Already popular for more than a century in industry, Combined Heat and Power (CHP) production is now penetrating domestic markets. The greatest potential for domestic CHPs (dCHPs) is in the replacement of boilers in dwellings, small communities (a group of houses or apartments), and micro-enterprises. The system is attractive to both the consumer (saving on total energy cost) and the utility company (creating opportunities for customer retention and peak-load reduction). The first dCHPs, using an internal combustion engine, have been on the market for approximately six years and have proven their reliability. Newer systems tend to use Stirling engines, which run quieter, making them more suitable for use in the domestic environment. These systems however have high heat-to-electricity ratios, which introduce difficulties in homes, where demand for electricity increases and heat demand is reduced.
In the near future this may be addressed by dCHPs using hydrogen fuel cells that generate one kWh of electricity for each kWh of heat. These systems are expected to be commercially available around 2010. However the question of whether dCHP systems will see a real breakthrough also depends on the evolution of competing technologies such as high efficiency boilers, heat pumps, and solar heating systems.