Within the scope of this work the energy saving potential of self-ventilated IEC standard induction motors by means of load dependent fan decoupling has been investigated. The decoupling is mainly evaluated with respect to periodical partial load operation and low ambient temperature. For this purpose, standard machines between 0.75kW and 5.5kW have been measured in terms of efficiency and thermal behaviour. Furthermore, thermal models of the machine where established and used for simulation steps. The work shows, that only marginal energy savings can be reached, if at all. IE3 induction machines show great sensitivity to temperature changes in terms of their efficiency, such that the already relatively small efficiency gain via the saved fan losses are overcompensated for most of the machines and for most lifelike use-cases. As a best-case scenario, a 5.5kW machine in periodical short-time duty (S6) has reached an annual potential of 1.2‰ energy savings, yielding roughly four Swiss Francs of cost savings. Thus, a mechanical decoupling has to be seen sceptical with regard to economics such that the authors advise to not further investigate this project.