Small scale combined heat and power (CHP) is a topic of much research interest and has been identified by among others the UK Government as a key technology to reduce UK carbon emissions. Such systems are based around a combustion engine producing electric power, and where the waste heat from the engine is utilised for hot water and space heating. Some micro-CHP systems are available on the market, however market penetration is currently hindered by low electrical efficiency and high acquisition costs. For example, the Stirling engine based WhisperGen CHP unit manufactured by WhisperTech Ltd. produces electrical and thermal power outputs of 1kW and 7-12kW respectively, i.e. with an electrical efficiency of below 13%. Internal combustion engine based systems are offered by among others Honda and Baxi-SenerTec, and offer significantly better efficiencies (typically above 20%). However, IC engines suffer from noise, vibration, and high exhaust gas emissions, and are therefore by many considered unsuitable for domestic micro-CHP applications.

The Sustainable Power Research Group has developed an innovative concept for small- and micro-scale CHP systems based around the group's free-piston engine technology. The system is currently being tested in the laboratory and will provide a substantial improvement in electrical efficiency at small scale compared to existing commercially available systems. As the technology is subject to ongoing patent protection, no more technical details can be published at this stage.