A model based on an additive mechanism of heat transfer is proposed for pool boiling of single component systems. The contributing modes of heat transfer are : (i) the heat transferred as latent heat to the evaporating microlayer, (ii) the heat transferred by transient conduction during re-formation of the thermal boundary layer and (iii) the heat transferred by turbulent natural convection from the heating surface not influenced by the bubbles. The heat flux due to the evaporating microlayer is estimated from the instantaneous microlayer thickness during the bubble growth period; An estimate of the nucleation site density is obtained from a literature correlation that includes the boiling surface characteristics. Experimental data from the literature and the present study show very good agreement with the model, validating the postulated mechanism;