An operationally convenient methodology is presented for relating economic costs to entropy generation. This methodology, in the hands of the heat exchanger designer, allows an interaction with the system designer to gain insights into the trade-offs allowed between the thermodynamic irreversibilities of flow friction, heat transfer, heat leakage, and mixing. The methodology starts with a recognition of the appropriate individual irreversibilities, then relates the individual costs to system rating and energy penalties by thermodynamic arguments. The analysis loop is closed by considerations related to reduction of the individual irreversibilities in a cost-effective way. In contrast, the usual energy or “exergy” analysis provides an answer for the overall costs of the collective irreversibilities. This does not provide the engineer with the insight needed to minimize the individual irreversibilities in a cost-effective manner,