Water heaters are gas, oil or electric-fired devices used to heat water for residential and commercial use. The most common types are storage water heaters and demand water heaters. Storage water heaters work by heating up water in an insulated tank can store water up to 20 to 80 gallons. Storage water heaters are fueled by electricity, natural gas, or oil.
A tankless water heater can save energy up to 50%. Some examples of a tankless water heater specification include an energy factor of .98, reduced wastage of electricity, and 98% efficiency for the life of heater.
A solar water heater use a glass tube that is coated with highly absorbing layer like aluminum nitrate that absorbs the heat energy of sun. A solar water heater can heat water to 60 °F and its storage capacity is 125 liters and more.
Water heaters are used in many applications. Examples include car washes, restaurants, and laundries. A tankless hot water heater is certified by Underwriters Laboratories, Inc. (UL). Federal regulations require that water heaters adhere to Energy Guide Labels which include Energy factor (EF) and First Hour Rating (FHR) that indicates the amount of water the heater will produce during peak hour usage.