The rising share of fluctuating renewables in our energy system requires measures to stabilize overstressed energy grids. A focus of energy research is on affordable and available storages that can absorb excess energy and store it. For instance, the existing building mass is partially already coupled to the power grid via heat pumps or air conditioning systems. If the controller and the energy management system work efficiently using forecasts and other (easily) obtainable information, those technologies can shift load peaks to hours, when the electricity price is low and benefits for the grids are high. The thermal capacity of the buildings guarantees the thermal comfort between the operating times of the HVAC systems. However, the controller and the management system strongly depend on the underlying thermal model of the building and its parameters. Therefore, we focus on practicable and easily identifiable grey box models that do not depend on the exact knowledge of the building materials. This approach ensures transferability to other buildings and produces sufficient results for future control concepts. Finally, we present first measurement data and results of the system parameter identification.