We present a non-equilibrium Preisach-type hysteresis model based on the first order magnetocaloric material Gd5Si2Ge2. The model is developed from isofield magnetization measurements and first order reversal curves, both of which constitute a new and detailed approach to characterizing and modelling magnetocaloric materials. It is shown that the model reproduces the magnetization data, directly measured adiabatic temperature changes and provides a good description of the material behavior under application conditions. We find that the material settles in an area of metastability under continuous magnetization cycles, which effectively limits the adiabatic temperature change by the amount of thermal hysteresis present. We suggest a straightforward method for realistic estimation of the magnetocaloric effect from indirect measurements.