At the LENI a heat pump model has been developed, which aims to simulate a single state compression heat pump in both steady state and transient regime. For gaining the experimental data and for the simulation the same set of input data is used. The goal is to approximate the output values of the model ym to the ones measured in the experiments. Therefore a certain number of parameters need to be defined in order of obtaining the highest accuracy possible. At the beginning these different parameters γ need to be found and a criterion needs to be appointed which can be used to judge the accuracy of the model. The first approach to the identification is to only work with the steady states. This includes to select steady values out of a data sheet and to change the model so that only steady states are computed. As soon as the model is successfully running for the steady states an optimizer needs to be chosen to finally output the best values of parameters. Subsequently the improvement of the output vector ym needs to be checked. As during the examination some computational problems have been revealed, which interfered with the optimization, various influences on the heat pump model were investigated. It was tried to find the reason for numerical problems and to eliminate those in order to finally be able to optimise the parameters. To identify the model in the transient regime the model needs to be linearised at a typical operation condition. The new chosen criterion must also take into account the transient regimes and the optimality of the solution has to be proved. The numerical problems which exist for the steady state also influence the transient regime. As the emphasis was therefore put on finding the origin of the instabilities, the identification of the transient regime was only briefly worked on.