Traditional water heaters, also known as tank water heaters, store a large volume of hot water in a tank. They typically use gas or electricity to heat the water, which is then kept at a set temperature until needed. When you turn on a hot water tap, hot water is drawn from the top of the tank, while cold water enters the bottom to be heated. These heaters come in various sizes, usually ranging from 20 to 80 gallons, to accommodate different household needs. While they are generally less expensive to install than other types, they can consume more energy over time due to standby heat loss, where heat escapes from the tank.