Water heating is a thermodynamic method using a power source to heat water beyond its initial temperature. Typical domestic uses of hot water are for cooking, cleaning, bathing, and space heating. In industry, both hot water and water heated to condensation have many uses.
Domestically, water is usually heated in vessels known as water heaters, kettles, cauldrons, pots, or coppers. These metal vessels heat a batch of water, but do not produce a continual supply of heated water at a preset temperature. The temperature will vary based on the consumption rate of hot water; the water becomes cooler as flow is increased.
Appliances for providing a more-or-less stable supply of hot water are variously known as water heaters, hot water heaters, hot water tanks, boilers, heat exchangers, calorifiers, or geysers depending on whether they are heating filtered or non-potable water, in domestic or industrial use, their energy source, and in which part of the world they are found. In domestic installations, potable water heated for uses other than space heating is sometimes known as domestic hot water (DHW).