In this paper we present a non-linear state space model for a saucepan-induction hob system, based on the application of the fundamental thermal equations. We divide the whole system in subsystems and we choose as state variables the temperatures of the subsystem, which are able to increase or decrease its internal energy. Through this, we get a solution to study the heat fluxes and the energy losses, taking into account the material and the geometry of the elements. Besides, we consider the fact that in industry the most extended controllers are linear and we get the linear approximation of our model. Both, linear and non-linear models, are compared with real data from a test. Although often this is enough, we evaluate the possibility of using a simpler model and we apply a systematic technique to reduce the model order, without calibrating its parameters again.