A new expression for the source term H, in the heat flow equation is developed for bipolar semiconductors. This term consists of heat generated by carrier-lattice collisions, recombination of electrons and holes, and other processes. The expression allows self-consistent calculations of self-heating in any device. The derivation is based on thermoelectric concepts. There exists several expressions for H in the general literature for calculating the temperature field, and the presently developed one is compared with the older ones. Discrepancies exist between all of the formulas and reasons for them are given. (C) 2014 Published by Elsevier Ltd.