A.O. Smith NEXT Hybrid Water Heaters (Tankless)

A product review of the A.O. Smith NEXT hybrid water heater, a combination tankless water heater and small storage tank.

A small buffer tank is the big improvement

The A.O. Smith hybrid water heater has a small "buffer tank". A.O. Smith isn’t saying what size the tank is, but rumors are that it is around 15 to 20 gallons.  With a buffer tank the unit can deliver hot water faster since it doesn’t have to heat the water first, there is sufficient hot water in the tank to begin sending water to the fixtures right away just as a storage water heater would do.  Before the buffer tank runs out of hot water the tankless heater gets up to temperature and begins supplying the hot water.

This also allows the burner to not have to fire with relatively small hot water uses, such as washing hands in a bathroom sink. The NEXT is a condensing type water heater with a 90% “thermal efficiency.” It has a secondary heat exchanger used to capture heat from the flue gas and put it into the buffer tank.

Hot Water Circulating Systems

It should also work with hot water circulating systems unlike most tankless water heaters.  The buffer tank should also eliminate the "cold water sandwich" that tankless water heaters are famous for.

High efficiency water heater

The NEXT Hybrid achieves a very high efficiency--it is rated at 90% "thermal efficiency." The high efficiency is achieved through a process in which a secondary heat exchanger is used to capture the heated flue gas from the tankless unit and route it back through the buffer tank to extract additional heat. So, not only does the buffer tank have benefits in terms of hot water delivery, but it also helps the NEXT Hybrid achieve its high-efficiency, condensing performance.

Tank standby loss

Since the heater has a storage tank it will have standby losses like a standard storage water heater, but they will be substantially smaller due to the smaller size of the buffer tank. It will probably have less than half the losses of a standard gas tank type water heater which puts it at around $2-$4 dollars per month in energy usage.