Holds a Master’s degree in Engineering and is keen on her own home’s climate. Sometimes we think that Carolina owns every single product she writes about – that’s how profound and insightful her reviews always are.
For 8 years, Richard had been working as an HVAC specialist and AC unit installer since his student years. Now, he’s our main consultant on every technical aspect that may arise during our tests and research.
Last updated: March 01, 2021
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Thanks to the tremendous advancements in modern technology, our daily life has become a lot easier and better than the life of the people who lived before us. One of the numerous technological inventions that have bettered our lives and have injected a lot of luxury into how we live is an under the sink water heater. With the best under sink water heaters, you can now instantly fulfill your immediate water needs whenever you want, which is especially useful during the cold winters. Compact, practical, energy-saving, and economical, these machines are designed to effectively solve all the issues that usually come with the cold weathers.
Just like the name suggests, these small water heaters go under kitchen counters, under kitchens sinks, or in restroom closets, making them a lot more compatible. However, while you may have decided to buy an under sink water heater for your hot water needs, you may not know exactly where to start from or what to buy, since the market is littered with hundreds of options. Thus, we’ve chosen to come to your aid with an extensive buying guide in which we have compiled six of the best models. To aid our selection, we considered a couple of factors which include the type of the heater, recovery rate, dimensions, ease of maintenance, and warranty.
As usual, we have invested a lot of time into this compilation, just like we’ve always done for our previous guides. For optimum effectiveness and to ensure that we provide our readers with maximum value, we have included an intuitive comparison table that compares our picks and their specifications. Not only that, but we’ve also comprehensively reviewed each of our picks, making sure that you clearly understand the strengths and weaknesses of every heater. Moreover, we have included an enlightening buying guide to help you with your shopping.
You only need to look at the Bosch Electric Mini-Tank Water Heater once to realize that it’s quite different from other water heaters. The Bosch ES4 Water Heater is one of the best under-sink water heaters in the market, and it might be everything required if you don’t want to be replacing your water heater frequently. For optimum durability, it features a glass-lined tank and solid construction means it can endure compression and stress. This water heater is a product you’re likely to use for a very long time without worrying about it getting damaged or becoming less functional.
Apart from being a high-quality water heater, this unit from Bosch is compact in size as well, which is actually one of the primary benefits of under-sink water heaters. This product is so small that it could sit well under the kitchen sink with no movement obstruction, thereby allowing you to save a lot of space. On a similar note, the Bosch ES4 Heater can be either installed on the floor or be fixed on a wall, so this water heater gives you many installation options. The most vital thing is to choose what you’re most comfortable with since the installation option you choose won’t likely affect the performance of the product.
Furthermore, this water heater has a fast recovery rate, which ensures that you don’t have to wait for long before getting on-demand hot water. However, no human invention is made without flaws and there is no difference with this one as well. In our research, we could only find one flaw for this product, and that is its limited warranty. While the six years is quite impressive, the fact that it’s limited is unimpressive, especially when it’s compared to other top models from similarly big brands.
With its extremely compact construction and its ability to help you save on energy bills by up to 60 percent, the EcoSmart 8 kW Electric Tankless Water Heater is the right choice if your kitchen isn’t really large. While it’s referred to as a heater for the whole home, its 1.5-gallon per minute flow rating means it’s best used for homes with only one bathroom. It’s recommended by EcoSmart to use the Eco 8 in homes where the temperature goes as high as 60 degrees or low as 70 degrees.
To allow for easy installation, the electric tankless water heater comes with a compression fitting and an adapter for compatibility with other systems. And due to the fact that it’s smaller and more compact than other models, it consumes less power and it’s very easy to install. And should you have any issue or questions regarding the system, EcoSmart has a customer service that is totally dedicated to helping customers solve their issues as soon as possible.
While it is smaller and consumes less power than other models, it still features a digital display on the front which allows you to have more control over the operation of the device. The built-in silver knob allows you to choose between a Fahrenheit and Celsius readout and also adjust the temperature. Moreover, it’s backed by a lifetime warranty that’s only effective when you use it in a residential home. The only apparent limitation of this device is its inability to generate piping hot water at high flow rates.
While the Camplux ME40 Mini Tank Electric Water Heater isn’t a model designed for regular usage, it is an excellent small capacity unit that is perfect for places where hot water isn’t regularly needed. With its four-gallon tank capacity, it offers you access to a lot of hot water in some areas where it would be unnecessary to have a larger tank. Like our editor’s choice, this one also has a glass-lined water tank that aids durability, which makes it damage resistant and helps it to maintain a lengthy service life. And it also has multiple installation options – floor, wall, or shelf – which offers you a lot of flexibility.
While this electric water heater also has small dimensions and a lot of flexibility, its performance is the highlight of all its features. Featuring a thermostat control, you can easily make adjustments on the water temperature and set it to your preference. Since the unit has a heating scope of about 50 degrees Fahrenheit to 140 degrees Fahrenheit, you can easily adjust it to the ideal level. And even though it has a high range of temperature, you can be sure that there won’t be an issue of overheating as it has an incorporated high limit overheating protection.
The heater has intuitive and simple controls too, which let you regulate the thermostat easily. There is a red indicator under the dial that lights up whenever the water has reached the required temperature, which eliminates guessing games and allows you to know when the water is ready. The only thing most people don’t like about this product is the fact that installing it by yourself voids its one-year warranty.
If an effective small tank water heater is what you’re looking for, the Stiebel Eltron SHC 2.5 is a quite worthy investment. It comes with a four-gallon water capacity, which makes it one of the most appealing choices on the market. And you only need to plug the heater into an outlet of 120 volts in order to enjoy it. With a power rating of 1,300 watts, this mini heater from Stiebel Eltron is one of the most powerful heaters on this list. It is the kind of heater that every homeowner would want for their home.
Some of the other functional specifications you might want to know about this stunning heater include the included bracket for mounting, glass-lined tank, fast recovery, and T and P valves. As regards the temperature features, this device can be adjusted to up to 140 degrees Fahrenheit, making it a very flexible option. Besides, it has a very quiet operation, which makes it a very great choice for people who adore quietness and serenity more than anything in the world.
Although the majority of the features built into it make it a valuable addition in every home, there are some reports that the device leaks water at the base. While the problem doesn’t apply to each one of this model, the risk of having leaks and probably damaging home features remains. It’s very important that this product is maintained properly to avoid occurrences like that from occurring. Apart from the potential leaks, this machine also tends to have low pressure when you use it with multiple washing appliances.
What we liked:
Very powerful operation
Decent recovery rate
Multiple installation options
What could be better:
There is a possibility of leakage
Low pressure when it’s used with multiple washing appliances
Coming from a rather reputable company in Eccotemp, the Eccotemp EM-2.5 is another effective machine in which your trust can be invested. Despite coming with a relatively small 2.5-gallon water tank, it has an incredible heating performance. Among the numerous features built into this model is the temperature control, which allows you to effectively increase the heating temperature from 50 degrees to 140 degrees. Apart from being perfect for under-the-sink usage, the machine is also ideal for bathroom usage.
Furthermore, the heater has a compact and lightweight construction, and it can even be hung on the wall if you’re looking to save space. In addition to that, the Eccotemp machine has a fast recovery rate, which enables you to have on-demand hot water whenever you desire. Not only that, but the machine also comes with a pressure relief valve which enhances safety and protects the heater adequately. Indeed, this model is worth looking at if you are looking for a water heater that is effective and not just overhyped.
Furthermore, this water heater comes with a five-year warranty, which is actually a good deal. While it’s been reported severally that it is a bit slower in its operation when compared to some other models from other brands, it still works at the end of the day. It is a decent option if you’re looking for a decent machine for under-sink purposes and you’re willing to have a great hot water experience.
What we liked:
Lightweight and compact
Has a temperature knob
Offers protection with the included pressure relief valve
If you don’t like waiting for your on-demand hot water and want to actually reduce the time you need to wait for considerably, you will really love the Thermoflow UT10 Water Heater. Being equipped with a small water tank that is capable of heating up to 2.6 gallons, this machine may be insufficient for the whole water heating system of a home. However, it will be totally perfect if you only need to use for a certain sink, and not more than one sink. It’s outfitted with a heating element and stainless-steel tank engineered for durability, easy replacement, and efficiency.
Going forward, the Thermoflow has a thermostat that allows you to choose the right and comfortable temperature for you. With that, regardless of how hot you want your water to be, you can easily adjust the machine and set it to stop at your preferred temperature level. Besides, the machine also has an energy-saving mode and a frost protection mode, which make this little unit from Thermoflow a suitable option for all seasons. Like most top-of-the-line models, this one also heats water quickly and has a fast recovery rate, with the incorporation of a special EPS Foaming Technology.
Apart from being easy to install, this unit is also safe to use, thanks to the inclusion of an active protection circuit known as Thermostop. The circuit is designed to disallow overheating, stopping at the most ideal temperature for you. However, most users complain that this unit is too big to fit conveniently under their sinks alongside other things that are customarily put under the sink.
What we liked:
Easy to adjust
Fast recovery speed
Heats water quickly
Highly durable and efficient
What could be better:
Construction is too big for an under sink unit
Things to Consider
Under sink water heaters just started becoming popular recently, so buying the right one might not be as straightforward as it seems. With that in mind, we have compiled this handy buying guide below to help aid your decision.
An under sink water heater: advantages and constraints of having one
Before you decide to get an under sink water heater, which would be considerably more compact than a water heater you’d use, for example, in your bathroom to take a shower, it makes sense to consider possible pros and cons of having one.
Time-saving – Undoubtedly, an under-sink water heater helps you to save time. Rather than you wasting your time or having to wait for the water to get heated up before getting conveyed to you from an orthodox water heater located at a distance, you can instantly get hot water and save much of your time.
Saving Water – Using an under-sink water heater can also save you thousands or at least hundreds of gallons of water. Rather, utilizing an under-sink water heater will allow you to instantly get hot water, thereby saving lots of water which would be wasted otherwise due to the delay between switching the faucet on and actually getting the heated water.
Suitable for People Living in Large Houses – For people living in large houses that have a central water heating system, heated water can take some time before it reaches distant outlets, thereby causing lots of inconveniences. In addition, if there is a remote sink inside your home that isn’t served by a tank-type or tankless water heater, setting up an under-sink water heater can be a really convenient method of helping to get rid of any unnecessary waiting time and also avoid water wastage.
Cost-Effective – When you take their longevity and functionalities into consideration, under-sink water heaters are very affordable and reasonably priced. In addition to that, they are simple to maintain and help cut on energy consumption.
Increase in Electricity Bills – The machines may demand a lot of electrical energy in order to function well and effectively heat the water at the right temperature. The electrical bills swell since you are not heating the water with a gas tankless water heater.
They require refilling – The water heaters require replenishing most times due to the fact that you’d need to carry out the task regularly once you’ve connected the machine to the water supply. Since it can always be difficult to fill up all of it, most of them have to be connected to the water supply pipes. Then, look out for humidity-causing leakages in the kitchen.
How does it work?
Engineered to be set up under the kitchen sink, most under-sink water heaters generate up to sixty cups per hour. Some models can be adjusted from 140 degrees Fahrenheit to 190 degrees Fahrenheit, so you can choose the right temperature for you. Others are made to heat water to a certain temperature set by the maker and the unit. While preset temperatures usually vary, several units are engineered to heat water a bit below boiling point or up to 200 degrees Fahrenheit. If you intend to make coffee with your instant hot water system, select a model that reaches something between 190 degrees and 205 degrees – the perfect range to brew a delightful cup of coffee.
There are essentially three components to the heating system – an inline filter, a holding/heating tank and the faucet or dispenser. The inline filter helps eliminate impurities in order to make your hot water clear, crisp and unclouded, and it’s usually connected to the supply line of the cold water. Most inline filters have two chambers – one for holding the cold water supply while the other one for heating the water and holding it at a consistent temperature so that it’s available instantly.
Hot water comes out as soon as the tap is opened. As the heated water leaves the holding/heating tank, clean cold water is then drawn from the holding chamber to where it is heated in the hot water chamber. Simultaneously, cold water is drawn and funneled through the filtration unit and into the cold holding chamber. It is a very effective and simple procedure that actually happens in less time than its description takes.
Features to consider while choosing an under sink water heater
There are a couple of boxes required to check prior to purchasing an under sink water heater to ensure that you make the best choice. Below is a list of the factors you have to keep in mind during your shopping.
Tank or tankless
Choosing between a tank-style or tankless model when selecting the most ideal water heater for your needs greatly depends on your preference and many factors. While the initial cost of the tankless unit is higher, it is smaller, providing on-demand hot water as much as needed, where one big unit like the Bosch Electric Tronic 3000T ES4 is capable of supplying up to three to four fixtures at the same time. Tankless models are usually environment-friendly and condensing while tank-style models can supply more than one fixture simultaneously with no temperature inconsistency.
All under sink water heaters and even some over the sink models store water, which means you have to keep their capacity and their demand in mind. The hot water you utilize is immediately replaced by cold water, which can then mix with the heated water. The cold water usually heats up within a couple of minutes.
If you live in an area where the demand for instant hot water is high, you will need to strike a balance between sufficient water being generated and a great reheating time. As a rule of thumb, you will get about half of the tank’s capacity in hot water prior to it becoming warm. First of all, think about what you intend to be utilizing it for, and also think about the amount of water you will likely be needing at a time.
High flow rate
Another important consideration you need to always keep in mind is the flow rate. It’s important for you to choose a model with a high flow rate in order for your hot water access to remain uninterrupted. Some models might have up to five GPM flow rate, it all depends on the model. Undoubtedly, you will like it if you can always use hot water in the shower and the faucets at the same time.
Regardless of the type of water heater you’re buying, the energy rating is another important consideration you must keep in mind. This is very essential as the energy rating usually determines the machine’s capacity to function superbly without consuming high energy. Precisely, an under-sink water heater that has a high energy rating will clearly indicate it that it’s capable of heating a large amount of water while using minimal energy.
Size is indeed one of the most vital factors since it determines the nearness reference. Therefore, it would be required to be aware of that fact that tank-style heaters are considerably larger and they can never compare to the fitting of tankless models even though they might fit under your kitchen sink. So, ensure that you measure your installation area upon purchase and find the heater’s size before you go ahead to buy it.
A good warranty, sometimes, is everything you need when buying an under sink water heater. The warranty terms might vary often depending on the brand and the manufacturer. Choose a model that offers a longer warranty period as it’s usually a solid indication of durability. You might even come across models that come with a lifetime warranty like the EcoSmart 8 KW Electric Tankless Water Heater.
Regardless of the technology type, you must carry out three operations on a regular basis:
Operate the draining lever of the pressure relief valve so as to prevent jamming in the event of deposits. We recommend doing it once every month.
Drain the tank of your water heater or hire a professional to drain it for you every two years at least in regions with hard water. As a result of this action, deposits of scale on the heating element is thereby eliminated.
Check the condition of the electric wires, the electrical connections, the thermostats, and every other regulation device.
A tankless water heater is more economical than a tank model, which is as a result of its higher energy efficiency. In fact, a tankless model can be 24 percent to 34 percent more energy efficient than conventional water heaters, thereby helping to reduce energy costs by up to 25 percent.
An under sink water heater can actually be utilized for three various purposes: as an independent heating system for a single kitchen sink, as an addition to an existing water heater installed far away from the kitchen sink, and as a cushion installed in-line with a tankless water heater that experiences irregular cold water.
Of course, an under sink water heater can be installed in your recreational vehicle. As a matter of fact, there are no water heaters that are designed specifically for RV, so experts usually recommend tankless with small construction for RV usage. Under sink water heaters are totally perfect for RV use.
Under sink water heaters are usually electric types, and rarely require extra complex machinery, which makes the installation process a rather straightforward affair. You can install it by yourself, of course, but you have to ensure that the warranty of your specific model isn’t voided by self-installation like the Camplux ME40.
Our editor’s choice is the Bosch Electric Tronic 3000T ES4, and the reasons aren’t difficult to figure out. Being backed by a six-year warranty, it’s even needless to say much about the amount of confidence Bosch has in this particular model. Optimally durable, exceptionally functional, , you can’t find a better option than this model, compatct as any portable water heater.
Our second choice is the EcoSmart 8 KW Electric Tankless Water Heater, and we mustn’t forget to mention how stern of competition it gave our first choice while making our conclusions. In addition to its extraordinary performance, it also has a lifetime warranty, which might actually make money people wonder why it’s not our first choice.
The tank-style Camplux ME40 with a four-gallon water capacity is our third choice, and for good reasons. With its intuitive and straightforward controls, this unit is effortless to use, and that’s only a complement to its incredible durability and performance.