Water Heater Storage Type Options: How to Buy The Right Size and Type

Buyers Guide Storage Type

If your old water heater met your storage type and capacity needs, then there may not be a need to change. But you may want to consider the different options available. The best time to make changes to your water heater set-up is when it's time to buy a new one! With a little research, you'll be able to find the perfect match to meet your household's hot water needs.

Replacing your water heater is rarely how you want to spend your time or money, and there are many things to consider beyond how you will dispose of your old unit. For instance, you may want to consider transitioning to a tankless system, or in some rare situations changing fuel types may make sense. 

Another thing to consider is how well your old water heater met your household hot water demands. Did your showers run cold during peak periods? If so, you may want to consider purchasing a unit that will better meet your family's needs. Click HERE to read our water heater buyers guide. 

Water Heater Storage Type Options

Traditional Tank Style Water Heaters

The tank storage type is the most common style of water heater. They are very versatile and come in models that can operate on electricity, natural gas, and liquid propane. Some are even designed to use solar panels as a fuel source.

​These water heaters have an insulated tank where the water is heated and stored  until there is a hot water demand within the house. When a faucet is opened, the hot water flows from the tank to the faucet. Cold water then fills the tank back up to capacity where it's then heated and held until another hot water faucet is opened.  

​Tank capacity sizes vary from 28 gallons to over 100 gallons. If your old water heater wasn't able to keep up with your household hot water demands, there's a good chance that you either out grew your water heater or it was incorrectly sized from the beginning.

A correctly sized water heater will provide a nice balance between delivering enough hot water and operating in an energy efficient manner. Sizing is simply determining your household's hot water needs. It sounds hard, but it's actually not. ​

How to Size a Traditional Water Heater

The simplest method is to follow this rule-of-thumb chart. Remember, this is not an exact science and you should adjust accordingly to account for your family's individual hot water needs. 



Tank Size


2 people

45 to 55 gallons

3 people

55 to 65 gallons

4 people

65 to 75 gallons

5 people

75 to 85 gallons

6 people

85 to 100 gallons

7 people

100+ gallons

Recovery Rate

When selecting a traditional water heater it's important to consider the rate at which the unit is capable of recovering. 

Recovery rate = Number of gallons of water heated in an hour​

The recovery rate is frequently overlooked when choosing a water heater, however, it plays a big role in the unit's performance. If your household has a high demand for hot water, you'll want to select a water heater with a high recovery rate. 

Tankless Water Heaters

No buyers guide would be complete without a discussion on tankless water heaters - even though they really don't fall into the "storage type" category. A tankless actually doesn't store water, but rather it heats the water when there is a demand. This is why they are frequently called on-demand or instantaneous water heaters. 

Cold incoming water runs thru a heat exchanger and within seconds the water leaves the unit hot. Tankless water heaters are capable of delivering a seemingly endless flow of hot water since they are not limited by the size of a storage tank.

They are also more energy-efficient than their traditional tank-style cousins since they are not holding and heating hot water. In fact, the electric models frequently receive an efficiency score of 99%!

However, there is also less margin for error when sizing a tankless water heater. Without a storage tank to draw from if you exceed the units capacity, the tankless unit may not be able to deliver enough hot water.

How to Size a Tankless Water Heater

Sizing is determined by flow rate, which is basically the amount of hot water the unit is capable of delivering each minute. When sizing a tankless unit, these 2 factors need to be considered:

  • How many hot water points will be used at the same time.
  • The temperature rise (the incoming water temperature minus the outgoing hot water temperature)​.

The most common tankless water heaters deliver 3.5 gallons per minute, which is generally enough hot water to service 2 points simultaneously. In other words, a shower and a faucet.

Tankless units are designed to operate on electricity, natural gas, or liquid propane. Although the electric units are far more energy efficient, there are often electrical upgrades that must take place to the home in order to provide the amount of electricity necessary. 

Check out our detailed buyer’s guide on tankless water heaters HERE.

Point-of-Use Water Heaters

Point-of-use units are sometimes called utility water heaters. They are small tank-style water heaters that are frequently used in shops, garages or outbuildings, and they range in size from 2.5 to 19 gallons.

A common use for these types of water heaters is to provide hot water to a secondary bathroom that is located too far from the main water heater, and therefore is poorly serviced. If a point-of-use water heater is installed, the bathroom will have near instantaneous hot water since the heater will be so close. 

Mobile Home Water Heaters

Mobile homes have special requirements for water heaters. A  traditional tank-style water heater is usually not an option, although, some tankless models are rated for mobile homes.

A mobile home water heater is designed to specifically be used in mobile homes. They are also available in both gas and electric models. ​

RV Water Heaters

Recreational vehicles require a specially designed water heater to fit their limited space. There are many different type of water heaters for RV's. They range from a basic design to the sophisticated. 

RV's are frequently used for extended periods of time. Many "snowbirds" live in their RV's 6 to 8 months a year, so RV water heater's are designed to be compact and yet meet the hot water demand. Check out our article on RV Water Heaters.