The combined generation of heat and power at household level (micro-CHP) has the potential to become an important element of a future, sustainable energy system. Currently, different prototypes are being developed, some of them based on renewable energies. A Stirling engine to be integrated in pellets heating systems developed by the Styrian company SPM (Stirling Power Modules Energy Conversion) is one such example. Households equipped with such a CHP-system become generators of green electricity. While much emphasis is put on technological developments there is still a deficit of knowledge and research into users and usage patterns of micro-CHP. As a matter of fact, there are different scenarios conceivable, of how micro-CHP might be used in households. End-users could put special emphasis on autarky, they might try to maximise their revenue by delivering green electricity to the grid, or they could collectively link together into virtual utilities. Similarly the position of important stakeholders and actors in the energy system is widely an open question. It is thus the aim of this project to deal with these open questions of a user-friendly design and market introduction of CHP-systems and assess potential impacts on the energy system. Qualitative interviews and quantitative social surveys concentrate on two groups who might be most interesting as early users: current users of pellet heating systems and households owning of photovoltaic facilities already generating electricity for the grid.