Although there have been a number of fuel cell micro CHP systems installed in Europe, together with around two thousand, mainly PEM fuel cell systems, in Japanese homes, fuel cells cannot be described as "commercially available".  The European systems have all been installed as technology trials, whilst the Japanese products have each been subsidised by the Japanese government with grants of up to £30,000 per installation.

However, these installations have served to demonstrate the performance of fuel cell technology, leaving two major obstacles to commercialisation, namely cost and service life.  Unlike engine based technologies, fuel cells' life is characterised by continuous degradation of performance rather than catastrophic failure and economic viability may be determined by average rather than initial performance.

The two main types of fuel cells being developed for micro CHP applications are PEM (Proton Exchange Membrane) and SOFC (Solid Oxide Fuel Cells).  The former are also being developed for automotive applications and historically formed the majority of systems.  However, SOFC units have the advantage of reforming Natural Gas into Hydrogen without the need for a separate reforming process, reducing the cost and complexity of the unit and raising conversion efficiency; balanced against this is the very high operating temperature of such fuel cells and their need for continuous heat output (even when there is no thermal demand).  Although this feature does raise some challenges, it has recently become apparent that the relatively low operating temperatures of PEM fuel cells impose limitations in domestic CHP applications with respect to the provision of hot water at a high enough temperature.  This, combined with the higher potential electrical efficiency of SOFC units, seems to favour SOFC in domestic CHP applications.

For further discussion of the relative merits of fuel cell types see section on papers, or click on links below for details of PEM and SOFC micro CHP products.