Energy saving potential with smart thermostats in low-energy homes in cold climate

¹ Nearly Zero Energy Buildings Research Group, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
² Department of Civil Engineering, Rakentajanaukio 4 A, Aalto University, FI-02150 Espoo, Finland

^* Corresponding author: tuule.kull@taltech.ee

Abstract

Smart home systems with smart thermostats have been used for years. Although initially mostly installed for improving comfort, their energy saving potential has become a renowned topic. The main potential lies in temperature reduction during the times people are not home, which can be detected by positioning their phones. Even if the locating is precise, the maximum time people are away from home is short in comparison to the buildings’ time constants. The gaps are shortened by the smart thermostats, which start to heat up hours before occupancy to ensure comfort temperatures at arrival, and low losses through high insulation and heat-recovery ventilation in new buildings, which slow down the cool-down process additional to the thermal mass. Therefore, it is not clear how high the actual savings can be for smart thermostats in new buildings. In this work, a smart radiator valve was installed for a radiator in a test building. Temperature setback measurements were used to calibrate a simulation model in IDA ICE. A simulation analysis was carried out for estimating the energy saving potential in a cold climate for different usage profiles.