Based on the cycle model of a class of irreversible threeheatsource heat pumps, the heating load per unit cost is taken as the thermoeconomic objective function, which is used to investigate the influence of the investment cost, supplyingheat cost, other charge cost, and several main irreversibilities on the performance of the cycle. The maximum objective function and the corresponding performance parameters are calculated. The optimally operating regions of the heat pump and the bounds of important per...