Storage Water Heaters

Storage heaters are the most common type of water heater in North America. Storage heaters work by heating water through electric heating elements or gas or oil burners and storing the heated water in its own tank. Thermostats control when the heating mechanism operates -- when stored water is below a set temperature, the storage heater activates; when a set upper limit for temperature is reached, the heater deactivates. While water is stored and not used, heat is very gradually lost. Most modern storage water heaters have very good insulation to minimize these standby heat losses.

Storage heaters can typically provide instant hot water volume from 2 gallons to 400 gallons. They are sized according to the peak demand of the user.

Storage heaters are preferred in luxury hotels and residences as their flow quality is much better than instantaneous or tankless water heaters. When a significant volume of hot water is required immediately, such as when used with bathtubs or rain showers with very high flow rates, an adequately sized storage heater will be able to keep up with the hot water demand, unlike standard instant water heaters.

Standby heat loss is a common consideration when considering the energy efficiency of a water heater. With the 2015 NAECA guidelines for storage heaters, even thicker insulation will be used to minimize heat losses. Heat traps and flue dampers are used to reduce unnecessary losses while timers and automated controls are used to lower stored temperatures during durations of unuse, further reducing heat losses. With the improved energy efficiency of A. O. Smith storage heaters, these heaters have comparable thermal efficiency compared to instant water heaters. For even better energy efficiency in storage heaters, a storage heater with built-in heat pump module is used.