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On-Demand Hot Water – Our Guide to Best Under Sink Water Heaters

You know those cold winter days when the last thing you want is having to use freezing water? Gone is the torture of shaking hands under the ice-cold stream of tap water. That is, of course, if you have an adequate heating device in your home. For an instant source of hot water, you may want to consider an under sink water heater.

Best Under Sink Water Heaters

Don’t just believe what we say, keep reading. Find below our carefully researched list of high-performing water heaters. They will fit perfectly under your kitchen counter, sink or in your restroom closet. And to ensure you take an informed decision, we compiled a list of features to look for. Use our guide to understand better what makes a great under-sink water heater.

The utility of An Under sink Water Heater

If your current water heater gets overwhelmed by your requests, you need to upgrade. But that should not necessarily mean replacing it. You can increase the amount of hot water available with an under-sink water heater. It is an affordable alternative to satisfy your needs for hot water.

An under-sink water heater is an electric unit supplying hot water straight to your faucet. As their name suggests, they are usually mounted under a sink. They can be also called point-of-use (POU) water heaters. In general, they function by either heating the water as it’s passing through. Tank-style models preheat a certain amount of water and store it until it’s needed.

Reduce the waiting time with an under-counter heater. These appliances are, by design, meant to supply enough hot water in a matter of seconds. And they can fit in even on your boat, RV, office or garage. You name the place, these heaters will be a perfect match.

Under sink water heaters are, however, not a replacement for your large heating unit. For the best results, you should combine them. Connect the under sink unit to your shower or tap or use it in line with your main heater. Using these small appliances brings advantages like saving water, energy and space.

What to Look For in an Under sink Water Heater?

There are a few important features that can make a difference in an under sink heater. To know what would be best for your needs, space and budget, check out the list below.

  • Type 

Deciding between a tankless model or one that includes a tank varies according to your needs. Tankless under sink water heaters have a higher price, but they don’t keep you waiting. They will take very little space and cover your needs for hot water almost instantly.  On the other side, a tank-style version is more suitable if you want to have hot water in several corners of your home. This way, you enjoy your hot shower in the back room without any annoying variations.

  • Flow rate

If you need a constant hot water flow, your under sink water heater should have a high GPM (or GPH). The number of gallons per minute (GPM) or gallons per hour (GPH) reflects how much hot water the unit can supply.

  • Energy rating

You will enjoy constant hot water, but a large electricity bill may be a bummer. The energy rating indicates the heater’s capacity of having a low energy consumption. The higher the energy rating, the lower the amount of energy used to heating a large amount of water.

  • Dimensions

Space is very precious, so you want to make sure you make the most of it. As you can imagine, an under sink water heater with a tank will take more space. The tankless versions are far more practical and can pass unnoticed even in tight places. Take some clear measurements of your available space before making a purchase.

  • Heating capacity

For the best performance from your water heater, balance the demand with its capacity. Think of how much hot water you will be likely to need at a given time. Consider the time that the unit might need to heat up more water, once the stock is over. Simply put, the hot water you use is usually replaced fast by cold water in the heater. It usually takes just a few minutes to heat the cold water. But if you expect a high demand for hot water (e.g. having a big family), check for a heater that can supply it in a timely manner.

  • Voltage

When choosing a heater, make sure that the electrical outlets in your home (or boat, RV etc), can handle the demand. Most units work fine plugged into 120V sockets. For heaters that need 220V for example, you will have to adapt your outlets. Check the model’s electrical requirements to know more.

  • Safety Features

Additional features are always a great thing to have. For under sink water heaters, these include a thermostat, modulation, or a pressure relief valve. A thermostat makes it easier to control the water’s temperature. Modulation translates as the heat output adjustment in response to the flow rate of water that runs through the unit. A pressure relief valve prevents damage caused by excessive water pressure.

  • Installation And Maintenance

You may be the handyman type or prefer to call a professional to help you out with this. Take a look at the installation requirements to get an idea on the process. Some units will only need plugging into an outlet to function. Others may imply electrical or plumbing work to be operational. This is important to check, in order to respect the warranty conditions as well. In terms of maintenance, you want to make sure you can properly use and take care of your heater, to prolong its life.

  • Warranty

Better safe than sorry means you consider the risks that may arise in time. Having a long term warranty for your under sink water heater can put your mind at ease. Especially if you invest a consistent amount of money on it. The warranty terms vary from manufacturer to manufacturer. An extended warranty period is a a solid indication of durability. Some models even come with a lifelong warranty.

Our 6 Most Recommended Under sink Water Heaters

ProductStrengthType Flow Rate Heating CapacityDimensionsWarranty
1. Bosch Electric Mini-Tank Water Heater Tronic 3000 T 4-Gallon (ES4)long-lasting design; best for low hot water demands4 gallons tank6.8 GPH1,440W13.75  x 13.75  x 13.5  Inches6-year warranty on unit, 2-year warranty on parts
2. ECOTOUCH Tankless Water Heater Electricself-modulating technology for optimal energy efficiencytankless120 GPH 
(2 GPM)
13000 W3.75 x 8 x 11.5 incheslifetime warranty
3. ECOTOUCH Tankless Water Heater Electricmultiple safety features; touch control panel for temperature settingstankless90 GPH (1.5 GPM)5500 W11 x 7.5 x 2.35 inchesnot specified
4. Camplux ME25 Mini Tank Electric Water Heater 2.5<suitable for RVs & homes; versatile installation options2 gallons tank6.8 GPH1500 W11.75 x 17.25 x 10.381-year warranty
5. EM-7.0 Eccotemp 7 Gallon Electric Storage Tank Water Heaterideal for various settings (boat, food trucks, RVs); easy to use7 gallons tank135 GPH1440 Watts17.2 x 17.2 x 14.2 inches2-year warranty on parts, 5 year warranty on leaks
6. HS-4 1 Gallon Electric Tankless Water Heaterbuilt-in timer; power consumption adjustment based on real time datatankless120 GPH
(2 GPM)
3200 Watts6.5  x 11 x 3 inches5-year warranty 

1. Bosch Electric Mini-Tank Water Heater Tronic 3000 T 4-Gallon (ES4)

HS 4 1 Gallon Electric Tankless Water Heater

The Bosch Electric Mini-Tank Water Heater Tronic 3000 T 4-Gallon (ES4) is a time-saver. If your primary heating source is far from your sink, getting hot water may mean waiting for a while. Time is precious and the Tronic 3000 T knows it. This POU electric heater is a perfect appliance for various uses. Use it as an individual hot water source for a sink or as a complement for your primary heater. It also works as a buffer in-line with other heaters that do not provide a constant flow of warm water. Forget the hot and cold sensations. Rely on this under sink water heater to supply you with hot water, whenever and wherever you need.


  • compact, lightweight design
  • CFC-free foam insulation – energy efficient
  • made of resistant materials
  • versatile installation options
  • glass lined tank.


  • limited warranty  (6 years)
  • reduced capacity for hot water flow
  • some users accused leaking problems after a few months of usage.

2. EcoSmart ECO 11 Electric Tankless Water Heater

HS 4 1 Gallon Electric Tankless Water Heater

The EcoSmart ECO 11 Electric Tankless Water Heater stands out from the crowd. Using a patented self-modulating technology, the unit controls the energy output. So you can trust them to provide optimal water heating. This under sink water heater can supply properly up to two sinks and a shower at the same time. Its performance varies based on the average temperature of the water in your region. In colder climates, the ECO 11 will handle providing enough hot water only to two sinks at a time. Perfect to use in a small apartment or as a small POU, this under sink heater can ensure up to 2 gallons of hot water per minute. With 99.8% energy efficiency and a lifelong warranty, this unit is a great addition to any home.


  • elevated energy-efficiency rate
  • digital temperature control
  • self-modulating technology
  • lifelong warranty
  • reduced size & compact design.


  • requires more time to supply flowing hot water in colder climates.

3. ECOTOUCH Tankless Water Heater Electric

HS 4 1 Gallon Electric Tankless Water Heater

The ECOTOUCH Tankless Water Heater Electric will turn “lukewarm” water into a memory. Using a 5.5KW heating system, this under sink water heater can provide instant hot water to your sink. No preheating, no more temperature variations. The unit features a smart self-adjustment, based on the flow rate and real-time temperature settings. It will be the perfect match for your sink, ensuring you get a steady flow of water at the ideal temperature.


  • digital display & touch control panel
  • easy to use
  • ETL & UL listed
  • compact design
  • 360 degree installation options
  • over temperature protection
  • dry heating protection
  • leakage protection
  • separate water and electricity line.


  • no remote control for this model
  • for warranty safety, may need professional installation
  • not suitable for shower use.

4. Camplux ME25 Mini Tank Electric Water Heater 2.5

HS 4 1 Gallon Electric Tankless Water Heater

The Camplux ME25 Mini Tank Electric Water Heater is an easy to install, versatile POU. Suitable to mount on a shelf, wall or floor, this unit has a glass-lined tank, meant to last. Enjoy 2.5 gallons of hot water when you need them. Featuring a CSA listed temperature/pressure relief valve, this model is super safe to use.

You can install it without too much hassle. Simply tap into the cold water line under your sink and plug the unit to a 120V source. And you will have an efficient, energy-saving water heater ready to use.


  • easy to install
  • overheat protection
  • glass lined tank
  • various installation options
  • fast recovery rate.


  • one year warranty.

5. EM-7.0 Eccotemp 7 Gallon Electric Storage Tank Water Heater

HS 4 1 Gallon Electric Tankless Water Heater

The EM-7.0 Eccotemp 7 Gallon Electric Storage Tank Water Heater is great for any home, commercial or industrial space. This under sink water heater can supply instant hot water to any faucet in no time. Compact and lightweight, it can easily find its place anywhere you need it to. Take it with you on your boat, RV, food truck or use it to complement your main heater at home.


  • easy to install
  • 98% energy efficient recovery
  • affordable price
  • accessible temperature controls.


  • no thermostat
  • no isolation valve
  • limited warranty.

6. HS-4 1 Gallon Electric Tankless Water Heater

HS 4 1 Gallon Electric Tankless Water Heater

The HS-4 1 Gallon Electric Tankless Water Heater is the waterproof, stainless steel heater you were looking for. Setting the desired temperature is a no brainer, thanks to the interactive touchpad. With a range of temperatures from 80°F to 140°F, you know this unit will save you from being hot and cold. This under sink water heater will get to know your preferences very well. It relies on a pending closed-loop modulation and an activating quarter-GPM flow rate. That means the heater adapts the power consumption based on how much you use the heater. Using real-time data, this unit has a high energy-saving performance.


  • no venting needed
  • digital temperature display
  • thermostat included
  • built-in timer
  • energy-efficient consumption.


  • only suitable for a kitchen sink
  • limited warranty.

Upsides & Drawbacks of Under sink Water Heaters

Any purchase decision should have a strong argument base. So, here are the main advantages and downsides of using an under sink water heater in your home or boat, RV etc.


  • saving time – reduced waiting time for getting the hot water you need
  • saving water – less water wasted in the heating process, as the units release directly heated water.
  • improving comfort in large houses – can complement the primary heating source and provide hot water to the remote areas of the house
  • energy-efficient – low energy consumption in relation with the performance level


  • increased electricity bills – although latest models have a high energy consumption – performance ratio, you will feel their “presence” on your bills as they require considerable resources
  • maintenance costs – you have to periodically be on the lookout for leakages, limescale deposits as these can put in danger the integrity of the heater and your safety while using it
  • considerable investment – some models can be high-performing, but they require you to allocate a larger budget to purchase one

Taking Care Of Your Under sink Water Heater

As with any appliance, ensuring optimal usage can prolong the life of your device. To keep your under sink water heater in good shape, you should consider some regular check-ups. It’s important to keep your water heater in good shape, to avoid additional repairing costs.

Among the things you can do to keep your water heater running smoothly, consider:

  • Verify the pressure relief valves, to avoid overuse.
  • Flush out to prevent limescale deposits in your POU water heater. We advise you do this at least every 12 months.
  • Check for leaks on a regular basis.
  • Make sure the regulators and thermostats are functioning properly.
  • Tighten well the hook-ups.

You can either do this maintenance by yourself or ask for the assistance of a professional. This will help minimize the risks of damage or hurting associated with the use of an under sink water heater.

Final Thoughts

An under sink water heater can be a great addition to your home or holiday vehicles. Compact, powerful and energy-efficient, they provide on-demand hot water, saving you time, water and energy. Scan our guide and list of recommended point-of-use heaters. Find one suitable for your space, needs and budget. And let us know more about your experience of using an under sink water heater.