Tankless Water Heaters for The Bathroom: Pros And Cons

rainfall showerhead

Putting a tankless water heater in your house to supply the bathrooms and all your water needs can be a great idea. These units are designed to provide hot water on-demand. At about a tenth the size of a traditional unit, they not only reduce clutter but also are great for the environment.

Installing a tankless water heater supplies instant hot water to your bathroom and entire home on-demand. Initial costs are more expensive than traditional storage systems, but a tankless water heater is more energy efficient in the long run. 

I spoke to Bob Lemons, the owner and operator of Mr. Tankless. He dominates the tankless water heater installation market in Central Texas, installing more than 300 every year. His career in tankless all started 20 years ago when the Bosch company invited a thousand plumbers in the area to an event to learn about the new tankless revolution.

Guess who was the only one who showed up? Mr. Tankless!

Read on to get Bob’s expert advice about whether a tankless water heater can provide the best option for you. Plus, don’t miss his critical words of wisdom regarding installation and how to save big money.


Is a Tankless Water Heater Good for a Bathroom?


Most of us know of and are familiar with how a traditional boiler storage system works, so why would we change to a tankless water heater, especially for a bathroom that needs to supply lots of hot water, often to a few faucets at the same time?

No matter the size of the space or how many people will be using the bathroom, an instant tankless water heater will always supply the amount of hot water needed on-demand.

There are many benefits to fitting a tankless water heater in a bathroom:

  • They are cheaper to operate as they don’t have to store the water to keep it warm
  • They have a longer life-span than a traditional boiler-style heater
  • Water is always hot on-demand; no matter how many people are waiting to use the shower, there will always be enough hot water!
  • There’s no risk of water damage from traditional boiler-style storage heaters!
  • Clutter-free!

Mr. Tankless puts it like this:

“Tankless is the way to go if you have multiple shower heads or garden tubs that you can’t fill. If you try to fill a 60-gallon jacuzzi tub, you’d get a quarter of the way before you start running out of hot water. With tankless, you can fill a large tub and enjoy a nice bath. You’re not ever going to run out of hot water.”

He says usually the tankless water heaters are used to supply the entire home, including the bathrooms.

Essential for Energy-Efficient Bathrooms

With so many people becoming increasingly concerned about climate change, more people want to operate energy-efficient homes. And the bathroom is a key spot in the home where energy is consumed. The tankless water heater is essential to create the most energy-efficient bathroom possible. But exactly how eco-friendly are they?

According to the US Department of Energy:

“For homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters. They can be 8%–14% more energy efficient for homes that use a lot of hot water — around 86 gallons per day.”

Other ways to save water in the bathroom include reusing bath water to do laundry or water your garden. If you love our planet, read my post 16 Tips to Make a Bathroom Energy Efficient (& Save Money!).  Implementing many of these tips won’t cost you a cent and could save you quite a bit.


How Do Tankless Water Heaters Work?

In most homes, a standard boiler tank is the traditional storage unit of choice for storing water and keeping it hot until the water is needed. Generally, electricity, natural gas, or propane are used to power the element inside the boiler and keep the water hot.

A boiler storage tank can safely store from 30 to 60 gallons (136 to 272 liters) of water at any one time. It uses an enormous amount of power to keep the water at a constant temperature. Then, as the water is emptied from the boiler, fresh water is pumped in using more power to heat the fresh water to reach the correct temperature.

A tankless water heater provides on-demand hot water. This means that whenever you need hot water and open a faucet, cold, fresh water enters the tankless unit. Next, the burner is activated and the water is heated to the correct temperature as it passes through the burner. Finally, you receive the hot water from your faucet or outlet pipe, almost instantly!

The heating unit automatically turns off when you switch off your faucet. This system effectively eliminates the need for massive, unsightly storage tanks and also cuts down on operating costs while using less energy.


Types of Tankless Water Heaters

There are a wide range of tankless water heaters available. These include mini heaters, compact heaters, and even comfort heaters. This means there is a unit suited for your needs at a price that you can afford. 

Tankless water heaters are powered either by electricity or gas. The electric models are more popular than the gas models as they last longer, are typically smaller units, and are easier to install. 

Let’s briefly discuss the two options.


1. Gas-Powered Tankless Water Heaters

Gas-powered tankless water heaters produce a higher water flow rate (gallons or liters used per minute) than electric models. For example, a gas-powered water heater can heat up to 5 gallons (22 liters) of water to 70 degrees Fahrenheit (21 degrees Celsius) in one minute. A gas-powered water heater is an excellent option for larger homes that use a lot of water. 

However, they are substantially more expensive than their electric counterparts and need to be installed by a professional. In addition, these models require good ventilation. 

Gas-powered water heaters also need an annual maintenance check to keep them in good condition, but they have a potential life span of around 20 years or more, so they are worth the upkeep!

The Rinnai Tankless Hot Water Heaters run on natural gas or propane, and can provide 5.3-9.8 gallons per minute, depending on the model you select. You do need to purchase a special vent pipe for these units. Though you invest upfront, you can recoup and then some when paying your water bill. 

Mr. Tankless says the longevity of a gas-powered tankless water heater is much longer than that of an electric-powered tankless heater. Plus, he says, you’ll save up to 50% on your monthly gas bill.

Mr. Tankless recommends Rinnai gas-powered models. “The Rinnai has been around the longest. They have great warranties. And the unit is solid,” he tells me.

Learn more about Rinnai models on Amazon.


2. Electric-Powered Tankless Water Heaters

Electric-powered tankless water heaters are cheaper to install than gas models and you can safely place them anywhere in your home—including the bathroom!— since they do not require ventilation. 

Once you have determined the required flow rate for your needs, you can typically choose a water heater without worrying about overpriced installation costs. An electric-powered water heater can heat up to 2 gallons (9 liters) of water to 70 degrees Fahrenheit (21 degrees Celsius) in one minute.

Electric-powered water heater units are not only much cheaper than gas heaters, but they also don’t require much maintenance and have a life expectancy of twice that of a traditional boiler storage tank!

For example, let’s look at the Ecosmart ECO 18 Electric Tankless Water Heater. Weighing in at only 14 pounds, it’s 90% smaller than a traditional water tank. Plus, it can be wall-mounted to save space and can heat from 1.8 to 4.3 gallons-per-minute. This can provide on-demand, endless hot water to your bathroom, while saving you up to 50% on your monthly water heating costs.

Click here to see the ECO 18 on Amazon.


Where to Install a Tankless Water Heater

When installing a tankless water heater, the only restriction is to leave access to the unit for maintenance purposes. Other than that, you can install a tankless water heater wherever you want it in your home or even outdoors.

You can even use the original hookups from the previous tank to save costs. And if you install a gas-powered unit, make sure that you have the correct dedicated connections and plenty of ventilation.

Installing the unit in the bathroom can maximize the water temperature and flow as the distance from the faucets to the water heater is shorter.  

Points to consider before installation are:

  • The distance to the water heater from the outlet pipe. If you install the unit in the basement and your bathroom is on the second floor, you might experience a delay in hot water reaching the faucet.
  • The distance from the water to anything combustible. Allow at least 24 inches for safety.
  • The safety regulations in your state or city. Discuss options with your plumber before deciding on a location.


What Size Is Good for One Bathroom?

When you choose the size of the tankless water heater you want, consider how many baths, showers, basins, and toilets will be used at any one time. Next, work out how many gallons of water per minute (the flow rate) you need to supply each faucet and outlet. Then look for a tankless water heater to provide the combined flow rate.

Tankless water heaters come in different sizes, so you might supplement a traditional water boiler by putting a tankless unit in each bathroom. This will ensure a good water flow to each tub and faucet.

The RX-13 Residential Tankless Water Heater by Rheem is the perfect size for on-demand hot water for a single bathroom, RV or apartment. See it here on Amazon.

Purchase the size of the water heater that will meet the demand. For example, a household with two occupants would only use a flow rate of 30 gallons (136 liters), whereas a home with five occupants could require 80+ gallons (363 liters) per use. According to Mr. Tankless, most bathtubs require 3-7 gallons per minute.

Follow this quick guide to determine the size of the tankless water heater that you need for your bathroom:

  1. How big is your house and how many rooms use water? Although water heaters do vary in size, modern units are strong enough to supply your entire home if you install one large enough for the job. 
  2. Determine how many faucets and outlets you need to run and their flow rate requirements. How many faucets you tend to run simultaneously should determine the size of your water heater, as the flow should be able to support the number of running faucets.
  3. What is the required temperature per faucet? The water heater should generate enough heat to supply the required heat to each faucet. 
  4. What is the water demand during peak usage times in your household? The water heater should be able to meet the requirements at your home’s busiest moments.
  5. Consider your budget and buy the biggest water heater that you can afford.


Buying a Tankless Water Heater

Before purchasing a tankless water heater for your space, research which type of heater, either gas or electric, would be best for you. Consider which power source you have. If you choose to purchase a gas water heater, make sure you have adequate ventilation as well as a connection to the room where you plan to house the heater.

Here is an excellent video from ecosmart gives you a good idea of the various factors that will impact your choice of tankless water heater:



  • Determine the correct size of the water heater that you will need by calculating the required flow rate and the space that you have available. 
  • Consider the climate in your area. For example, if you live in a colder climate, you could experience frozen pipes, affecting the water flow to the heating unit. If the water freezes inside your water heater, the warranty won’t cover it, so you’ll need to contact the manufacturer before trying to repair it. On the other hand, if you live in a warmer climate, you could install the water heater outside if you don’t have enough space indoors. 
  • Consider the warranty of the water heater. Some units have a ten-year warranty, while others cost as much to repair as it would buy a new unit.

Pros and Cons of Tankless Water Heaters

When comparing water heaters and deciding which one to install in your home, consider the benefits and drawbacks of each model. These are a few of the top advantages and disadvantages of tankless water heaters.

Pros of tankless water heaters:

  • Most tankless water heaters have a potential life expectancy of 5-20 years or more which is substantially longer than traditional tank-based systems.
  • As there is no bulky water storage tank, they are compact and can fit in any space, making them convenient and easy to install.
  • Instant hot water at a rate of 2 to 3 gallons (9 to 13 liters) per minute means that you don’t waste water while waiting for the hot water to flow through.
  • Tankless water heaters are more energy-efficient and only heat the water when you need it.
  • The constant temperature can be adjusted during different seasons, allowing for better energy consumption during the warmer months.
  • A tankless water heater will take up a lot less space in your bathroom than a traditional storage tank.
  • There are fewer chances of leaking water from unseen damages as the length of pipes to the faucet or outlet is shorter.
  • No chance of bursting storage tanks causing water damage in your home.
  • An intelligent investment when renovating or building a new property, adding value to your property.
  • Some water heaters are Wi-Fi capable and can be monitored and controlled by your smartphone.
  • Ideal for use in warmer and colder climates alike.

Cons of tankless water heaters:

  • A tankless water heater system is initially more expensive than traditional water boiler- systems.
  • You may need extensive renovations to accommodate the water heater system if the connections are only available for traditional water storage systems.
  • If your household water usage is high, a larger unit or even more than one unit may be required for your household use.
  • Smaller units should be flushed with vinegar every three weeks to keep sediments from clogging the heat exchanger.
  • As this system is tankless and does not have a water storage tank,  it cannot provide hot water during power outages. Even gas-powered tankless water heaters will not work in a freeze.
  • The hot water temperature can be inconsistent when multiple outlets are in use simultaneously.

Mr. Tankless Tells All! Installation and Rebates

Here we get some very wise words from Mr. Tankless:

First, get a certified tankless installer to do your work. Not just any plumber off the street. Why? Because these units can easily get messed up by someone who doesn’t know what they’re doing. And worse, if you don’t use a certified tankless installer, then you void the warranty. Mr. Tankless says:

“The manufacturers are very strict about who puts the product in. Installed correctly, these things are jewels.”

Second, check with your city about rebates. Because the tankless water heaters are energy-efficient, many cities offer you an incentive to install one. In Austin, Texas, for example, the city currently offers a $650 rebate. On top of this, the US federal government offers a $300 tax credit. And on top of that, many manufacturers provide their own rebates. So spend an hour looking into this—it will pay off!



Is a Tankless Water Heater Worth It?

If you are currently using a boiler-style storage system to heat your water, then read on! Here is our comparison list of the advantages and disadvantages of boiler-style systems compared to tankless water heaters. I used the electric water heater in the comparison.

 TanklessStorage Tank
How They WorkOn-demand water not stored in tankWater stored in 30-60 gallon tanks
Price and Installation CostUnits are expensive and installation costs moreLess expensive; Easy DIY installation
PerformanceProvides a constant supply of hot water at 120 degrees Fahrenheit (48 degrees Celsius)Gives a steady supply of hot water at 120 degrees Fahrenheit (48 degrees Celsius)
Operating CostsAnnual operating costs average $535.00
Annual operating costs average $580.00
Energy EfficiencyExcellentGood
MaintenanceOnce a yearUnder warranty for 15 years
Size of UnitSmall and compactBig and bulky
LocationAny space if connections are supplied, indoors or outdoorsOnly where size allows


Tankless Water Heater for the Bathroom?

Tankless water heaters are not for everyone. They require more upfront investment while providing cost savings in the long run. And because they don’t routinely heat all the water in a traditional tank, they are the most energy-efficient solution on the market. But if you want an energy-efficient bathroom, this is the way to go.

Be sure to choose the right water heater based on the demand and flow rate needed for your bathrooms, as well as the climate in your area. And finally, unless you are quite handy yourself, you would be wise to have a qualified professional install your tankless unit.


Shana Burg is a bath enthusiast, content strategist, and award-winning writer. She is the founder of bathtubber.com.

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