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Water Heater Dimensions: Finding The Right Water Heater For A Tight Space

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Installing a water heater inside can mean giving up some valuable living space. You should want to keep it out of sight as the appliance can become an eyesore.

Consider a closet or a typical low overhead area so it remains close but discreetly hidden. 

If you have a designated space that you believe is ideal for a water heater, you should measure it first to ensure the dimensions are a good match depending on the type of water heater you go for. 

In this guide, we will look at why the dimensions of your water heater should be considered, how you can determine them, and how the sizes may differ based on the type of water heater.

Why The Dimensions Of Your Water Heater Should Be Considered

Where you plan on installing your water heater is of prime importance as it can take up a large space.

This may not be a problem if you plan on putting it in the garage or basement yet in your living space or any other tight space then the dimensions and required capacity can soon add up.

For a closet in your kitchen or living room, or even a tight space in the attic, the dimensions of your water heater could be critical. 

If you cannot guarantee the space to sufficiently house your water heater in the space you want it in then you have to find somewhere else which may become a hassle.

It could just about fit but even then you may not have enough space to complete any maintenance. If the space is indeed too tight then it will likely contravene the building or plumbing codes for your State. 

Those building and plumbing codes are important to think about when you get to install your tank-style water heater when you do want it to fit in a tight spot such as a closet.

Find out what those building and plumbing codes entail before you install your water heater as you need to ensure the correct clearance space so that the appliance operates as it should.

There may also be some specific guidance in the manual that came with the water heater to guide you through how much clearance space you need. 

There is one simple distinction between a gas and electric water heater and that is although they are similar in size, a gas water heater will require more space.

This is purely due to the necessary airflow to guarantee that the combustion is safe.

It would be recommended that you find an open space such as a garage or basement to install your water heater yet if not you have to ensure an appropriate clearance space is available in your closet.

How You Can Determine The Dimensions Of Your Water Heater

Forget getting out your tape measure just yet as there are other ways of checking this. A simple way to determine the dimensions of your water heater is to check the owner’s manual that came with it.

All you need to know is the depth, width, and height of that water heater then find out what the clearance space should be to determine the required dimensions.

While you may be able to easily measure your water heater, you need to take into account the additional clearance space which is required for safe operation. 

There is the capacity to think about as well as the dimensions and a typical 50-gallon water heater should be relatively tall with an equal depth and width.

The height will be the measurement from the top to the bottom of the water heater. Of course, for a round water heater, the depth and width will be the same as it will be the distance from the center of one side to the opposite one. 

To have a capacity of 50 gallons, you can expect a height of around 60 to 65 inches with a depth and width of around 18 to 20 inches. 

Then you should take into account the clearance space for your heat heater for it to operate safely, with more space required for a gas-powered water heater. 

What Size Of Water Heater You Should Consider

What Size Of Water Heater You Should Consider

The size and dimensions of your water heater may be determined by how much water you expect to use at various times of the day.

For instance, a small household of just one to two persons should only need between 30 and 40 gallons (114 to 151 liters). 

Going further up, a household of two to three people should require more water at around 40 to 50 gallons (151 to 189 liters).

Finally, a household of around three to four people should need 50 to 60 gallons (189 to 227 liters) of hot water. 

Depending on the type of water heater you go for, there may be different calculations to work out based on how it operates and the fuel source.

This can differ between a solar water heater, a tankless water heater, and a storage/heat pump water heater. 

The Sizes Of Solar Water Heaters

Determining the dimensions of a solar water heater can be a little complicated as it involves working out the total collector area and the storage volume.

Both measurements are required to be upwards of 90% of your home’s hot water requirements during summer. 

However, these requirements are typically performed by the contractors for your solar system using a range of computer programs and worksheets so you may not have to work this out yourself. 

The Collector Area

The collector area is typically worked out by allowing for 20 square feet for each of the two first family members.

For any more members of the household, you can expect to add another eight square feet for each one if you reside in the US Sun Belt area. This can be as much as 12 to 14 square feet if you live further north.   

The Storage Volume

The storage volume is also determined by how many people reside in the household. For one to three people, you can use a small storage tank that has a capacity of around 50 to 60 gallons. 

For up to four members of a household, you can typically use a medium-sized storage tank of around 80 gallons while a larger tank at around 100 gallons should suffice for up to six people in a household. 

How big the storage tank is working with the collector area and you should expect around 1.5 gallons for each square foot of the collector area.

Let’s say there’s a family of four in the household, for that, you would need a collector area of 56 square feet if they reside in the US Sun Belt Area and 64 to 68 square feet if they live north of the US Sun Belt Area. 

A collector area of 56 square feet would require a storage tank of 84 gallons while north of the US Sun Belt Area would require more gallons of water in the storage tank, around 96 to 102 to be exact. 

You may even use a different calculation if you live in a sunny and warm climate.

If you do, the ratio changes from 1.5 gallons per square foot of collector area to 2 to prevent overheating in times of low demand for hot water.

For a family of four that could mean a storage tank of 112 gallons in the US Sun Belt Area and as much as between 128 and 136 gallons if you reside north of it. 

The Sizes Of Tankless Water Heaters

The Sizes Of Tankless Water Heaters

A tankless water heater should be a popular option due to its energy efficiency and low operating cost. They only provide hot water when it is needed by using a gas burner or an electric element.

As soon as you open a hot water faucet, the cold water will move through that pipe and is then heated to flow out as hot water. 

There’s little wait for hot water and a tankless water heater can be installed on the wall or in a tight space.

It’s not exactly the size of the tankless water heater that is important, but rather its capacity for heating enough hot water. 

When you do try to calculate the dimensions of tankless water heaters, you should realize that they are rated by the possible maximum temperature rate at a given flow rate.

The flow rate can be limited by the output of a tankless water heater so try not to take a shower while the dishwasher is running.

Once you work out the flow rate and that temperature rises then you can work out the required dimensions. 

The Flow Rate

To work out the flow rate, you need to work out the hot water usage at its peak which could be when everyone wants a hot shower in the morning or the evening.

The flow rate is how many gallons of water these appliances will use every minute, which is measured as GPM or gallons per minute. 

Typical flow rates for various appliances can be a dishwasher and washing machine will be 3 GPM while the shower will be 2.5 GPM.

That peak hour is likely to be in the morning while someone is running the dishwasher while the shower is being used so you can expect to use 5.5 GPM so look for a water heater with that flow rate.

The Temperature Rise

The temperature rise can also be calculated easily by running the cold water faucet for a few minutes and then measuring the temperature with a thermometer.

The hot water temperature in a home should be about 110°F so all you need to do is minus that cold water temperature from the 110°F to find out the required temperature rise.

Let’s say that your cold water temperature is 60°F, you will need a further 50°F to reach 110°F so that’s your required temperature rise.   

You should expect an electric tankless water heater to be smaller than its gas counterpart.

They may not be as powerful as a gas tankless water heater though you can expect to pay less on the running costs and the installation. 

A typical electric water heater would have a depth of 3.5 inches, a width of around 17 to 18 inches with the height being slightly bigger at 18 to 19 inches.

You should see an electric water heater as compact and exceedingly energy efficient

The Sizes Of Storage/Heat Pump Water Heaters

For a storage water heater, including one that has a heat pump water heater and a tank, you can determine the required size by working out its first-hour rating.

This is the number of gallons of hot water the heater can supply with a full tank per hour.

To calculate that, you need to know how the water is heated, the size of the electric element or gas burner, and the tank capacity. 

Thankfully, the Federal Trade Commission has made it a requirement for an EnergyGuide label to list the first-hour rating on any new conventional storage water heater.

Alas, that is not the case for a heat pump water heater though it may be included in the owner’s manual or another part of the product literature.

You should look out for a water heater that has a first-hour rating that matches the peak-hour demand, which is likely to be in the morning or evening. 

The Peak Hour Demand

For instance, the peak hour demand could well be in the morning when more people are taking a shower.

On average, a shower uses up around 20 gallons of hot water so if two people were to take a shower in that first hour, that would amount to 40 gallons. 

You could also have the dishwasher on at the same time which uses up another seven gallons of hot water which adds up to 47 gallons for the peak hour demand.

Your water heater should have at least a rating of 47 gallons.  

Final Thoughts

There are three main types of water heater to think about which include solar water heaters, storage/heat pump water heaters, and tankless water heaters.

Depending on the type of water heater you go for, there are various considerations to make to work out how big a space you need to provide. 

This could be in the capacity measured by gallons, the physical dimensions in square inches, and then you have to include the clearance space for a gas water heater.

Whichever type you go for, ensure it has ample space as you will need to have room to be able to perform regular maintenance too. 

Frequently Asked Questions

How Long Should Water Heaters Last?

An average water heater should be expected to last for between eight and 12 years though this largely depends on the installation and the water quality.

The size and design of the water heater can also be factored into the lifespan. If your water heater has been operating for a decade or more then it is probably due to being replaced. 

What Is The Ideal Way To Install A Water Heater?

If you are installing an electric water heater then you should first move it into a drain pan and then install the temperature and pressure relief valve (also abbreviated to the T&P valve) with the discharge pipe. 

You can next attach the hoses and the water heater can be filled when the aerator is removed and the water supply is turned on.

Finally, connect the wiring and double-check that the tank is full when you turn on the faucet.

A gas water heater is installed a little differently as you will need to disconnect both the gas and the water lines and then detach the gas exhaust.

Get the water heater in the correct position then install both the water line connections and the heat valves before attaching the gas line.

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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