Solar collectors and photovoltaic panels are devices widely used for heating water for both heating and domestic purposes. Due to the variable nature of solar radiation, it is advisable to include in solar energy-based systems thermal storages that accumulate energy at times of overproduction and discharge it at times of demand. In this paper, we present the results of simulation research to compare the possibility of two different charging systems for a 24000 m3 seasonal pit thermal energy storage (PTES). The first uses electricity generated by photovoltaic panels and converted to heat in an electrode boiler to charge the heat store. The second is utilising a solar collector for this purpose. Based on the simulation calculations carried out in TRNSYS 18, it can be concluded that, from an investment perspective, a system based on solar collectors is more cost-effective. In addition, the installation takes up less space compared to a photovoltaic panel farm.