A hot water system (100, 200), wherein the system comprises: a hot water appliance comprising: a housing having a first water inlet port, a second water inlet port, and a water outlet port; a heat source disposed in the housing; a hydraulic assembly disposed in the housing and comprising a heat exchange line for allowing water passing therethrough to absorb heat generated by the heat source, a first pipe section connected with the first water inlet port and communicating with the heat exchange line, and a second pipe section connected with the second water inlet port and communicating with the heat exchange line; wherein the first pipe section and the second pipe section are arranged in parallel; a circulation pump disposed in the heat exchange line; a flow sensor disposed in the first pipe section; and an electrically actuated valve provided in the second pipe section; and the hot water appliance further comprises a controller electrically connected with the circulation pump, the flow sensor, and the electrically actuated valve; wherein the hot water system further comprises; a cold water line connected to the first water inlet port of the hot water appliance; a hot water line connected to the water outlet port of the hot water appliance; and a return water line having one end connected to the second water inlet port of the hot water appliance and the other end connected with the hot water line, characterized in that the circulation pump is capable of operating in a normal mode and a boost mode, and in that the controller is configured to control the electrically actuated valve to be closed to block the flow of water in the second pipe section and to activate the circulation pump to operate in the boost mode when the controller detects there is a flow of water in the first pipe section through the flow sensor. a hot water appliance comprising: a housing having a first water inlet port, a second water inlet port, and a water outlet port; a heat source disposed in the housing; a hydraulic assembly disposed in the housing and comprising a heat exchange line for allowing water passing therethrough to absorb heat generated by the heat source, a first pipe section connected with the first water inlet port and communicating with the heat exchange line, and a second pipe section connected with the second water inlet port and communicating with the heat exchange line; wherein the first pipe section and the second pipe section are arranged in parallel; a circulation pump disposed in the heat exchange line; a flow sensor disposed in the first pipe section; and an electrically actuated valve provided in the second pipe section; and the hot water appliance further comprises a controller electrically connected with the circulation pump, the flow sensor, and the electrically actuated valve; wherein the hot water system further comprises; a housing having a first water inlet port, a second water inlet port, and a water outlet port; a heat source disposed in the housing; a hydraulic assembly disposed in the housing and comprising a heat exchange line for allowing water passing therethrough to absorb heat generated by the heat source, a first pipe section connected with the first water inlet port and communicating with the heat exchange line, and a second pipe section connected with the second water inlet port and communicating with the heat exchange line; wherein the first pipe section and the second pipe section are arranged in parallel; a circulation pump disposed in the heat exchange line; a flow sensor disposed in the first pipe section; and an electrically actuated valve provided in the second pipe section; and the hot water appliance further comprises a controller electrically connected with the circulation pump, the flow sensor, and the electrically actuated valve; wherein the hot water system further comprises; a cold water line connected to the first water inlet port of the hot water appliance; a hot water line connected to the water outlet port of the hot water appliance; and a return water line having one end connected to the second water inlet port of the hot water appliance and the other end connected with the hot water line, characterized in that