A storage tank heater functions by storing around 30-55 gallons of water in the tank. The water is kept heated at all times. On the other hand, a tankless water heater, uses either a gas or electric heat source to heat the water on demand. They are also known as on demand water heaters.



1. Cost:

A tankless water heater is much costlier than a storage tank heater. Storage water heaters can be bought and installed for a half of the cost of installing new tankless heaters.

The initial installation costs may be higher, but tankless water heaters can be 25-34% more energy efficient than storage tank heaters. Since water is heated only on a as need basis, this kind of heater is less expensive in the long run.

With storage water heaters, the tank is first filled with water, heated and then stored. It is costly to keep the water hot, all the time. Tankless water heaters heat only a small quantity of water each time, and so the cost is reduced. This offers amazing long term savings on your utility bills.

2. Space:

There is a notable difference in the size of a storage tank heater versus a tankless heater. A storage water heater, on an average, holds around 40 to 60 gallons of water and measures around 60 inches tall. Because of the size and bulk, they take up loads of space.

A tankless water heater is only 19 to 29 inches in size, making it smaller and more compact. Hence, this kind of system can be installed in smaller areas, giving up space for other items.

3. Service And Maintenance Repairs:

Both storage tank heaters and tankless water heaters, should be cleaned and serviced annually. The yearly maintenance will cost the same for both the systems. However, tankless water heaters have notably higher maintenance needs than storage tank heaters. There are 2 reasons that maintenance can be more expensive for tankless water heaters.

A. Tankless water heaters have heat exchangers that are extremely sensitive to hard water. They need to be de-limed every year or so. This is a two hours service call for a plumber. It is not like a simple ‘flushing’ with a storage heater.

B. Tankless water heaters should be serviced every year without fail. If neglected, it will break down quicker, and will need repairs very frequently.

4. Instant Hot Water :

A great advantage of tankless water heaters is that they supply hot water instantly on demand. The hot water never runs out, which is great for large families. There is no stand by loss. Since the hot water is not stored in a tank, there is no heat loss, when the heater is not operating.

With a large family using a storage tank heater, hot water will stop at some point. With a tankless heater, this will not happen.

5. Flexibility and Durability:

With a storage tank heater, it is possible to take a shower and wash the dishes at the same time. It is possible to do 2 or 3 tasks at the same time. This is not possible with a tankless water heater, unless you have 2 or 3 tankless heaters.

A tankless heater will last up to 20+ years. On the other hand, a storage tank heater, will last up to 10 to 12 years. This means you need to purchase them twice as frequently as a tankless water heater.

For people, thinking of buying a water heater, all these factors should be considered before making the purchase.


Written by: Sangee_sks


Find more information about water heaters at Energy Star

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