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Best Under Sink Water Heaters of 2023

Under sink water heaters can save energy and provide instant hot water without needing to run the tap first.

Water heaters are expensive and you can easily overspend if you don’t choose wisely.

We’ve done extensive research on under sink water heaters to help you find your ideal heater in terms of price, quality, size, and many other factors.

To ensure you make the right decision and save some money, here are our best under sink water heater reviews.

Our Top Picks

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Product Comparison Table

Product Image of the Bosch Electric Mini-Tank Water Heater Tronic 3000 T 4-Gallon (ES4) - Eliminate Time for Hot Water - Shelf, Wall or Floor Mounted
Best for Low Hot Water Demands
Bosch Electric Mini-Tank
  • Made of glass-lined material
  • CFC-free foam insulation
  • Sleek design blends with decor
Product Image of the EcoSmart ECO 11 Electric Tankless Water Heater, 13KW at 240 Volts with Patented Self Modulating Technology
Best for Energy Efficiency
EcoSmart ECO 11
  • 99.8% energy efficient
  • Patented self-modulating technology
  • Digital display & thermostat
Product Image of the Thermoflow 2.5 Gallons 120 Volt Corded Electric Mini Tank Water Heater, Eliminate Time for Hot Water, Point of Use Water Heater,Plug in
Best for Colder Regions
Thermoflow UT10
  • Frost protection mode
  • EPS foaming heat system
  • Automatic thermostop function
Product Image of the Camplux ME25 Mini Tank Electric Water Heater 2.5-Gallon with Cord Plug,1.5kW at 120 Volts
Best for Outdoor Living
Camplux ME25
  • 2.5 gal glass-lined tank
  • Heat rate of 6.8 gal/hr
  • User-friendly thermostat with three modes
Product Image of the Bosch Electric Mini-Tank Water Heater Tronic 3000 T 7-Gallon (ES8) - Eliminate Time for Hot Water - Shelf, Wall or Floor Mounted
Best for High Hot Water Demands
Bosch ES8 Tronic
  • 7+ gallon water tank
  • Simple plug-in installation
  • 6-year warranty

Product Reviews

Here are 5 highly-regarded under sink water heaters to choose from.

1. Bosch Electric Mini-Tank Under Sink Water Heater

Best for Low Hot Water Demands

The Tronic 3000 T is a point-of-use mini-tank water heater available in three sizes, but we chose the 4-gallon tank. For those with lower hot water demands, such as a single sink far away from your other water heater, this is a good choice.

This under sink water heater is made with premium glass-lined material. It’s insulated with a layer of thick CFC-free foam, improving energy efficiency.

The compact size of this water heater means it fits perfectly under a sink. You can choose to simply mount it on the wall or a shelf using the included bracket. It has a sleek design that blends in with most decor.

It features a fitted thermostat where you can choose between “ideal,” “max,” and “min” settings.

Photo of the Bosch Electric Mini-Tank Under Sink Water Heater

What We Like

Perfect for Smaller Tasks

Thanks to its 4-gallon mini-tank, this water heater provides enough hot water for everyday small tasks, such as using a sink at the far end of your house.

Energy Efficient

Inside, it is lined with a thick layer of CFC-free foam, meaning the water heater wastes less energy. It uses minimal power, even on its highest setting.

Short Waiting Time

After you install it, it provides hot water almost instantly. It takes less than a minute to heat the water. When you close the faucet, it stores any leftover hot water.

What We Don't Like

Thermostat Is Too Simple

Some users complained that the thermostat is too simple. It can be difficult to know the exact temperature as the range is quite broad.

Can’t Place It Directly on the Floor

Although the manufacturer claims you can easily mount it on the floor, the bottom is curved. This means you will need a stabilizer underneath to prevent it from moving.

Product Specs

Tank volume 4 gallons
Voltage 120 V
Recovery rate 6.8 GPH
Temperature range 65 to 145 degrees Fahrenheit
Weight 17.4 pounds
Dimensions 13.75 inches by 13.75 inches by 13.5 inches

2. EcoSmart ECO 11 Tankless Under Sink Water Heater

Best for Energy Efficiency

The EcoSmart ECO 11 is a great tankless instant water heater if you want to reduce the load on your current water heating unit and save energy.

With this water heater, you could reduce the money spent on your water and electricity usage by as much as 50 percent. EcoSmart claims their tankless water heaters have a uniform energy factor of 0.98. This unit is a whopping 99.8 percent energy efficient.

EcoSmart’s range of tankless water heaters is designed using patented self-modulating technology. This allows each unit to regulate its energy output, ensuring optimal performance.

It is conveniently compact, yet very sleek in appearance. It features a thermostat and a digital screen displaying the exact temperature.

Photo of the EcoSmart ECO 11 Tankless Under Sink Water Heater

What We Like

Saves Loads of Energy

EcoSmart truly was eco-smart while creating this water heater. It is 99.8% energy efficient, producing hot water only when needed. It heats up almost instantly when called upon and turns off when not in use.

Small, Convenient Size

At around 11.5 inches by 8 inches, it is very lightweight, weighing only 6.5 pounds. You can mount it on almost any wall, but it’s best when close to the water source.

Digital Display and Thermostat

One of its most useful features is the digital display that shows exactly how hot the water is. The easy-to-use thermostat makes it even easier to operate. It’s smooth to adjust, adding a smart-tech feel.

Lifetime Warranty

Including a lifetime warranty is a definite plus. However, the warranty is limited in that it doesn’t cover any incidental damage.

What We Don't Like

Not for Higher Hot Water Demands

EcoSmart designed this model for smaller tasks. It works best when it’s close to the water outlet, such as a sink or shower. If there are multiple people using hot water simultaneously, the water will likely run cold.

Won’t Perform as Well in Colder Regions

EcoSmart warns that the water heater works best when external temperatures stay above 67 degrees Fahrenheit.

Product Specs

Tank volume Tankless
Voltage 240 V
Recovery rate 2 GPM
Temperature range 80 to 140 degrees Fahrenheit
Weight 6.5 pounds
Dimensions 11.5 inches by 8 inches by 3.75 inches

3. Thermoflow UT10 2.6-Gallon Mini-Tank Under Sink Water Heater

Best for Colder Regions

In colder regions, under sink water heaters are usually unsuitable. This model from Thermoflow might be the exception.

This is thanks to its frost protection mode, which activates as soon as the temperature drops too low. Still, avoid placing it where there’s a risk of freezing.

Its second mode is an energy-saving mode. The tank itself is made of stainless steel and lined with an EPS foaming heat system. This foam lining helps to heat the water more quickly, eliminating long waiting times while saving energy.

To save more energy, this instant water heater has a “thermostop” function. When the unit reaches the set temperature, it stops heating automatically until called on again.

Photo of the Thermoflow UT10 2.6-Gallon Mini-Tank Under Sink Water Heater

What We Like

Frost Protection Mode

This helpful feature means even those living up North can benefit from this heater. Under sink water heaters usually perform quite badly in cold weather but this seems to be the exception, thanks to German engineering!

Energy Efficiency

This heater works quickly and efficiently without wasting unnecessary energy. This is mostly thanks to its EPS foaming heat system and “thermostop” function.

Stainless-Steel Material

The tank is made from stainless steel, which means it’s quite resistant to rust and abrasion. Thermoflow even claims it doesn’t require any maintenance.

What We Don't Like

Installing Might Need Some Plumbing Expertise

Multiple users stated that it’s difficult to install and requires various wires and pipes. These are available in the U.S. but you might need to consult a plumber.

Product Specs

Tank volume 2.6 gallons
Voltage 120 V
Recovery rate 2.6 GPM
Temperature range 45 to 167 degrees Fahrenheit
Weight 14 pounds
Dimensions 18 inches by 12.2 inches by 11 inches

4. Camplux ME25 Electric Under Sink Water Heater

Best for Outdoor Living

Camplux provides a great solution for those who want to enjoy the great outdoors. This small under sink water heater should fit perfectly in any RV, boat, or even your patio kitchen station.

It has a 2.5 gallon, glass-lined water tank with extra insulation. This tank is all about efficiency, heating around 6.8 gallons per hour. It features an easy-to-use thermostat.

On the thermostat dial, you might notice a little snowflake graphic. When the heater isn’t in use for a prolonged period, particularly during winter, turn the dial to the snowflake. This is a freeze-protection setting to prevent any remaining water from freezing.

Another helpful feature is overheating protection, which provides extra assurance that you and your family are safe.

Photo of the Camplux ME25 Electric Under Sink Water Heater

What We Like

Easy-To-Use Thermostat

The thermostat is straightforward to use. Simply turn it to high, medium, or low and it will take care of the rest.

Freeze Protection

If you install this unit in your RV or boat, this feature is essential. You’re less likely to spend the winter in your RV or boat, so this will keep it protected when not in use.

Overheat Protection

On the other hand, you will also have some assurance that it won’t cause a fire. The overheat protection prevents the unit from overheating.

What We Don't Like

Stated Dimensions Are Misleading

Some users pointed out that when measuring to see if this can fit in a cabinet or under a kitchen sink, you need to add at least 4 inches. This is due to the required pipes.

Product Specs

Tank volume 2.5 gallons
Voltage 120 V
Recovery rate 6.8 GPH
Temperature range 77 to 140 degrees Fahrenheit
Weight 20 pounds
Dimensions 17.25 inches by 11.75 inches by 10.38 inches

5. Bosch Electric ‎ES8 Tronic 3000 Water Under Sink Water Heater

Best for High Hot Water Demands

Bosch is one of our favorite brands, and this is one of their larger under sink water heaters. It provides enough hot water for a large family. This is perfect if your water always runs cold before mom gets to finish her shower.

This Bosch water heater features a 7+ gallon water tank. It’s quite large, measuring ‎17.5 inches by 17.5 inches by 14.5 inches, and weighs approximately 30 pounds.

It is also very easy to install. Simply place it under your sink, connect the water pipes, and plug it into a standard outlet. Like our other example from Bosch, this also has a glass-lined tank.

Photo of the Bosch Electric ‎ES8 Tronic 3000 Water Under Sink Water Heater

What We Like

Works Perfectly for Higher Hot Water Consumption

This Bosch under sink water heater is perfect for anyone needing extra hot water. It has a large 7-gallon mini-tank that will store the hot water until you need it.

Easy to Install

The installation is relatively straightforward. You don’t need any hard wiring; simply connect it to the water source and plug it in.

6-Year Warranty

With an excellent under sink water heater, you will also receive a 6-year warranty.

What We Don't Like

Takes a Little Longer to Heat Up

A few users pointed out that its recovery time was a little longer than its competitors. This might be due to its larger water tank. It takes about 10 minutes to heat up.

Product Specs

Tank volume 7+ gallons
Voltage 120 V
Recovery rate 6.8 GPH
Temperature range 65 to 145 degrees Fahrenheit
Weight 29.5 pounds
Dimensions 17.5 inches by 17.5 inches by 14.5 inches

Product Comparison Chart

Product Award Volume Voltage Recovery Rate Temp Range Weight Dimensions
Bosch Electric Mini-Tank Low Hot Water Demands 4 gal 120 V 6.8 GPH 65 – 145 F 17.4 lbs 13.75″ x 13.75″ x 13.5″
EcoSmart ECO Energy Efficiency N/A 240 V 2 GPH 80 – 140 F 6.5 lbs 11.5″ x 8″ x 3.75″
Thermoflow UT10 Colder Regions 2.6 gal 120 V 2.6 GPH 45 – 167 F 14 lbs 18″ x 12.2″ x 11″
Camplux ME25 Outdoor Living 2.5 gal 120 V 6.9 GPH 77 – 140 F 20 lbs 17.25″ x 11.75″ x 10.38″
Bosch Tronic ES8 High Hot Water Demands 7+ gal 120 V 6.8 GPH 65 – 145 F 29.5 lbs 17.5″ x 17.5″ x 14.5″

Why Buy an Under Sink Water Heater?

An under sink water heater is not intended to replace your current, larger heater. Instead, it provides you with some extra hot water for the last few dishes.

Under sink water heaters are designed to provide sufficient hot water for smaller tasks. This could be for your kitchen faucet or for extra water to your shower. They help you save the money that would otherwise be wasted on keeping your larger main water heater going.

These water heaters are small electrical appliances that you can install almost anywhere. Someone might install one in their boat, RV, cottage, apartment, office, or garage.

You might also know them as “under counter”, “under cabinet” or “instant” water heaters. Some of the main advantages of these appliances are that they save water, energy, and space.

Keep In Mind

Under sink water heaters are not replacements for your larger heater. Either connect them directly to your sink or shower or use them in line with your current unit.

Let’s look at some more benefits of under sink water heaters.

  • Fast and efficient: The average under sink tankless water heater will supply hot water almost instantly. A tank-type heater will take a couple of minutes.
  • Reduced environmental impact: With a hot water “on-demand” system, you will reduce your negative impact on the environment.
  • Compact size: As an under counter water heater is small and compact, you can place it in most cabinets or beneath your sink.
  • Easy to install: Thanks to its compact size, the installation cost is less. If you’re handy, you can likely do it yourself.
  • Cleaner water: Under sink water heaters have more of a “point-delivery system.” There is less chance of contamination, which often affects larger units (1).

Types of Under Sink Water Heaters

In general, there are two types of under sink water heaters: tank-type and tankless type. Both have pros and cons, so let’s take a closer look at both.

Tankless Water Heater

An under sink tankless water heater is the smallest heater you’ll encounter. The average length is about the same as an average laptop.

They heat the water without using a storage tank. As soon as you open the hot water tap, warm water will stream out until you turn it back off.

As no large tank is needed, these are very easy to fit under the sink or wherever else you need one. They are also the most cost-efficient, as they don’t require much energy or water. They often also include a turning dial or remote control to set the right temperature.

However, they’re not the best choice if your hot water demands are high, such as if you have a large family (2). Performing several demanding tasks at the same time can be too much for the tankless water heater.


  • Instant hot water. Powerful GPM (gallons per minute).
  • Economical energy cost.
  • Small, compact size. Easy to install.
  • Requires less maintenance.


  • Generally pricier than tank-type instant water heaters.
  • Not suitable for people with higher water needs.

Tank Water Heater

Tank water heaters are an affordable option, as they cost less and use less water. They usually include a mini tank that can hold 2 to 2.5 gallons of water. Some have larger tanks, ranging up to 7 gallons.

Similar to the tankless type, tank heaters are also straightforward to install. Most can be mounted on the wall, under your sink, or directly onto the floor. However, you will need some extra space for the mini tank.

These are a great choice if you own an RV, boat, or small apartment. Although it uses a tank, you won’t need to install extra pipes around your house. Simply install it wherever you need it.


  • Most affordable choice.
  • On-demand hot water.
  • Works well even if you have larger water needs.
  • Provides sufficient hot water for smaller tasks such as washing hands or cleaning a few dishes.


  • Requires more time to heat the water, not insta-hot.
  • Needs regular maintenance.
  • Demands more space.

How to Choose (Buying Guide)

There are a couple of things to consider before buying an under sink water heater. It mainly depends on your water usage and where you need it the most.


Water heater size is perhaps the most important factor to consider. Many people opt for under sink water heaters because they have less space available.

Water heaters with tanks occupy more space than tankless heaters, though still less than your regular heater. Carefully consider the area where you want the unit to be placed and decide accordingly.


Some instant electric water heaters have high electricity demands. You need to be confident that your power circuit at home can cope with the extra strain.

How many volts the instant heater needs depends on the model. Some require around 120V, while others need 240V.

Hot Water Demand

Calculating approximately how much hot water you need per minute will help you make an informed decision.

Every under sink heater has a fixed flow per minute of hot water. It’s estimated that the average American uses around 2.1 gallons of water per minute during an 8.2-minute shower (3). However, it might be as little as 1 gallon or more than 2.5 gallons.

Your Location

The temperature of the local water supply differs depending on where you live. Temperatures are generally warmer down South than they are up North. This means that if you live in Texas, you are unlikely to need a water heater as powerful as someone living in Alaska.

Making the right choice here could save you some money. Choosing a powerful water heater when your inlet water is already warm could increase your electricity bill unnecessarily.

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What is an Under Sink Water Heater?

An under sink water heater is a type of heater that has been designed to fit into spaces that would be too small for traditional tank heaters. They can be placed under sinks and their close proximity means they provide hot water almost instantly when the hot tap is turned on.

Can You Put a Tankless Water Heater Under a Sink?

As their name suggests, tankless water heaters don’t require a tank. This reduces their overall size and means most tankless heaters will fit under the majority of kitchen sinks. As with any type of appliance, it depends on its specific size and how much space you have to work with. Measure the area under your sink and keep in mind that you will need to fit the heater and any necessary pipes and wiring.

Are Under Sink Water Heaters Worth It?

Yes, many people believe that under sink water heaters are worthy due to their efficiency. Since they tend to consume less energy than traditional heaters, they reduce energy consumption throughout the household.

They require less energy to heat water, and they also don’t need a lot of energy to keep too much water at a higher temperature.

How Reliable Are Under the Sink Water Heaters?

Under the sink water heaters can be very reliable if you know what to look for when purchasing such a product.

They are reliable to those looking for a solution to heat water real quick, for a unit that offers an endless supply of hot water, and for those looking for a small and energy-efficient unit.

They are stylish, discreet, and easy to install and maintain. However, water leaks are less noticeable, and the water temperature is sometimes tricky to adjust.

How Do You Install an Instant Hot Water Heater Under the Sink?

To install an instant water heater under the sink, you first have to ensure that there are 12 inches of open space around it.

You’ll have to set up the mounting brackets, turn off the water supply but the cold water supply line, and install some Y fittings. After making all the water supply connections, you also need to turn off the power to run the electrical lines needed to power the heater from the electrical panel.

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Headshot of Peter Gray

About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.