Assessing grid-oriented flexibility of heat pumps in cold periods: Evidence from 761 residential heat pumps in Southern Germany

The electrification of the heating and transport sector is essential for achieving a carbon-neutral energy system. This increases electricity demand and places additional stress on low-voltage grids, necessitating grid reinforcement. However, the controlled use of flexible loads can mitigate peak demand and reduce the required grid expansion. To assess peak load on the low-voltage grid, it is essential to analyze heat pump electrical power consumption during the coldest periods. This study investigates the flexibility potential of residential heat pumps during the coldest periods of three to four consecutive days in recent years. Operational data from up to 761 air-to-water heat pumps installed in single-family houses in central Bavaria (Germany) are analyzed. The dataset, provided by iDM Energiesysteme GmbH, offers empirical insights from high-resolution measurements of real-world heat pump systems. The primary objective is to assess the potential for flexibilisation during the coldest periods of the year. The results indicate that, during both analyzed periods, the heat pumps offer a significant potential for flexibilisation. The compressors operate at a median load of around 30%, the systems are active for about 65% of the time, and the thermal load profile varies by about 60% between baseload and peak demand. Furthermore, the results show that time programs have a relevant impact on the load profiles. These findings demonstrate that, even on the coldest analyzed days, heat pump systems do not continuously operate at their technical limits, thus offering flexibility for grid-friendly load shifting.