A model was used to compute the performance of an ErNi‐based active magnetic regenerative refrigerator as a function of the hot and cold temperatures, applied magnetic field strength and mass flow rate. A device spanning 4 to 10 K with an applied field of 3 T and a mass flow rate of 1.3 g/s is predicted to have a cooling power of 2.8 W. Approximately 1 W of cooling is predicted with a magnetic field of 1 T. The device performance as a function of the mass flow rate is studied. The performance is not strongly dependent on the hot temperature but is very sensitive to changes in the cold temperature. This is attributed to the material properties of ErNi. Comparisons of the predicted performance of ErNi and three other magnetic refrigerants are also made. ©1996 American Institute of Physics.