Provided is a plant that includes: a boiler; a device connected to the boiler; a water supply source that is configured to pool water; a water supply line that supplies water from the water supply source to the boiler; a cooler that transfers heat from a medium to be cooled to supply-water, which is the water flowing along the water supply line; a thermometer that determines a temperature of the medium to be cooled or the supply-water; and a temperature regulator that is configured to regulate the temperature of the medium to be cooled on the basis of the temperature determined by the thermometer.