Tankless water heaters, as shown in Figure 1, are compact units that provide hotwater as needed, without storing it as traditional tank-type water heaters do. When a hot water tap is turned on, cold water enters the unit from the cold water supply.

Water heating is a heat transfer process that uses an energy source to heat waterabove its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. … Domestically, water is traditionally heated in vessels known as water heaters, kettles, cauldrons, pots, or coppers.