Provided is a plant that includes: a boiler (30); a device connected to the boiler (30); a water supply source (41) that is configured to pool water; a water supply line (44) that supplies water from the water supply source (41) to the boiler (30); a cooler (50, 60g, 60s, 70g, 70s, 80) that transfers heat from a medium to be cooled to supply-water (W), which is the water flowing along the water supply line (44); a thermometer (59, 69, 79, 89) that determines a temperature of the medium to be cooled or the supply-water; and a temperature regulator (53, 62, 72, 82) that is configured to regulate the temperature of the medium to be cooled on the basis of the temperature determined by the thermometer (59, 69, 79, 89).