What size water heater do I need for my home?

What size water heater do I need

A 40-gallon water heater can be enough for a small household of 2 to 3 people. A family of 3 to 5 can get by with a unit of 50 to 60 gallons. Households should estimate an extra 10 gallons for every head over five people.

There is always a running tap at home, whether from a faucet, bath, or shower for my wife and kids. Having gone through the stress of trying to find the correct water heater left me with a question I needed an answer to. What size water heater do I need for a family?

Finding the correct water heater for your family is more than finding the right size. Available space, energy consumption, first-hour rating, and device type are necessary considerations.

What size water do I need for a family?

A 30 to 40 gallon water heater is good for 1-3 family members. A 50-60 gallon water heater is good for 3-5 family members. A 60-80 gallon water heater is good for 5+ family members.

How To Quickly Select The Right Size Water Heater For Your Home

Storage tank water heaters are the most common. These storage tank heaters usually have a fairly set tank capacity. This makes it necessary to find the right-sized device to fit your family’s hot water needs.

The Engineering ToolBox has a handy table that determines each person’s daily hot water use in a house. 20 to 35 gallons per day is the rough value for a home or apartment. Peak demand (first-hour rating) is typically 10 gallons per hour.

After combing through this data, I found some answers! I came down to the conservative water heating device size of 50 gallons for my family size of 4.

Determining A More Tailored Water Heater Capacity

Some of us would prefer a more budget-friendly approach and desire more accuracy because the more significant the water heating tank, the heftier the price tag.

So, here’s a quick guide to determine the device size most tailored to your household size.

Firstly, figure out your heater’s first-hour rating (FHR). The FHR is the total amount of hot water it can supply in an hour, starting from a full tank.

This figure is dependent on the tank’s storage capacity, type of fuel source, and the size of the heating element. The manufacturer should provide this appliance information. See the machine’s EnergyGuide label or the other informative tags. 

The fuel source is usually overlooked in water heaters, but it is essential. Different fuel sources are available, but the most common include electric, natural gas, and liquified petroleum gas.

However, if you are even more cost conscience than I am, then the most efficient and sustainable type of water heater is a solar water heater. This type of water heater can even save space by being on the roof. While not so common in North America, they have become quite common in other world areas.

Note Your Family’s Peak Hour Demand

This dubious sounding heading means finding out how much hot water your house uses at its busiest hour during the day.

This peak hour usage is usually during the morning rush hour for most families. The peak hour usage is when multiple people are trying to get ready for work or school, which often means various showers, shaving, brushing teeth, and perhaps running the dishwasher.

If you haven’t been conscious of the amount of hot water you use, keep a journal. Take notes for a week and see what appliances were used, the number of showers, and other hot water activities during your peak hour demand.

Consolidate Your Hot Water Usage

Once you can pinpoint your peak hour usage, you can move on to work out a more scientific estimate of the gallons of hot water your family consumes.

You take the activity (shower, shave etc) and multiply it by the number of times used in the peak hour. That gives you the gallons used per hour (activity x number of times used = gallons used per hour).

Here’s a nifty check on the average amount of hot water used by the most common house activities:

  • A single shower uses 10 gallons
  • Shaving uses 2 gallons (4-5 min shave)
  • A dishwashing cycle runs 6 gallons
  • Prepping food or washing a few dishes by hand uses 4 gallons, 2 gallons per minute
  • Running a washing machine uses 7 gallons

In practice, a family of 4 all taking showers in the morning with a single person shaving, plus someone preparing lunch and a quick load of washing looks something like this:

Activity x number of times used = gallons per hour

  • Shower x 4 = 40 gallons
  • Shave x 1 = 2 gallons
  • Lunch prep x 1 = 4 gallons
  • Automatic washing machine x 1 = 7 gallons

The total peak hour demand is then 53 gallons per hour.

Inspect The Heater’s EnergyGuide Label

It is good to know that some manufacturers of water heaters have actual calculators on their websites that consider these factors and other use-case scenarios. You can also look over the EnergyGuide Label, an appliance requirement for all manufacturers. 

This yellow sticker with black font won’t only show you the machine’s first-hour rating, but it will also estimate the amount of energy it uses compared with similar models. 

There are also general annual operation cost data on the label.

No Space For A Tank Water Heater?

The traditional tank water heaters are great for many things, but they aren’t the best for houses with little to no space. If your home is reminiscent of the New York City dream and doesn’t allow for more than what’s necessary, then you may want to consider a tankless water heater.

Tankless water heaters are a superb alternative as some 50-gallon tank-designed water heaters are as high as 6 feet and measure 22 inches in diameter.

A 50-gallon tankless water heater, also known as an on-demand water heater, would have a similar output but take up a fraction of the real estate. 

Tankless water heaters heat the water when it passes through the machine instead of heating and reheating a water tank every time the reservoir is used up.

Choosing the correct size tankless water heater is a more involved process but not one that’s too dissimilar from the tank sort heater.


Choosing the proper water heater size for your family doesn’t have to be another stressful ordeal, but picking the incorrect size can be.

Before shopping around, note your peak hour demand and jot down the activities that contribute the most during this one hour. Plugin that information into the easy formula provided by Energy Saver, and voila! You are in business.

Frequently Asked Questions (FAQs)

Is a 50-gallon water heater enough for a family of 4?

A 50-gallon water heater is typically enough for a family of 4. However, it is essential to note that usage habits may affect this estimate.

How many gallons of hot water does the average family use?

The average family uses around 50 gallons of hot water per day. However, usage habits may affect this estimate.

How do you know what size water heater to get?

Your peak hour demand will determine the size of your water heater. To calculate this, you will need to consider the number and types of hot water activities in your home.

What is the first-hour rating on a water heater?

The first-hour rating is the amount of hot water that a water heater can produce in an hour. This should be considered when choosing a water heater, as it will affect the amount of hot water available to your home.

What are the annual operating costs for a water heater?

The annual operating costs for a water heater will be determined by the size and type of water heater you choose. The operating costs can be found on the EnergyGuide Label, which is required for all water heaters.

Is a 50-gallon water heater enough for a family of 7?

A 50-gallon water heater is not typically big enough for a family of 7. A family size of 7 should require a 60-80 gallon tank for optimal hot water usage.

Is a 40-gallon water heater enough for a family of 4?

A 40-gallon water heater is typically enough for a family of 2-3 people. If you are a family that doesn’t use a lot of water or prefers not to waste hot water, then it may be just enough to work for a family of 4. If you are unsure how much hot water you will use throughout the day or during your peak hour demand, it is probably safer to go with a 50-gallon water heater.

How many showers can you have in a 40-gallon tank?

The average shower uses 20 gallons of hot water in an hour, so a 40-gallon water heater can provide up to 2 showers in a one-hour period if other activities are using no hot water.

The H2Home Lab team is dedicated to helping you find the best solutions to your specific water needs, as well as provide troubleshooting tips and guides for water filtration, heating, softening and plumbing. We hope you will find the info you need on our site from any one of our buying guides or subject matter articles.

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