Top 7 Under Sink Water Heater Reviews (Updated 2023)

Mother and her daughter washing vegetables with a water heater under the sink

[vc_row][vc_column][vc_column_text]Close-up of a residential hot water heaterDid you notice a strange leak coming from the heater under your sink? Maybe you’re remodeling your kitchen and don’t know which heater to get? No matter what the reason is, I’m here to help you find the best water heater for your home.

In my sink tankless water heater, I’m going to show you my top 7 choices and talk about some of their features. What’s more, I’m going to tell you what to look for when buying a heater.

Not only that, but I’m also going to show you what it takes to install a heater and how to do it yourself. By the time you finish reading this review, you’ll be a pro at choosing and setting up tankless electric water heaters.

But, that’s not all. At the end of my under a sink water heater, I’m also going to share with you my top choice for the best under sink water heater on the market. If you want to learn more about water heaters and others like a power vent water heater on how to use them — stay tuned.[/vc_column_text][wpsm_titlebox title=”” style=”3″]

My Top Picks

Now, let’s get into the under sink water heater and talk about the benefits and features of each model. I’m also going to show you which water heater takes the number one spot in the end.

1. Bosch Tronic 3000 T

Bosch Tronic 3000 T

First up, we have a water heater from Bosch, a well-known and respected company. While Bosch has a huge selection of water heaters, for me, this model stands out from the crowd, and it’s one of their bestsellers.

Features and Benefits

The Tronic 3000 T is a mini-tank, point-of-use electric heater that features a modern and sleek design. It comes in three different sizes, and you can get the 2.5, 5, and 7-gallon heater. What’s more, you can use it as your primary heating source or as a booster for your main heater.

It has a knob to control the temperature and an LED display. The temperature range for this model is 65–145°F. Bosch has also included pressure and temperature relief valves in the kit.

If you go for this heater, Bosch will give you a 6-year limited warranty on the unit. Also, you’ll get a 2-year warranty for parts. It has a couple of applications, and you can put it under your sink.

Moreover, you can use it in in-law suites, smaller apartments, and kitchenettes. The heater also has a maximum operating pressure of 150 GPM, and the thermal efficiency for this model is 98%.


Installing the Bosch Tronic is pretty simple, and you can mount it to your wall or put in on a shelf. I’m going to use the next part of my under sink water heater to talk a bit more about how to install it yourself.

First, you need to tap into your cold water line and provide an electrical connection. As I mentioned, you can use this heater by itself to provide a small volume of water to your sink. But, you can also install it in line with a central water heater near your point-of-use. By doing so, you won’t have to wait for hot water when you open your faucet.

Of course, before you start installing the heater, make sure to first check with your owner’s manual. Finally, before you connect the Tronic 3000 T to a power supply, fill it with water and purge all of the air from the system.

One thing to note about this heater is that, if you don’t install it properly, you could have a problem with the thermostat. If you don’t follow the owner’s manual to the letter, your thermostat might act up and show the wrong temperature.

2. EcoSmart ECO 11

EcoSmart ECO 11

The next model I wanted to feature in my under sink water heater is the ECO 11. Let’s take a look at how this model compares to the one from Bosch.

Features and Benefits

The ECO 11 is one of EcoSmart’s more popular models, and it could supply hot water to multiple faucets in colder climates. You could put it under the sink in your bathroom or office and have a good hot supply.

On the other hand, in warmer climates, you could use this heater to supply hot water to a shower or multiple appliances. The ECO 11 comes with a digital display, and you can adjust the temperature in 1°F increments.

What’s more, it has EcoSmart’s patented self-modulating technology. With this technology, the heater will regulate the energy output on its own, ensuring optimal heating. Also, the ECO 11 can heat up two gallons of water per minute, making it a great choice for larger households. The temperature range for this model is 67–105°F.

Another interesting feature about this heater is that it comes with a lifetime limited warranty. The warranty covers the exchange, electronics, and the elements. Keep in mind that it won’t cover labor costs or accidental damages.


Similar to the model from Bosch, the ECO 11 is pretty easy install. You’re going to need a couple of tools and your owner’s manual. If you need some visual help, EcoSmart has an instructional video on YouTube to help you install your heater.

What’s more, EcoSmart recommends only using this heater indoors. But, if you want to put it outside, just make sure it’s protected from the elements.

Also, before buying the heater, make sure to check how it would fit your needs and household. You can take a look at their sizing chart to see how much you can get out of this heater in your climate.

Finally, make sure to do proper maintenance and clean the heater at least once a year. While the lifetime warranty is a good thing to have, it doesn’t cover sediment or limescale buildup.

3. EcoSmart ECO MINI


Since EcoSmart is such a popular brand, I wanted to feature another one of their products in my under sink water heater. Now, let’s talk about some of the similarities and differences between these two units.

Features and Benefits

First, we have to talk about sizes since there are four different ones you can get. You can get the ECO Mini 1, 2.5, 4, and 6. The numbers represent the gallons that fit in one of these water heaters.

Even though they all come in different sizes, the heaters are still small enough to fit under your sink or in your bathroom. What’s more, EcoSmart claims the entire Mini line has an efficiency rate of 99.8% and no standby loss.

Except for the ECO Mini 6, all of the other heaters in the line are pretty easy install and come with an included appliance cord. However, the Mini with a 6-gallon tank needs to be hardwired. I’ll talk a bit more about the process a little later in my under sink water heater.

Also, keep in mind that each of these models has a different recovery time once they’re drained. If you want to learn more about that, you can check out the spec sheet for the Eco Mini.

One thing where the Mini differs from the ECO 11 model is the warranty. With the ECO Mini series, you only get a 5-year limited warranty for leaks and 2 years for parts.


Now, as I previously mentioned, the ECO Mini 6 needs to be hardwired. I would recommend installing the model 6 only if you have some previous experience with water heater installation.

If you don’t, I recommend calling a contractor because EcoSmart’s warranty becomes void if the heater isn’t properly installed. Of course, you should check with your owner’s manual before you start the process.

Another thing to note about these heaters is that they can develop limescale buildup. If you’re not sure how to clean your heater, you can check out this instructional video for more details.

4. Rheem 240V RTEX-13

Rheem 240V RTEX-13

Another company I wanted to include in my under sink water heater is Rheem. They are famous for their HVAC products, and the RTEX-13 model is one of the best tankless heaters in the market.

Features and Benefits

The heater from Rheem is a tankless water heater that delivers hot water on-demand. Similar to the ECO Mini line, the RTEX-13 comes in three different sizes. Depending on the size of your household and your needs, you can get the 8kW, 11kW, and 13kW model.

The 8kW could be a good fit if you live in a smaller house or apartment. It has lower water pressure, so you might not be able to power multiple appliances at the same time. On the other hand, with the 13kW heater, Rheem claims you get an endless supply of hot water.

The heater also has self-modulating technology and digital display so you can control the temperature. What’s more, it features robust copper heating elements. They are also threaded and can be easily replaced. When it comes to warranty, Rheem offers a 5-year primary one.

If you’re not sure which size to get, Rheem has a great feature on their website. When you input your region and what you want to use the heater for, it’ll give you a list of recommendations.


The Rheem RTEX-13 is pretty easy install, and it comes with the necessary equipment. It should go without saying, but always check your owner’s manual before you start installing it. The manual will not only tell you how to install your heater but also how to take care of it.

Since it’s made of copper and brass, the water heater can easily develop a limescale buildup or even rust. Rheem recommends doing a check-up once a year to ensure there isn’t any damage or leaks.

Keep in mind that the 8kW is only for smaller water applications. If you open more than one faucet at the same time, you risk running out of hot water. I recommend buying the Rheem RTEX-13 for smaller households, offices or apartments.

5. Bosch Ariston GL4S

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Next up is another water heater from Bosch. The reason why I wanted to include the GL4S in my under sink water heater is that I think it could be a good choice for any home, big or small.

Features and Benefits

The Ariston is a mini-tank water heater with a compact design, perfect for installing under the sink. This model is a 4-gallon heater that can supply multiple faucets with hot water at the same time.

You can use it on its own or as a booster for your main heater. The Ariston could work great if you need it for shorter draws of hot water or you want to hook it up to your dishwasher.

However, I wouldn’t recommend installing it in your bathroom and trying to power a shower head with it. Since it is so small, it won’t give you the hot supply you need for a nice, long shower.

The heater has a glass lining to prevent leaks and corrosion. What’s more, it has a thermostat and a dial to ensure you choose the temperature that’s perfect for you. Keep in mind that the Ariston is for indoor use only.

If you want to install it outside, make sure it’s protected from sun exposure or weather conditions. With that said, I think it could be a good fit if you want to install it in your RV or camper.


While the installation process is pretty simple, I wanted to go into the details a bit more in my under sink water heater. First, the heater comes with all the necessary equipment you need to install it.

Also, it comes with a pressure-relief valve that you can use to set the temperature just the way you like it. The heater doesn’t need any hardwiring; in fact, all you need is a 15A outlet, and you’re set. If you’ve never installed a water heater before, you can check out this video to find more detailed instructions.

One thing to keep in mind with the Ariston is that it shares a similar problem as the Bosch Tronic 3000. Since the thermostat is hidden behind three layers of insulation panels, you might get an inaccurate reading sometimes.

6. Thermoflow UT10

Thermoflow UT10

Now, let’s talk about a heater from Thermoflow. In my opinion, Thermoflow’s heater is an underrated product, which is why I wanted to include it in my under sink water heater.

Features and Benefits

The UT10 is a steel mini-tank water heater. It is a 2.6-gallon heater that would be good for smaller water applications. What’s more, all of the elements in the heater are made out of steel, which makes them easy to replace.

Now, Thermoflow has the Thermostop feature which is supposed to ensure a fast recovery time. Once the water in the heater matches the temperature you’ve set, it will stop heating. By doing so, it saves energy, and you won’t experience any standby loss.

Another reason why I wanted to include UT10 in my under sink water heater is that you can install it indoors and outdoors. It has overheating protection, and it is waterproof. Of course, if you plan on installing outside, make sure you put it in some sort of enclosure to avoid damaging it.

Also, it has EPS foaming technology and a safety feature. If there’s a problem with the heater and it doesn’t deliver hot water, it will immediately shut off the electric supply to prevent it from overheating.

The temperature range for this model is 45–165°F. What’s more, with the EPS technology, the heater is able to deliver hot water to your sink much faster. It also comes with a 2-year limited warranty.


The UT10 is pretty great, and it will only take you a couple of hours to do it yourself. First, tap into your cold water line and install directly under your sink. Then, plug it into a 120V electric supply socket, and you’re done.

Keep in mind that you’ll get the instruction manual and brass bushings when you order the heater. But, the water heater hose and pedestal aren’t included. Finally, since it is a steel heater, make sure to do proper maintenance at least once a year to avoid limescale buildup.

7. Stiebel Eltron 233219

Stiebel Eltron 233219

Last but not least, I wanted to feature a model from Stiebel Eltron in my under sink water heater. Let’s take a look at how this water heater compares to the others we’ve talked about.

Features and Benefits

The Stiebel Eltron unit is a glass-lined tank which comes as 2.5, 4, and 6-gallon DHC model. The heater is small enough for you to put it under your sink but big enough to give you a good hot supply.

You can use it as a booster for your main heater or on its own. What’s more, Stiebel Eltron reports that because of its high insulation, this model has the lowest standby loss in the water heating industry.

Now, the company also says that this heater is enough to power a couple of faucets with hot water at the same time. But, I wouldn’t recommend doing so because you’ll run out of hot water pretty fast. Even though it has a fast recovery rate, since it’s not a tankless water heater, it’s going to take some time for the water to get heated again.

When it comes to the warranty, Stiebel Eltron is a bit better than Bosch. For this model, you’ll get a 6-year warranty for the tank and two years for the components.


Now, let’s talk about the installation. Even though it is a tank-type heater, the process is pretty simple, and there’s no hardwiring required. All you have to do is plug it into a 120 V outlet and it’s ready to go.

However, keep in mind that if you install the heater yourself, the warranty becomes void. When it comes to this heater, I recommend paying an electrician or handyman to do it instead.

You should check with the owner’s manual before you start to make sure you’ve got the components you need. I would recommend this heater for smaller households or apartments. It could also be a good fit for an RV, cabin, or office.

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Types of Under Sink Water Heaters

To start off the under sink water heater, let’s talk about which types you can buy. The two main types of water heaters are with and without a tank.

Water Heaters with a Tank

The first thing you should know about these heaters is that they’re easy install. The process only takes a few hours, and you can easily do it yourself.

Also, under sink water heater that have a tank are usually a great choice for larger households. They can supply multiple faucets with hot water at the same Beautiful mother looking at daughter in bath robe while standing in bathroom while washing her hands in the sink with a water heater underneathtime. However, they do take a little bit of time to heat the water at first.

What’s more, they can have a significant standby loss because they’re constantly heating the water. Another thing to note about these under sink water heater is that they’re usually larger compared to sink tankless water heater and you would need a bigger storage area.

I would recommend installing an under sink water heater with a tank if you want to connect it to multiple faucets or appliances at the same. They can last anywhere between 10–15 years, and you can easily replace the parts if they get broken.

Tankless Water Heaters

On the other hand, we have tankless under sink water heater, which is extremely energy-efficient. Since they only heat water on-demand, there’s no risk of a standby loss.

Also, the process is pretty simple, and depending on the size, you can put them under sinks or in your bathroom. What’s more, they have a life expectancy of about 20 years, which is the main reason I wanted to include them in my under sink water heater review.

But, tankless heaters might not be a good choice if you need to supply multiple faucets with hot water at the same time. Keep in mind that if you hook up a sink tankless water heater to a dishwasher, you might not have enough hot water for your faucet.

Types of Tankless Water Heaters

Another thing to consider before buying a tankless heater is its type. If you go for a tankless heater, you can choose between:

  • Non-condensing
  • Condensing
  • Condensing hybrid

Non-condensing under sink water heater are extremely reliable. Since they have an exhaust system, you don’t have to worry about corrosion. However, they are less efficient compared to the other two types. Also, they drain a lot of hot water in shorter draws.

The condensing heaters are a bit more efficient, and they work better with shorter draws of hot water. Also, you can vent them using inexpensive PVC systems. However, they require a lot of maintenance, and you need to clean them at least once a year.

Finally, you can get the condensing hybrid to go under your sink. These are by far the most efficient ones, and they don’t struggle with short water draws. But, keep in mind these are a bit more expensive and difficult to install compared to the other two types.

Things to Consider

In the next part of my under sink water heater, I’m going to talk a bit more about how to find the perfect heater for you.

1. Size

Let’s just say, when it comes to water heaters  — size does matter. The heaters that I’m going to show you in my under sink water heater all come in different sizes so you can find the best one for you.

Leaking steel pipe under sink with water dropsNow, if you go for the heater with a tank, you’ll be able to supply more faucets with hot water. On the other hand, if you choose a tankless one, you’ll be able to power only one or two faucets at the same time.

2. Warranty

While it’s true that sink tankless water heater has a 20-year life expectancy, the warranties are a bit different. Most manufacturers only offer two years for parts and a couple more for repairs.

With that said, depending on the materials used for the heaters, the parts are usually easy to replace. What’s more, some manufacturers even offer a lifetime warranty for their under sink water heater.

3. Installation

If you’re handy with tools and want to save some money, you should consider installing the heater yourself. Even if you’ve never done anything like it before; there’s no need to worry.

There are some good instructional videos and articles online to help you with the process. But, if you decide to call a contractor, make sure to ask for references. Also, ask for a cost estimate up front and check the price, so the installation doesn’t blow your budget.

4. Location

Last but not least, you should consider the climate of the area you’re living in. If you live in a country where temperatures run higher, you can go for a smaller water heater. Since the temperature affects how well your heater performs, you can use a smaller heater to supply hot water to multiple faucets.

However, if you live somewhere with colder weather, you might want to go for a bigger water heater. In my under sink water heater, I’m going to show you size charts for all of the heaters, so you know what to expect.[/wpsm_titlebox][wpsm_titlebox title=”” style=”3″]

To Conclude

Now that you’ve seen my top choices, it’s time to wrap up the under sink water heaters reviews and declare a winner. But, first, before you commit to buying a heater, you need to decide which type you want to get.

If your number one priority is having hot water on-demand, you might want to go for the tankless type. On the other hand, if you have a larger household and want to connect the heater to multiple appliances, you should check out the tank-type ones.

With that said, the water heater that came out on top for me is the EcoSmart ECO 11. The reason why I chose it as my winner is that it’s big enough to give you a good hot supply in all climates.

Also, it’s easy to install and comes with the necessary equipment you need to install it. But, the main reason I chose the ECO 11 is the lifetime warranty, which is an invaluable thing to have. I hope my under sink water heaters reviews have been helpful and that you’ll be able to find the best heater for your needs.[/wpsm_titlebox][/vc_column][/vc_row]

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