The performance characteristics of a conventional thermoelectric generator operating under constant heat flux conditions have been computed. Expressions for power output, optimum efficiency, and optimum ratio of internal‐to‐load resistance show that optimization requires operating conditions appreciably different from those for the operation of thermoelectric generators having constant hot and cold junction temperatures. Performance curves are presented for the optimum ratio of internal‐to‐load resistance when either the internal resistance or the load resistance is under the control of the designer.