An investigation under which conditions industrial waste heat utilised with magnetic energy conversion machines can be a possible alternative to conventional energy conversion technologies is presented. The application of a numerical model leads to the thermodynamic efficiency, the exergy efficiency, and approximate values of the total mass and the total volume of a magnetic energy conversion machine. The exergy efficiency depends strongly on the magnetic field strength. A high frequency of operation reduces the mass and volume of a device. Magnetic energy conversion may beat conventional technologies, especially if large low-exergy heat sources are at ones disposal.