How To Choose Tankless Water Heater[Buying Guide]🔥

When it comes to tankless water heaters, there are many conflicts we face. The most important fight is between the electric tankless water heaters and gas tankless water heaters. Don’t worry here I will tell you how to choose tankless water heater according to your need in the right way.

In this tankless water heater buying guide, I will discuss all the important factors like operation costs, installation costs, models, and also how to choose tankless water heater size step by step.

Let’s start with the difference between a traditional water heater and a tankless water heater then we will see a gas water heater vs an electric water heater.

Tankless Water Heater Buying Guide

Traditional Water Heater & Tankless Water Heater

The difference between a traditional water heater and a tankless water heater is, a traditional water heaters store the water in the tank and then heat that by using gas or electricity.

On the other hand, a tankless water heater heats the water as it is being used. That’s the advantage of tankless water heaters. It saves energy or electricity by not wasting it before water being used.

Gas Tankless Water Heater Vs Electric Tankless Water Heater

Gas Tankless Water HeaterElectric Tankless Water Heater
Installation PriceThe cost of the gas water heaters is costlier than the electric water heaters. Also, for gas water heaters you need to install a gas line and a ventilation line which increases the overall cost.In electric heaters, it is quite simpler than the gas water heater. It costs lesser and also doesn’t need any ventilation line or any other line.
Operational CostThe electric bill of the gas water heater is quite lesser than the electric water heaters of the same size.

For a gas water heater, it is gonna cost $200-$450 per year.
The electric bill of the electric water heater is quite higher than the gas water heaters of the same size.

For an electric water heater, it is gonna cost $280-$550 per year.
OutputThe gas-based tankless water heaters generally give more output than the electric tankless water heater. And that’s why they are been used in big buildings like apartments.The electric tankless water heaters can’t beat the gas tankless water heaters when it comes to output. Electric water heaters are good for only family purposes.

Condenser Water Heater VS Non-Condensing Water Heater

A condenser allows you to extract much more heat from the exhaust allowing for higher overall efficiency.Non-condensing gas heaters force-vent out the exhaust after heating the water within the coil.
They can deliver up to 98% of efficiencyThey can deliver up to 85% efficiency

There are these advantages to the condenser water heater is the exhaust comes much cooler than the non-condensing heaters. You can use the non-stainless steel venting pipes(which are cheaper).

Electric Heater Variations

There are 3 variants of electric water heater and they are whole house, point of use unit, and mini-tank units.

Whole housePoint of use unitMini tank units
As you understand from the name itself “whole house”, covers the whole house and has better functionality than point of use units. You don’t have to use many units of this, only one is enough for one house.Point of use units are more compact in size and you have to install them where ever you need the water like shower, dishwasher, kitchen, etc. They are small in size so fit in small spaces easily.

Its functionality isn’t better than whole-house heaters.
The mini-tank water heaters are also called hybrid water heaters. They are a hybrid of on-demand and traditional water tank heaters.

We can use them where we need a big amount of water with the highest pressure like in a shower. They have the tank where they store hot water and that’s y the water outlet pressure is more than other units.

How To Choose Tankless Water Heater Size?

When it comes to choosing the tankless water heaters, this is might be the biggest confusion, “which size of heater should I buy?”.

Buying extra big will cause wasting money and buying the smaller will cause cold showers. Before knowing how to choose tankless water heater size, we need to know two terms, GPM and Temperature rise. So, let’s understand them one by one.


GPM stands for Gallons Per Minute. This is the capacity that your heater can provide.

Temperature rise

Temperature rise is the difference between the ground water(normal water) temperature and the desired water temperature.

For example, the normal water temperature of your house is 50F and you want it to be 110F hot so that you can shower peacefully. So, 110-50=60 is the temperature rise here.

How to pick the right size tankless water heater?

The size of the tankless water heaters is measured in GPM. In order to know the right size heater for your needs, you need to find out the speed of your faucet.

Step1: Fill a 5 gallons bucket with the full speed from one of your faucets of outlets. Count the time it takes to fill fully in seconds.

Step2: Multiply the total time(in seconds) by 60. That will be the GPM of that outlet.

Step3: Now you got the GPM of one outlet and now you can add the all outlets you have in your house and pick the right tankless water heater in that GPM range.

Tub4.0 GPM102°F
Shower2.5 – 3.0 GPM104°F
Washing Machine2.0 GPM120°F
Dishwasher1.5 GPM110°F
Kitchen Sink1.5 GPM110°F

Now you have the GPM and temperature rise, with these you can choose the best tankless water heater for your house.

Tankless Water Heater Cost

As we know there are two types of tankless water heater, one is electric and another is the gas tankless water heater.

We discussed above that gas tankless water heaters are good for the whole apartment and electric ones are good for only family usages. So, gas water heaters give more output than electric ones.

Gas Tankless Water HeaterElectric Tankless Water Heater
Just because the gas water heater gives more output than electric water heaters, the cost of a gas water heater is more than an electric one.

The range of normal gas heaters is between $500 to $800.
As the electric water heater gives less output than gas water heaters, the cost of an electric water heater is less than a gas one.

The range of normal electric heaters is between $120 to $250.

Tankless Water Heater Lifespan

Usually, a tankless water heater lasts for more than 20 years without replacing or repairing it(if you buy a branded heater).

The electric tankless water heater like EcoSmart ECO provides you a lifetime warranty on electronics, exchangers, and elements.

And gas tankless water heaters like Rinnai says Guaranteed to Last: 10-, 5-, and 1-year residential factory warranty for heat exchanger, labor, and parts, respectively.

From these statements, you can understand how are they confident about their products’ durability. Once you buy a good water heater it can last for a lifetime, only you have to change the parts which doesn’t cost much.

Disadvantage Of Tankless Water Heater

Tankless water heaters don’t have a tank to store the water and heat it up, so they have to heat the water simultaneously while flowing thru the outlets. So, they have some limitations in speed. If many outlets are open then they may not heat the water at a constant temperature.

FAQ On Tankless Water Heater Buying Guide

Is it worth switching to a tankless water heater?

If you have traditional water heaters then it is better to switch to tankless heaters. Tankless water heaters are better than traditional water heaters because they are faster and efficient. Tankless ones use less energy also than traditional ones.


Here in this tankless water heater buying guide, I have discussed all the things you need to take care of while buying a tankless water heater.

The most important thing while buying a tankless water heater is, its GSM and Temperature rise, or else you won’t understand how to pick the right size tankless water heater.

The electric water heaters are good for family usage and gas water heaters are good for apartment usage.

I hope I have cleared your doubt about how to choose a tankless water heater for your house. If still, any doubt is there regarding tankless water heaters, comment down. Every feedback is appreciated.

I am Rajmun Khan from India, owner of Studying computer science and engineering. I have so much interest in home appliances and stuff. So, I learn them, implement them, and share the knowledge here.

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