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What Size Water Heater Do I Need?

3 sizes of water heaters Every household uses hot water, which is why it’s important to have a water heater. If you’re building a new home, or just replacing an old one, there are many things to consider when buying a new water heater. One of those is size. Different sizes work better for different homes and needs. Since there are so many sizes there, you may not know what you need. Keep reading to learn what size water heater is right for you!

Are There Different Types of Water Heaters?

The answer to this question is: yes! There are a few different types of water heaters. These can include:

  1. Traditional storage tank
  2. Tankless
  3. Hybrid
  4. Point-of-use

Each water heater has its own benefits, but we will mainly be focusing on the traditional storage tank water heater. These water heaters are among the most popular water heater options. They feature an insulated tank where water is stored and warmed. When referring to the size of a water heater, we are talking about this insulated tank.

What Size Water Heaters are Available?

different water heaters

Water heater tanks can hold anywhere from 10-100 gallons of water. There are typically tall and short water heaters. Tall water heaters range from 46 to about 60 inches tall and 20 inches in diameter. These can hold approximately 30-100 gallons. Short water heaters range from 30-49 inches tall, but are wider in diameter: about 20-26 inches. They can hold 30-50 gallons of water. Because of their height, “low boys” are usually installed in homes that have a crawl space instead of a basement.

Tankless water heaters are also an option if you’re low on space. These are much smaller units that don’t need a big bulky tank to produce hot water. These units are typically more expensive, but they save about 27—50% of fuel costs per year. Since there is no tank, the water is filtered in through a flow sensor and then the unit begins producing hot water.

So, What Size Do I Need?

The size of your water heater will differ depending on how much hot water you use. Each size is more beneficial for different households; typically the larger the family, the larger the heater. The size you get also depends on how much space you have and how much you can afford. You can estimate the necessary tank capacity based on the number of people in the house:

water heater size infographic

These numbers may not be accurate for you and your family’s needs. For example, some small families may regularly use multiple hot water appliances at once, while a larger family might not. Luckily, there is a way to measure how much water your household needs.

How to Estimate Your Needed Size

There are steps you can take to know what size water heater you will want to use.

1. Determine what time is your busiest “hot-water-using” hour

To figure out what size water heater you need, you first need to calculate the “peak hour demand.” This refers to the maximum amount of hot water your household needs during the busiest “hot-water-using” time of day. Typically, showers will use the hottest water compared to other activities/appliances. So, if most family members shower in the morning, that would be your peak hour.

2. Calculate the gallons of water needed

Now that you know the busiest time of day, think of all the hot water activities and appliances you would normally use during that time. There are some tools and charts you can use to calculate the gallons of water each activity uses. Once you add these numbers together, you have your peak hour demand. Shamrock Plumbing has a tool for you to easily figure out this number.

3. Choose a water heater

water heater on the wall

Once you’re ready to pick the right water heater, you’ll want to choose one that has a “first hour rating” (FHR) within 1-2 gallons of the peak hour demand. This number signifies the number of gallons of hot water the unit can provide in a single hour, starting with a full tank of hot water. So, if your FHR and peak hour demand match, your water heater will meet your hot water needs.

To find the FHR on a website, it will be listed under something like, “specifications,” “features,” or “performance.” If you’re looking at a physical water heater, you can find the FHR listed in the top left corner of the EnergyGuide label under, “Capacity (first hour rating).”

Contact Shamrock

Shamrock Plumbing is here to help with all your water heater needs! We have been trusted installation and repair experts in Utah for over 30 years. If you’re interested in learning more about what we can do for you, give us a call or request a quote!

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