Water Heater Dimensions (Types & Sizes Guide)

Here’s our water heater dimensions guide, including different electric and gas-powered tank capacity dimensions and tankless hot water unit sizes.

There are two types of water heaters, electric and gas-powered models, and considering space-saving, the electric-powered ones are most efficient.

Knowing the type and size of the hot water unit you need allows you to understand how much garage or basement space the water heater tank will use.

Standard Water Heater Size 

Water heater dimensions are not as crucial if the installation will be done in a large basement, garage, or any open space in a home. However, it would matter if the area is cramped, and choosing a heating tank size that can fit in the free space is needed. 

If the water heater you have chosen is too large for the area, not only will the homeowners have a problem with making space to provide needed maintenance or repairs, but a too-large tank for a confined space might not meet the requirements of the building codes in a particular state.

A heating unit’s size will vary from one model to another depending on tank capacity, brand, the types of water heaters used, and whether you will be utilizing a gas or electric-powered one. This can be an issue at first, but the dimension difference will give you more options and flexibility regarding what tank diameter will fit your space. 

Some heating systems can have the same water capacity of 50 gallons but can differ in measurements.

To illustrate, the Rheem PROE-50 has a depth and width of 20.25 inches or 51.44 centimeters.  On the other hand, another 50-gallon tank, the A.O Smith GCR-50Lp, has a depth and width of 22 inches or 56 centimeters. 

The almost 2-inch or 5 5-centimeter difference of the PROE-50 will make it more appropriate for a smaller space compared to the GCR-50Lp. 

30 Gallon Water Heater Dimensions

A water heater with a capacity of 30 gallons is sometimes shorter than the higher capacity tanks. For the shorter ones, they are also sometimes called lowboys for their shorter and broader structure.  

The lowboys can range in height from 30 to 49 inches or 76 to 124 centimeters with a diameter of 20 to 26 inches or 51 to 66 centimeters. 

However, for a specific model, there is the Rheem Performance Atmospheric model with a capacity of 30 gallons. They are 46.25 inches in height or 117.5 centimeters and 19.75 inches or 50.2 centimeters in diameter. These heatering tanks weigh at least 112 pounds or 50.8 kilograms. 

Another option is the Rheem Marathon Electric heater which is 49.5 inches in height or 125.7 centimeters and a 21.63 inches or 54.9 centimeters in diameter. This unit weighs 75 pounds or 34 kilograms, leaps and bounds lighter than gas-powered ones. 

For smaller water heaters, you must be mindful of the plumbing connection space before installation. A considerable benefit of lowboys is that they are more energy-efficient than their taller counterparts. 

If you have smaller families and even smaller headroom, this is the product for you. You can install lowboys on any crawlspace and even under your kitchen cabinets. 

40 Gallon Water Heater Dimensions

Water heaters are available in many sizes, whether you need 30 gallons or even up to 100 gallons in capacity. 

However, if you are shopping for one on the internet or in the store, you might notice that many brands carry products with a 30-gallon capacity. The 40-gallon capacity is perfect for a household with 2 to 3 persons.

This unit is also often one of the taller water heater heights. Such tall heating tanks can have a height of 50 inches or 127 centimeters, while the diameter will range from 18 to 21 inches or 46 to 53 centimeters. 

The Reliance 40 Gallon 35500 GasHeater has a dimension of 20 inches or 51 centimeters in depth and diameter. The height is 62 inches or 157 centimeters. 

Another one is the A.O Smith 40 Gallon Gas heating unit which comes in dimensions of 18 inches or 46 centimeters for both diameter and depth, with a height of 58.25 inches or 147 centimeters. 

50 Gallon Water Heater Dimensions

A water heater with a capacity of 50 gallons or 189 liters is perfect for a family with three to four people. Although it could work for a family of five, it’s safer to take the capacity up a notch just to be safe. 

A popular choice is the 50-gallon Rheem Marathon Electric Water Heater. This unit has dimensions of 47.25 inches or 120 centimeters in height, with a diameter of 28.25 inches or 71.8 centimeters. It weighs 95 pounds or 43.1 kilograms. 

There is also the Rheem Professional Prestige, which is narrower than the wider former one. This heating tank has a height of 61 inches or 154.9 centimeters with a diameter of 22.25 inches or 56.5 centimeters. It weighs a heavy 218 pounds or 98.9 kilograms. 

The last is a 50-gallon capacity with a height of 50.5 inches or 128.3 centimeters, a diameter of 50.5 inches or 128.3 centimeters, and weighing at 160 pounds or 72.6 kilograms. 

Tankless Water Heater Dimensions 

If you have a smaller space in your home but need a water heater with a higher capacity, there are the electric-powered ones.

They are generally smaller than their gas-powered counterparts, but if these are still bigger than what your space would allow, then what you might be looking for are tankless water heaters. 

Tankless are even mounted on the wall, so there’s really no problem if no floor space is available. Aside from that advantage, a tankless unit also provides unlimited water capacity coupled with being energy-efficient!

For tankless water heaters powered by gas, there is the Rinnai RUR98iN with a depth of 10 inches or 25 centimeters, a width of 18.5 inches or 47 centimeters, and a height of 26 inches or 66 centimeters. 

If you want a smaller one, an electric-powered tankless device is there not to take up too much of your wall space. Note that these are not as powerful as gas-powered ones but should be enough if the demand is not that high.

A standard electric-powered tankless water heater has a depth of 3.5 inches or 9 centimeters, a width of 17.63 inches or 45 centimeters, and a height of 18.25 inches or 46 centimeters. 

How Much Space Does A Water Heater Need?

A water heater will need space for air circulation, especially if you have a tank powered by natural gas or propane. 

This clearance space should at least be 12 inches or 30 centimeters on each side if you intend to install a hot water cabinet around the tank. This number will double for the rear and front end of the tank, especially if the tank is gas-powered. 

In terms of the area of space needed for an average water heater tank, the diameter of the tank is what would matter to get this number. However, a one-meter space in your garage will be sufficient for a single tank. Go to our water heater closet dimensions guide here.

A tankless water heater, on the other hand, would not even require any floor space.  However, most home improvement stores do not usually mention that a tankless heater installation needs an electric service upgrade.

For the installation, a licensed electrician or contractor may need to assess your electrical system and potentially upgrade the electrical panel to ensure the unit has the adequate 40 to 60 amps or more of power needed.

As an example, when low amperage comes on, it can affect the voltage level. So, if this is installed without upgrading, any sudden voltage level drop can lead to the blinking of lights.

Visit our guide on tankless water heater pros and cons for more related content.