This chapter has provided an introduction to micro-cogeneration technologies based upon fuel cells, internal combustion engines, and Stirling engines for the combined production of heat and electricity within buildings. These emerging technologies have the potential to deliver energy services more efficiently while reducing environmental impacts. However, due to the complex performance characteristics, these technologies can only be accurately assessed by building performance simulation programs that treat building thermal performance concurrently with electrical and HVAC systems.This chapter has outlined the recommended methods for modelling micro-cogeneration devices as well as techniques for calibrating these models to represent the performance of specific devices using measured data.