How to Choose the Right Water Heater Dimensions

A water heater is what you’d want when you need a shower on a cold, foggy morning. It’s not surprising that many families have water heaters installed in their homes. If you’re one of those people shopping for one, then you may likely be researching water heater dimensions. This is important because you need to know water heater sizes first before deciding that water heater you’d have installed in your home.

Two Types of Water Heaters and Their Sizes

Water Heater Types and Their Sizes

Water heaters are categorized into two—storage and tankless. This is important to know because you need to determine first the type of water heater you want before even determining the right size of the water heater.

A tankless water heater is also called an on-demand water heater. It produces hot water only after you call for it. This means turning on the faucet, switching on the dishwasher, or starting a cycle on the washing machine. It comes with built-in coils designed to heat water when you need it.

There are certain advantages of using a tankless water heater. One is that it is more energy-efficient since there is no standby heat loss. It can also provide you hot water on demand. But the problem with this type of water heater is that it can only give you a limited amount of hot water—around 9.8 gallons—per minute. Moreover, the upfront cost of installing it can be quite prohibitive.

On the other hand, a storage-tank water heater is the most commonly available and used type of water heater. It comes with an insulated tank where the hot water is stored until it is needed. With a storage-tank water heater, you won’t have to worry about running out of hot water. It’s also cheaper and best suited for large households. But the main problem with this type of water heater is that it is not as energy efficient as the tankless water heater.

How to Choose the Right Water Heater Sizes

With numerous sizes of water heaters available in the market, you must determine your average water consumption so you can determine the right size for you. Also, you must keep in mind several key factors in determining water heater sizes.

Fuel Source

For one, take into consideration your fuel source. Would it be electricity, liquid propane or natural gas? Will the water heater be connected to the broiler? Determining the fuel source will help you in narrowing down your options and enable you to choose the right water heater size.

Household Size

Another consideration is the household size. Do you belong to a large household with more than 10 people? If so you would need a higher-capacity water heater so that multiple people can do tasks at the same time, whether it’s running the dishwasher, doing the laundry or taking a bath.

Or do you live with just a partner and one child? If so then you can settle for a water heater with a lower capacity. These are some of the scenarios that can guide you in determining the right size of a water heater for you.

Now, if you have 1-2 people in your home and you are opting for a storage-tank water heater, you can opt for a unit with at least a 30-gallon capacity. It’s recommended that you get a storage-tank water heater with at least 40 gallons if you live with two to three people.

For families with three to four people, you would be better off with a water heater that has a 50 gallons capacity for the electric model and 40-gallons for those that use natural gas or liquid propane.

Now, if you have a large family with six or more individuals, it is recommended that you opt for at least an electric model with an 80 gallons capacity. If you are opting for natural gas or liquid propane, then you should get one with a capacity of 50 gallons.

You must also remember or know that the sizes of storage tank water heaters are based on BTU input and capacity in gallons. Therefore, the more regularly you need hot water, the higher capacity and BTUs you’ll need for home consumption. Let’s say that that four people in your household would be taking 10-minute showers in an hour.

Therefore, you would be using about 40 gallons of hot water. If you get a storage-tank water heater with a lower capacity than 40 gallons, your tank would be emptied with the third or fourth person not finishing his or her shower. In short, you must take into consideration the daily routine of your household members when selecting the tank size.

Flow Rate and Temperature Rise

But how about going the tankless route? Since a tankless water heater does not store water, then you won’t have to be concerned about the capacity size. But there are two factors that you would have to be mindful of—flow rate and temperature rise.

In determining the water heater flow rate, you should add up all the flow rates of the appliances you would likely be using at the same time. Then subtract the incoming temperature from the outgoing water temperature to determine the necessary temperature rise.

Let’s say that the incoming temperature is 50 degrees Fahrenheit and the desired outgoing temperature is 50 degrees, then you must get a tankless water heater that has a temperature rise of 50 degrees.

Using this temperature rise, below are the sizes you’d need for a tankless unit:

  • At least 3.5 GPM for 1 to 2 fixtures used at the same time
  • At least 5 GPM for 2 to 3 fixtures used at the same time
  • At least 7 GPM for 3 to 4 fixtures used at the same time


A water heater is a must-have if you live in a cold climate country. There are two types of water heater- storage and tankless. The size of a storage water heater would depend on the number of people who will be using the heater. On the other hand, you’ll need to consider the temperature rise and flow rate of a tankless water heater to determine the right one for your home.