefore this needs to be considered when reviewing running costs and payback periods.
• An incorrectly sized CHP unit may cost more money to operate than conventional solutions.
• There is a significant step in capital cost once CHP units with a larger thermal output than 17 kW are considered, so correct sizing is essential.
• Micro CHP boilers are not suitable for small well-insulated dwellings, as there isn’t sufficient heat demand to operate efficiently.
• The continuing decarbonisation of the electricity network does means that CHP could have higher carbon dioxide emissions than other options.

If you’d like to find out more about combined heat and power units, and their suitability for a particular project, please contact us.