Heusler alloys are widely studied due to their interesting structural and magnetic properties, like magnetic shape memory ability, coupled magneto-structural phase transitions and half-metallicity; ruled, for many cases, by the valence electrons number (N-v). The present work focuses on the magnetocaloric potentials of half-metals, exploring the effect of N-v on the magnetic entropy change, preserving half-metallicity. The test bench is the Si-rich side of the half-metallic series Fe2MnSi1-xGax. From the obtained experimental results it was possible to propose vertical bar Delta S vertical bar(max) = Delta H-0.8 (alpha + beta N-v), i.e., the maximum magnetic entropy change depends in a linear fashion on N-v, weighted by a power law on the magnetic field change Delta H (alpha and beta are constants experimentally determined). This phenomenological model opens doors for further theoretical investigations. In addition, it was also possible to predict a new multifunctional Heusler alloy, with enhanced magnetocaloric effect, Curie temperature close to 300 K and half-metallicity. (C) 2016 Elsevier B.V. All rights reserved.