How does a Tankless Water Heater Work?

If you don’t want to risk running out of hot water just when you need it (while you’re showering while doing the dishes…), the best solution for you is to give tankless water heaters.

Tankless water heaters come with an added advantage and are also extremely energy efficient.

In fact, according to Air Group, tankless heaters can be 24%–34% more energy efficient than conventional storage tank water heaters.

But how do they work? And how are they never run out of hot water? In this article, we’re answering all your questions… so keep on reading if you want to find out how does a tankless water heater work.


What is a tankless water heater?

Before speaking about how it works, let’s try to define what a tankless water heater is.

Regular heaters work with a tank. Hot water is stored and kept hot in the tank, and when you need hot water in the shower, the kitchen, the bathroom, or anywhere, water comes from there. It is immediately hot, but – sooner or later – it runs out.

Tankless water heaters work differently: as their name suggests, they do not feature any tank. So how do they work?

Tankless water heaters are units that you can install anywhere you like. When needing water in your house, cold water enters the unit.

Inside the water heater, the water gets warmed so that it runs out of your faucets at the right temperature. 

You can easily understand how, with a system like this, you never run out of hot water: there is no limited amount of warmed water; there is your water system connected to a unit that can warm all the water that runs through it. 1

Read: 24+ Fascinating Heater Facts & Statistics

How do tankless water heaters Work?

So how does a tankless water heater work? Tankless water heaters are connected to your gas tubes.

Inside the unit, the gas feeds a small flame – or set of flames – that becomes responsible for heating the water.

So, inside the tankless water heaters, you have two entering tubes: one is for cold water, and the other for gas: this can become a piece of useful information when you need to understand where to install your tankless water heater in your house.

Here’s what Reddit users think

ELI5: How do tankless water heaters work?
by u/wangelalala in explainlikeimfive

The advantages of tankless water haters

Now that you’ve learned how they work, you can easily guess what are the advantages of tankless water heaters, especially when compared to regular hot water storage units.

  1. The main advantage is that you never run out of hot water;
  2. You can install the tankless water heater unit whenever you like in your house because it is a lot smaller than a big tank of hot water that should be able to supply the entire house;
  3. You can use a tankless water heater to provide for the entire house but also a single point of use.
  4. Tankless units only heat the water you use. On the contrary, hot water storage systems heat the water and reheat it constantly to keep it warm.

cons of Tankless water Heaters?

  • While with regular systems, you have hot water from your faucet as soon as you turn it open, with tankless water heaters, you may have to wait for some seconds before the hot water begins to flow.
  • Tankless water heaters entails risk of misuse. This is because if you miscalculate the desired flow rate of water then it can cause a lot of invconvinience for your home.
  • This type of water heater costs more than a conventional water heater, and the amount you save on energy is not that big of a number. 2

What are the Common Tankless Water Heater Problems & How to Fix Them?

Flow Rate of Tankless Water Heaters

The water usage in a Tankless water heater is calculated using gallons per minute (GPM), and it is very important to calculate this rate correctly.

For example, if you have under-calculated the GPM rate for dishwashing, then you will always run out of hot water and vice versa.

Here’s an ideal rate of GPM for different types of appliances.

ApplianceIdeal Flow Rate
Washing machine1.5-3.0 GPM
Shower1.0-2.0 GPM
Bathroom Faucets0.5-1.5 GPM
Dishwasher1.0-2.5 GPM
Kitchen Faucets1.0-2.5 GPM

Also Read: Pros And Cons Of A Tankless Water Heater?

Tankless Water Heater Buying Guide

Wrap Up

So tankless water heaters have their own advantages and have started gaining popularity.

They help save energy costs, but is it good enough to make one purchase them over conventional water heaters?

We will leave you to that question, as it is subjective to your household, number of family members, etc.

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What is the operating cost of tankless water heaters?

It costs less than $100 a year to operate a tankless water heater.

Which type of heater lasts longer, tank or tankless?

Estimates show tankless water heaters last longer- upto 20 years, while tank water heaters last for 10-15 years.

What is the installation cost of Tank water heaters?

The installation of a tankless water heater range from $4,500-$6,500, with an average of $5,500, inclusive of water heater cost, tune-ups, and warranty.

You will have to pay an additional $1800 and $3500 for its installation. 

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