It is virtually envisioned that in the near future home-service robots will be assisting people in their daily lives. While a wide spectrum of utility of home-service robots has been proposed, i.e., cleaning, surveillance or go-and-fetch jobs, usability studies of the home-service robots have been less undertaken. This paper explores the usability issues, in particular, a map-based user interface for instructing home-service robots in the home environment. It focused on how the different map representation of the co-located environment would affect task performance of locating the home-service robots. The effectiveness of the map-based human-robot interface was thus analysed according to the dimensionality of the map, the location information of the elements in the co-located workspace. The experimental results showed that task performance was varied by the different map representation, providing a better understanding of what characteristics of the map representation were able to effectively support the human operator in instructing the home-service robots in the home environment.