At present magnetic refrigeration shows a realistic potential to penetrate into some niche markets in the field of cold and hot “production”. It is well known that a refrigerator for cooling and a heat pump for heating are machines based on the same principle. A small review on magnetic heat pump studies is outlined and a simple engineering calculation scheme to determine the coefficient of performance for a magnetic heat pump with a rotary porous structure heat exchanger is presented. Magnetic heat flux line distributions are calculated by a 2‐d finite element method numerical simulation program with the objective to obtain high field's μ0H with not too heavy permanent magnets assemblies. The porous structures are geometrically optimised to obtain maximal magnetic field inductions. It is shown that for a water/ethylene‐glycol magnetic heat pump the coefficient of performance is higher than that of a conventional heat pump. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)