Recent simulation-based studies have indicated that load shifting using Economic Model Predictive Control (E-MPC) of radiators for residential space heating can be utilized for demand response purposes in energy systems. However, there is a lack of studies on whether this load shift potential can be realized in real, inhabited buildings. This paper reports on a field experiment aiming at realizing load shifting of space heating in a single-family house with a hydronic radiator system connected to the local district heating. Radiators in a limited number of ‘active’ rooms were controlled using set-point schedules mimicking the typical behavior of E-MPC. The results indicate that it was possible to load shift heating consumption in the ‘active’ rooms but that the load shift for the building as a whole was limited due to the hydronics of the radiator system. The paper also reports on the several practical issues encountered during the experiments – issues that in different ways are barriers to the practical realization of demand response from E-MPC of hydronic space heating systems.