Three energy system modelling tools were analysed as part of this study, each illustrating a different model type. How each were able to represent the energy system of Shetland and in particular the DSR enabled electric storage heaters was explored. The models compared are able to incorporate this technology using flexible demand or storage as a proxy however are unlikely to model this technology at the level of detail required if specifically considering the problem of DSR. The main challenges are the limitations in how they consider uncertainty of demand.