Enter the number of people in the household, the average time of each shower, the gallons of water used per minute by the showerhead, and the recovery rate of the water heater into the calculator to determine the heater size.

Water Heater Size Formula

The following formula is used to calculate the size of a water heater needed. 

HS = (N * T * G) / R

Variables:

  • HS is the heater size in gallons
  • N is the number of people in the household
  • T is the average time in minutes of each shower
  • G is the gallons of water used per minute by the showerhead
  • R is the recovery rate of the water heater (gallons per hour)

To calculate the size of the water heater needed, multiply the number of people in the household by the average time of each shower and the gallons of water used per minute by the showerhead. Then divide this result by the recovery rate of the water heater. This will give you the size of the water heater needed in gallons.

What is a Water Heater Size?

A water heater size refers to the capacity of a water heater to hold and heat a certain amount of water, typically measured in gallons in the United States. The size of the water heater you need depends on the number of people in your household and your peak water usage. Larger households or those with high hot water demand (such as multiple showers running simultaneously) will require a larger water heater. It’s important to choose the right size to ensure a sufficient supply of hot water without wasting energy on heating more water than needed.

How to Calculate Water Heater Size?

The following steps outline how to calculate the Water Heater Size.

  1. First, determine the number of people in the household (N).
  2. Next, determine the average time in minutes of each shower (T).
  3. Next, determine the gallons of water used per minute by the showerhead (G).
  4. Next, determine the recovery rate of the water heater (R).
  5. Finally, calculate the Water Heater Size (HS) using the formula HS = (N * T * G) / R.
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Number of people in the household (N) = 4

Average time in minutes of each shower (T) = 10

Gallons of water used per minute by the showerhead (G) = 2

Recovery rate of the water heater (R) = 40