A refrigeration cycle system (100, 200, 300) comprising: a refrigerant circuit (10, 210, 310) adapted to circulate a refrigerant, the refrigerant circuit comprising a compressor (15, 25), a heat-source-side heat exchanger (17, 27), an expansion valve (18, 28, 46, 56, 66), and a usage-side heat exchanger (45, 55, 65); a plurality of actuators (19m, 29m, 47m, 57m, 67m) configured to perform a refrigeration cycle in the refrigerant circuit; a storage unit (1b, 2b, 42, 52, 62) configured to store in correlation with the actuators respectively at least any of a relational expression showing the relationship between the amount of energy inputted to the actuators, and a refrigerant target state quantity of refrigerant flowing through the refrigerant circuit, the quantity being any of a temperature control target value, a pressure control target value, or a physical-quantity control target value equivalent thereto, first information for creating the relational expression, and second information for attaining the relational expression using values inputted to the actuators and values that indicate states of the actuators corresponding to the input values; refrigerant state quantity acquisition means (12, 13, 14, 22, 23, 24, 44, 54, 64) configured to acquire the current refrigerant state quantity that corresponds to the value of the refrigerant target state quantity; and a control unit (7, 207, 307), characterized by the control unit being configured to obtain the sum of the energy inputted to the actuators, or the sum of the amount of change in the energy inputted to the actuators, on the basis of the relational expression for the postulated case that a change has been made from the current refrigerant state quantity, and configured to, while updating the value of the refrigerant target state quantity so that the sum of energy inputted to the actuators is less than the current level or so that the sum of the amount of change in the energy inputted to the actuators is a low value, control at least one of the actuators so that the value acquired by the refrigerant state quantity acquisition means approximates the updated value of the refrigerant target state quantity. a refrigerant circuit (10, 210, 310) adapted to circulate a refrigerant, the refrigerant circuit comprising a compressor (15, 25), a heat-source-side heat exchanger (17, 27), an expansion valve (18, 28, 46, 56, 66), and a usage-side heat exchanger (45, 55, 65); a plurality of actuators (19m, 29m, 47m, 57m, 67m) configured to perform a refrigeration cycle in the refrigerant circuit; a storage unit (1b, 2b, 42, 52, 62) configured to store in correlation with the actuators respectively at least any of a relational expression showing the relationship between the amount of energy inputted to the actuators, and a refrigerant target state quantity of refrigerant flowing through the refrigerant circuit, the quantity being any of a temperature control target value, a pressure control target value, or a physical-quantity control target value equivalent thereto, first information for creating the relational expression, and second information for attaining the relational expression using values inputted to the actuators and values that indicate states of the actuators corresponding to the input values; refrigerant state quantity acquisition means (12, 13, 14, 22, 23, 24, 44, 54, 64) configured to acquire the current refrigerant state quantity that corresponds to the value of the refrigerant target state quantity; and a control unit (7, 207, 307), characterized by the control unit being configured to obtain the sum of the energy inputted to the actuators, or the sum of the amount of change in the energy inputted to the actuators, on the basis of the relational expression for the postulated case that a change has been made from the current refrigerant state quantity, and configured to, while updating the value of the refrigerant target state quantity so that the sum of energy inputted to the actuators is less than the current level or so that the sum of the amount of change in the energy inputted to the actuators is a low value, control at least one of the actuators so that the value acquired by the refrigerant state quantity acquisition means approximates the updated value of the refrigerant target state quantity.