The heat pump double cylinder WP-DF combines two buffer cylinders: the upper one is used to heat water via a fresh water station, which enables a high hot water output even at low flow temperatures. A layer separating plate prevents mixing so that the upper hot zone remains stable. The lower, hydraulically separated cylinder can be operated with low flow temperatures and serves as a hydraulic separator for heating and cooling circuits. Both cylinders have connections for electric heating elements. The high-quality PU rigid foam insulation reduces energy losses and increases efficiency.