The compressor operates without a backup electric heater down to an ambient temperature of −28 °C and can be integrated with existing radiators with a high water flow temperature of up to 75 °C at an outdoor temperature of −15 °C. It is capable of supplying hot water at 55 °C even at an outdoor temperature of −28 °C. Sterilisation process without an electric heater. It can also achieve domestic hot water temperatures of up to 65 °C without using an electric heater, allowing tank sterilisation to be carried out during heat pump operation.