A hybrid water heater is a combination of a tank-style water heater and a tankless water heater. It uses the advantages of each system to overcome the disadvantages of the other. A hybrid water heater supplies hot water in a volume comparable to tank-style water heaters, but it is almost as energy efficient as a tankless water heater.
Typical tank-style water heaters are large units that hold an average of 40 to 80 gallons (about 151 to 302 liters) of water. It uses a thermostat to keep the water heated to a predetermined temperature. This large volume of preheated water provides access to hot water from multiple taps throughout the home at the same time. Tank-style water heaters are not energy efficient both because they keep the water constantly heated and because they have to heat large amounts of water once the tank’s supply is depleted.
Tankless water heaters are small units that can be mounted on floors, walls, and in between wall studs. They do not keep water in storage but instead heat water on demand. When a tap is turned on, the water flow activates a heating unit that heats the water as it flows through the unit. Tankless water heaters are more energy efficient than tank-style water heaters because they do not use energy to keep reservoirs of water preheated. This energy-efficient feature, however, means that tankless water heaters may not be able to meet the demands of delivering hot water to multiple taps at the same time.
A hybrid water heater has both a reservoir and an on-demand heating system. The reservoir tank is much smaller than the tank-style water heater, typically holding only three to eight gallons (11 to 30 liters) of water. Hybrid water heaters are more energy efficient than tank-style water heaters as the they keep only small amounts of water preheated. Like a tankless water heater, a hybrid water heater has a flow-activated water heating system. The combination of reservoir tank and flow-activated water heating system allows hybrid water heaters to supply hot water to multiple taps simultaneously.
Tank-style water heaters are the least expensive of water heater options, but they will use more energy over time than either tankless or hybrid water heaters. A tankless water heater is less expensive than a hybrid water heater but may require the installation of multiple units in order to supply hot water to several areas of a house. A hybrid water heater, although costly initially, is energy efficient and capable of working as a whole-house water heater.