Customary evaporator or condenser characterisation provides data concerning the circulating mass flow rate and inlet and outlet conditions for each fluid flow. This paper analyses the estimation, from those typical experimental results, of the average heat transfer coefficient (HTC) taking place during the phase change region and its corresponding uncertainty. This analysis shows the influence of the typical measurement uncertainties of different measured magnitudes (temperatures, pressures and mass flow rates) and of operating conditions on the total uncertainty in the estimation of the two-phase HTC (2PhHTC). Additionally, the influence of the choice of heat exchanged, by the refrigerant or by the water, on the estimation of the 2PhHTC is also considered. The study is applied to a brazed plate heat exchanger (BPHE) working as an evaporator at both basic flow arrangements: co-current and counter-current. The results clearly show that the operating conditions in which this kind of equipment is typically characterised (and used) makes the estimation of the 2PhHTC difficult. The influence of the model used for the data reduction is also discussed. Finally, a sample of values of the 2PhHTC obtained from the analysis of the characterisation campaign results of a BPHE evaporator working with R22 is presented and briefly discussed.