In this paper a coupled model of microwave heating effect has been presented. The presented approach is based on coupled models reported already in literature. However, it allows handling problems where the oven cavity plays a role in heating, which is the case when combination ovens (ones including also heating elements installed) are considered or when imperfect isolation of the cavity walls results is increased cooling of a sample. Such models are rare in the literature, yet. The configuration of all surfaces of the cavity-sample system is accounted for through the surface-to-surface (S2S) radiation heat exchange model.