Is it time to replace your water heater? If you’re looking for a cost-effective and efficient way to meet your hot water needs, you should go for a tankless water heater. 

As the name alludes, tankless water heaters do not have water tanks. They heat water on demand. This is energy-efficient as you only use energy to heat the exact amount of hot water you need. These systems also ensure that you never run out of hot water. 

However, this doesn’t mean that any size of tankless water heater will do. You’ll need to choose the right size of water heater to meet your needs. If you choose a tankless water heater that is too small, you won’t be able to use multiple appliances or bathrooms at the same time. 

The following are steps to follow to identify the right size of tankless water heater for your home. 

1. Assess your demand 

How many appliances do you have in your home? Do you have multiple bathrooms? The first step to sizing a tankless water heater is to determine the total flow rate of your appliances. For example, if your hot water faucet has a flow rate of 0.75 gallons per minute, your washing machine has a flow rate of 1 gallon per minute, your dish washer a flow rate of 1.5 gallons per minute and your shower head a flow rate of 2 gallons per minute, your total flow rate will be the sum of all these, which is 5.25 gallons per minute. 

If you want to be able to run all these appliances at the same time, you will need a tankless water heater with a total hot water flow rate of at least 5.25 gallons per minute. 

 

2. Determine the groundwater temperature 

The groundwater temperature is the temperature of the water running through your faucet before it is heated. For example, if you live in a cold area and the water running through your faucet is 50 degrees Fahrenheit before being heated, this is the groundwater temperature of your water. This value is important as the water heater must have the capacity to heat the water from this low temperature to your desired temperature. 

 

3. Determine your target water temperature 

What is your preferred water temperature? Do you love taking extremely hot showers or having comfortably warm baths? If you prefer to take a shower in water that is about 105 degrees, this will be your target temperature. You will need to invest in a water heater than can heat your water from 50 degrees to 105 degrees. This is a temperature rise of 55 degrees. You will therefore need to look for a tankless water system with a 55-degree Fahrenheit rise. 

With these two figures in mind, you can find a tankless water heater that is the right size for your household. You only need to find a system that matches these numbers. Use the numbers as the minimum rating for the system to ensure that you choose a system that will meet your needs even when you need more hot water, for instance, because you have installed more appliances that use hot water.