Hot water supply apparatus and control method for hot water supply apparatus

A hot water supply apparatus, comprising:

• a heat pump unit that operates with electrical energy as a driving source;
• a hot water storage tank that stores hot water heated by the heat pump unit;
• a hot water supply circuit that supplies hot water from the hot water storage tank;
• an auxiliary heat source device for burning fuel and heating hot water to be supplied in response to a stored hot water heat amount of the hot water storage tank being insufficient for a heat amount used for hot water supply;
• and
• a control device that controls the heat pump unit and the auxiliary heat source device,
• wherein the control device
• calculates a predicted heat amount used for hot water supply for each unit time period based on a past usage record of hot water supply,
• estimates an error distribution of an actual heat amount used for hot water supply with respect to the predicted heat amount used for hot water supply,
• calculates an expected value of loss in a target index, caused by a hot water storage operation of the heat pump unit and a combustion operation of the auxiliary heat source device in response to generating the actual heat amount used for hot water supply, using the estimated error distribution, and
• obtains an optimal stored hot water heat amount that minimizes the expected value of loss, and controls the heat pump unit so that the hot water storage tank stores the optimal stored hot water heat amount.