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Water Heater Dimensions: Finding the Right Water Heater for a Tight Space


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If space is limited, knowing the water heater dimensions can ensure that it'll fit. This is particularly important if your water heater will be installed in a tight space such as a closet or other low over-head area. There's nothing worse than purchasing a new water heater only to find out that it's too large for the designated space.

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This article will help you determine your water heater dimensions and cover the different types of water heaters to so you can find a size that best meets your needs. 

Why Water Heater Dimensions Matter

As you might expect, the water heater's dimensions are not nearly as important if you'll be installing your new heater in a basement, garage or other location with plenty of space.

However, if your water heater will be installed in a tight place, such as an attic or closet, then it's critical to know the dimensions of your new water heater.

A new water heater that's too large for the installation location will either not fit at all, or not provide enough space to be able to perform the necessary preventative maintenance. And worse, it likely won't meet the building codes for your State.

Clearance Space

When installing your tank-style water heater in a closet or other tight space, it's important to follow your local plumbing codes to ensure you have the necessary amount of clearance space for your appliance to operate properly and safely.

In addition, you'll need to check your owners manual. Most manufacturers provide details on the amount of clearance space required to safely operate their water heaters.

Gas and electric water heaters are usually similar in size, however a gas heater will need additional space to allow for the air flow required for safe combustion.

Although we highly recommend installing your water heater in an open space, such a basement or garage, sometimes that simply isn't an option. If your only location alternative is within a closet, we recommend reading this article and consulting with a professional plumber.

How to Determine Your Water Heater Dimensions

All manufacturers print the water heaters dimensions in their sales material/owners manual so there's no need to go from store-to-store with your tape measure!

But knowing how the dimensions are determined will help you understand the space your new water heater will require to operate safely.  

A manufacturer will typically list the depth, width, and height of the water heater. These dimensions should give you enough information to determine if the appliance will fit within the allotted space.

Rheem PROE50 T2 RH95

The Rheem PROE50 T2 RH95 is a popular electric 50 gallon water heater. Let's take a look at this water heater's dimensions.

According to Rheem's sales material, this water heater has the following dimensions:

  • Depth: 20.25-inches
  • Width: 20.25-inches
  • Height: 61.63-inches

But what do these measurements mean and how are they determined?

The water heater's height of 61.63-inches is pretty straight forward. It's simply the measurement from the bottom of the water heater to the top.

And since the water heater is round, it's not surprising that the depth and width dimensions are the same. Each of these measurements represents the distance from the center of one side to the center of the opposite side.

Or, if you want to do a little math you can determine the width and depth diameter by measuring around the water heater, otherwise known as the circumference. This video will explain.

Watch the Video

Although, keep in mind that these water heater dimensions do not account for the additional clearance space necessary for your new appliance to operate safely. 

Are Water Heater Dimensions Standard?

Water heater dimensions vary from one manufacturer to another, and even from model to model. Although at first this may seem like a nuisance, it can actually be helpful and give you more options for tight installations.

For example, the A.O. Smith GCR-50LP ProMax Plus is a 50-gallon liquid propane water heater. Its dimensions vary slightly from the Rheem heater we looked at above.

As you can see below, they're very close in size, but not identical. When installing a water heater into a tight space, having an extra inch can mean the difference between fitting and not fitting.

Rheem PROE-50

A.O. Smith GCR-50Lp










In this example, you'll notice that each water heater has similar dimensions, but they're slightly different.

This is true with other water heater capacities as well. It's not surprising that you'll find 40-gallon water heaters to be smaller than 50-gallon units, and 80 gallon tanks to be larger.

You really just need to dig into the sales literature and find the size that'll fit your designated space and allows for enough clearance to safely operate.

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New Water Heater Regulations 

In 2015 manufacturers were required to meet new water heater regulations from the US Department of Energy, and every new water heater needed to meet a higher efficiency rating. Although these changes did increase the price of water heaters, it also meant that they required less energy to operate, in essence, saving saving you money every month in utility costs.

What does this mean?

Well, if you're replacing a pre-2015 water heater, in order to meet the new requirements, your new water heater will be larger.

In other words, you may be replacing a 50-gallon water heater, but the new sizes will no longer fit in your designated location. You may need to purchase a 40-gallon water heater instead, or you could choose to upgrade to a tankless water heater.

The video below goes into more detail on the changes and challenges.

Watch the Video

Short and Tall Water Heaters

Manufacturers also offer water heaters with different dimensions than the "standard" sizes. These heaters are designed with dimensions to fit into spaces with limited headroom. But don't be fooled by their size, they offer the same level of performance as a standard-sized unit.

Short Water Heaters

Short water heaters are also called lowboys because they are shorter and wider than a standard-sized heater.

A lowboy water heater ranges in height from 30 to 49-inches and frequently has a diameter between 20 to 26-inches. They can be found in capacities of up to 50-gallons and require a wider diameter to overcome their shorter height. 

As with all water heater installations, you'll need to factor in the necessary plumbing connection space. But as an added bonus, lowboys tend to be more energy efficient than standard or tall water heater.

Short water heaters are an excellent choice if headroom is an issue, so they work great in crawlspaces, attics, and even under cabinets. 

Tall Water Heaters

Tall water heaters typically range in height from 50 to 76-inches, and most have a diameter between 18 to 21-inches. A tall water heater isn't a good fit for a tight installation, but are excellent for places such as garages and basements where there's plenty of head room. 

Because of their larger size, they have a higher tank capacity and can hold up to 100-gallons. This makes them ideal for homes that require large amounts of hot water.

Narrow Water Heaters

As we've discussed, water heaters come in different dimensions based on their capacity and manufacturer.  So it's not surprising that some units are narrower than others. 

If you are replacing an old narrow water heater, it's possible that you won't be able to find one of the same dimensions. This is largely because of the new water heater regulations of 2015.

Over the years, manufacturers have worked to improve the energy efficiency of water heaters and one of the ways they do this is by increasing the amount of insulation around the tank.

As a general rule, it's unlikely that you'll find a tank-style water heater less than 16-inches in diameter.

Tankless Water Heater Dimensions

Tankless water heaters take up far less space than their tank-style cousins, which makes them an appealing alternative for households where space is extremely limited. In addition, they are mounted on the wall so they don't require any floor space!

But there are plenty of other advantages to installing a tankless water heater, such as unlimited hot water and improved energy efficiency. 

Gas Tankless Water Heaters

Gas tankless water heaters are larger than electric models, but much smaller than tank-style heaters. In addition, there are outdoor models, which for the most part, solves the limited space problem all together.

Rinnai RUR98iN

The Rinnai RUR98iN is an indoor natural gas tankless water heater that's more than capable of delivery hot water to your entire household.

The Rinnai RUR98iN tankless water heater dimensions:

  • Depth: 10-inches
  • Width: 18.5-inches
  • Height: 26-inches

Of course, just like a tank-style water heater you'll need to plan for the appropriate amount of clearance space for the unit to operate safely.

Electric Tankless Water Heaters

Electric tankless water heaters are by far the smallest of all water heaters, they also require the least amount of maintenance. These systems aren't as powerful as a gas tankless heater, but unless you have a very high demand of hot water you shouldn't have a problem finding one that can service your home.

Another advantage of electric tankless water heaters is their price. You can purchase a quality electric tankless for far less than a gas tankless, and spend about a third of the cost having it installed.

Rheem RTEX-24

The Rheem RTEX-24 is a popular electric tankless water heater, that can handle most household's demand for hot water.

The Rheem RTEX-24 electric tankless water heater dimensions:

  • Depth: 3.5-inches
  • Width: 17.63-inches
  • Height: 18.25-inches

The small, compact size of an electric tankless water heater is ideal for tight spaces, but don't let their small size fool you. They can deliver large amounts of hot water and they're also over 99% energy efficient. This means that 99% of the energy used goes into heating your water!

Final Thoughts

Finding the right sized water heater for your space is an important part of your buying decision. You'll want to investigate the plumbing codes in your area to ensure that you provide enough clearance space for your new water heater to safely operate, and have enough room to perform routine preventative maintenance.

If you're considering switching from a tank-style water heater, we highly recommend reading our tankless water heater buyers guide, as well as our article on gas vs. electric. It's a big decision and you'll want to do your homework before diving in.

Buying a water heater is an important decision, and there are plenty of things to consider. Many homeowners choose to hire a professional plumber to help them make the best decision for their household.

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