This paper describes four experiments which have been carried out to evaluate the speech output component of the INSPIRE spoken dialogue system, providing speech control for di.erent devices located in a smart home environment. The aim is to quantify the impact of different factors on the quality of the system, when addressed either in the home or from a remote location (office, car). Factors analyzed in the experiments include the characteristics of the machine agent during the interaction (voice, personality), the physical characteristics of the usage environment (acoustic user interface, background noise, electrical transmission path), as well as task-related characteristics (listening-only vs. interaction situation, parallel tasks). The results show a significant impact of agent and environmental factors, but not of task factors. Potential reasons for this .nding are discussed. They serve as a basis for design decisions which have been taken for the final system.