Economiser circuits in liquid sodium service are very common in sodium cooled fast reactor systems. Large amount of cooling in the order of 100 °C–450 °C differential temperature is common for the auxiliary liquid sodium systems such as sodium purification and impurity monitoring. A sodium to sodium heat exchanger as economiser, sodium to air heat exchanger as heat sink and electrical heater for reheating are the process equipment generally used for the liquid sodium economiser circuits. Since the specific heat transfer area and manufacturing cost for economiser heat exchanger and sodium to air heat exchanger are largely different, optimised parameters for economiser circuits with conventional heat transport medium will not hold good for liquid sodium economiser systems. An optimisation study was performed for liquid sodium economiser circuit for arriving at an optimum design by considering the technical and economical aspects with optimum energy wastage.