In the present work, the integration of a three-fluids heat exchanger in the evaporator of a reversible heat pump is evaluated. The heat exchanger includes internally finned passages for the refrigerant of the heat pump cycle and for the heat transfer fluid (water/glycol mixture) and externally finned passages for Phase Change Material (PCM). The selected PCM is a commercial paraffin (RT4) with nominal melting point of 4°C. The operation of the integrated heat pump with latent storage under typical cooling season conditions in Mediterranean warm climates were evaluated through an experimental campaign at CNR. The effect of operating modes and operational conditions was identified. During charge, the variable speed of the compressor was found to yield the maximum effect on storage dynamics, whereas during discharge the prevalent effect is that of the heat transfer fluid flow rate. Based on the outcomes of measurement, a critical design review and control strategy improvement were carried out.