The Complete Guide To Best Under Sink Water Heaters

Sep 16, 2021 | Home Repair, Plumbing

We all want to save money on our energy bills, but it’s hard to know which water heater will be the best choice for your home.

Water heaters are expensive and not something you should buy without doing some research first. You don’t want to make a mistake that costs you thousands of dollars in wasted energy over the next few decades.

This article is meant to help you understand how different types of water heaters work and what factors affect their efficiency so that you can choose the right one for your home.

The 6 Best Under Sink Water Heaters

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


Bosch Electric Mini-Tank Water Heater Tronic 3000 T 4-Gallon (ES4) – Eliminate Time for Hot Water – Shelf, Wall or Floor Mounted

  • CONVENIENT HOT WATER HEATER: 4 gallon point-of-use mini-tank fits under your sink to provide hot water right where you need it. Thermal efficiency is 98%. Dimensions : 13.75 W x 13.75 H x 13.5 D Inches

The Bosch Electric Mini-Tank Water Heater Tronic 3000 T 4-Gallon is a time-saving option. It pumps out hot water way more quickly than other electric heaters, so you save time waiting for your sink to come up with any kind of usable hot water. If your primary heating source is far from the sink, this heater will come in clutch for individual or supplementary use. Never have to worry about switching between warm and cold again when using this POU electric heater as an infra-red device works constantly to ensure a continuous output of warm water. This unit is perfect for kitchens where sinks are far away from main sources of natural or propane heated water; it increases the efficiency of conventional gas furnaces that do not heat water to near the temperature that is needed for use. Save time and money by heating up only what you need with this compact under-sink heater.

2. EcoSmart ECO 11 Electric Tankless Water Heater


EcoSmart ECO 11 Electric Tankless Water Heater, 13KW at 240 Volts with Patented Self Modulating Technology

  • Endless On-Demand Hot Water; Consistent hot water when you need it that never runs out; Continuously monitored water temperature and controlled flow rates ensure efficiency and consistent performance within 1 degree of selected temperature

You won’t experience the annoying over-heating that you might find with a traditional model. The unit provides up to 2 gallons of hot water at any time and is equipped with self-modulating technology, which will control energy output based on regional conditions. This unit can provide maximum heat capacity for two sinks or a shower while automatically adjusting in colder climates where one sink may be all it’s able to handle. Additionally, the ECO 11 is designed for under-the-sink installation only so tight corners don’t have an effect on its effectiveness–even your kitchen faucet.

3. ECOTOUCH Tankless Water Heater Electric

Tankless Water Heater Electric 5.5kw 240V, ECOTOUCH Point-of-Use Hot Water Heater Digital Display,Electric Instant Hot Water Heater with Self-modulating,Overheating Protection,White

  • 【INSTANT & SUFFICIENT HOT WATER】Applied with 5.5KW heating system, the electric water heater supplies instant, consistent and endless hot water of 116℉or higher temp shortly, no waiting for preheat nor terrible temp up & down, perfect companion for sinks. Time to get rid of those “lukewarm” toys.

Whether you’ve got an aging dishwasher or if your dish rack is stacked up with charred pots and pans, a brand new ECOTOUCH Tankless Water Heater Electric will be the perfect match. No more waiting for water to reach an acceptable level of warmth, now with this under sink water heater you can live in blissful hot water luxury—every day. And since we understand that not everyone wants their morning tea at 120 degrees Fahrenheit, the ECOTOUCH has a built-in thermostat that ensures only your perfect desired temperature is served. Though it could have turned out very differently (pun intended), look how nice and neat this little guy looks beneath your sink? A beautiful upgrade to lukewarm living.

4. Camplux ME25 Mini Tank Electric Water Heater 2.5


Camplux ME25 Mini Tank Electric Water Heater 2.5-Gallon with Cord Plug,1.5kW at 120 Volts

  • Saving Energy & Money – Built in insulation foam, reduces heat loss. 2.5-gallon point-of-use mini-tank fits under your sink to provide hot water right where you need it.

The Camplux ME25 Mini Tank Electric Water Heater is a good choice for you to save energy without sacrificing convenience. This particular model does not have an output of more than 120 gallons per hour, which can help with the savings. With this appliance in your home, you will be able to enjoy hot water any time that you need it thanks to its 2.5-gallon glass-lined tank and CSA-listed temperature/pressure relief valve. Other great features include installation being generally easy as long as there is cold water access under your kitchen sink, and ease of use–simply plug the unit into a standard 120V electrical outlet near where it will be installed.

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


Eccotemp EM-7.0 Mini Storage Tank Water Heater

  • Great for use on boats or in RVs, cottages, and kitchenettes

Knowing that everyone needs easy access to hot water, Eccotemp has made a heater worth its weight in gold. No need for endless pots of coffee waiting before every meeting or industrial task; the EM-7.0 is here with instant relief. Take this miniature wonder anywhere you go and whip up anything your heart desires on the fly. You’ll never have to worry about running out of water again – we make sure your kettle stays full and ready at all times.

6. HS-4 1 Gallon Electric Tankless Water Heater

RINKMO Electric Tankless Water Heater 18KW 240V Instant Residential Electric on Demand Water Heater for Bathroom Bathtub rv Whole House and Point-of-Use Shower Sink Small

  • 💧【INSTANT ENDLESS HOT WATER】: RINKMO 18KW tankless water heater requires 2 x 40 AMP breakers and 2 x 8 AWG wire, the Water Flow is 0.4GPM/1.5L/min. You aren’t limited to the amount a storage tank heater can hold, tankless water heater technology will instantly supply the hot water your lifestyle demands.

The HS-4 1 Gallon Electric Tankless Water Heater is amazing for anyone looking for a heater that takes the guessing out of setting your desired water temperature. This waterproof, stainless steel product will adapt to any preferences depending on how much you use it, thanks to Pending Closed-Loop Modulation and an Activating Quarter-GPM Flow Rate. With a range of temperatures from 80°F to 140°F, this unit will be sure to handle any need.

Type of Under Sink Water Heater

An under sink water heater can be electric, propane gas, or natural gas.

Electrical Water Heater

This type of water heater uses electrical power to heat potable water and is usually installed under a kitchen sink or counter near an existing faucet. The main advantage to this type of unit is that it does not need any form of the flue, venting, or natural gas line; however, there are many disadvantages, including the high cost in comparison to other types, limited efficiencies/energy factor ratings & potentially dangerous if used improperly (when compared with LP models). Under Sink Electric Tankless Water Heaters typically have very short warranties ranging from 1 year up to 3 years depending on the manufacturer.

Natural Gas Water Heater

There are two types of natural gas water heaters, direct vent, and vent-free. Direct vent units are recommended only for countertop installations because they require a chimney or flue. Vent-free models can be installed either under the sink or on a wall but must not be installed to the side of the cabinet due to combustion gases/carbon monoxide emissions which can enter the room in extreme cases.

Propane Gas Water Heater

The most popular type of tankless water heater is propane because it is inexpensive, offers high energy efficiency & can power multiple appliances at once (including an oven). However, installation requires both plumbing and electrical services and should only be used with appliances that have self-venting designs. Propane water heaters also require annual maintenance to ensure safe operation, but they are the easiest type of tankless water heater to install as long as you have access to a gas line.

Under Sink Water Heater Features to Consider

There are many important features to consider when purchasing an under sink water heater, including type, flow rate, energy rating, dimensions, heating capacity, voltage, warranty, installation & maintenance, and safety features.

Flow Rate

When considering flow rates, it is important to consider all demands for hot water in your home. For example, if you need a lot of hot water in a hurry you may want to choose an under sink water heater with higher GPM and if you live alone then maybe 1.5GPM or even lower would work just fine. Be careful not to overestimate the demand on your unit as there are no benefits from having too large of a unit other than spending more money upfront for something that could potentially not do the job you need it to do.

Energy Rating & Efficiency

Another factor that will affect your energy bills greatly is the energy rating which includes both Btu/h and AFUE. A lower energy rating will not be as efficient as a higher one, but keep in mind that it is always better to have less power consumption than more. Since you want the most bang for your buck choosing an under sink water heater with the highest Energy Factor (EF) rating is ideal. The EF describes how well a unit transfers heat from combustion to the water and includes a number between 0 and 1 which is based on efficiency at different Btu/h ratings so you can rest assured knowing that this is important when shopping around.


When measuring for an under sink heater remember to add at least 4 inches above your existing faucet height. This additional space ensures correct installation & provides evaporative cooling which is vital for the unit’s function.

Heating Capacity

Heating capacity is another important factor to consider when purchasing an under sink heater because the higher the Btu/h rating, the larger your tank will be. Keep in mind that no matter how large your unit is, it cannot provide endless hot water and will shut off once the pre-set temperature has been reached. For this reason, you should choose a water heater with at least 20% more heating power than what your household needs.

Safety Features

Safety features are always a good thing to have and having them on your water heater is even better. Here are some important safety features that you should look for when shopping around: an automatic ignition shut-off, overheating protection, freeze protection & an auto-fill device.

Installation & Maintenance

Although installation is very easy with most tankless water heaters, make sure to do thorough research before purchasing any under sink water heater. Most units connect directly to existing under sink plumbing but there are other models that require removal of the existing water heater which can be costly if purchased at an appliance store (see Home Depot here ). Another thing worth mentioning is the importance of regular unit maintenance – as it is vital to prolonging the life of your equipment and ensuring it is safe to use.


Most under sink water heaters require an indoor air vent that must be installed before you can connect the unit. Vents tend to be a bit more expensive than regular installation but they are well worth the additional cost in the long run because it adds safety & prevents exhaust fumes from escaping into your home. Regularly check your vent for blockages and make sure airflow is free & unobstructed at all times when using your heater.


As with any appliance, a good warranty is always important to look out for. Not only does it protect you should something go wrong but most reputable brands will offer extra features such as extended warranties or even free (non-expiring) in-home service calls if needed. Some manufacturers provide lifetime coverage which goes to show how confident they are about the quality of their unit & its function long term – all under sink water heaters come with at least 1-year parts & labor warranty.


Although price and cost can often be used interchangeably, there are some differences that need to be noted here. Whereas cost takes into account multiple factors such as brand name and popularity, price only looks at your total initial investment without assessing value; so the price is what you pay while cost is what you get. Obviously, with a larger initial investment comes more peace of mind and better long-term reliability.

You’ll also find that there are multiple features to consider when shopping around for an under sink water heater (such as heat settings, type/size tank, maintenance requirements) all of which affect the total cost both short and long term – read our article about factors to consider before buying an under sink water heater if you’d like more information on this topic. The point being made here is that just because one unit costs less than another it doesn’t necessarily mean that it’s the best option for your needs.


A common people make when purchasing a new water heater is buying one that’s too small. Keep in mind that a water heater is only meant to provide endless hot water under set conditions – but this will not be the case if you purchase an undersized unit. You should always have at least 20% extra capacity to make up for the loss of energy efficiency and heat output when your water heater cycles on & off.

For example, a family of 4 living in a house with 1 bathroom would need at least a 50-gallon tank (4 people x 2-3 showers per day = 8-12 daily uses) to ensure they can take as many hot showers as needed at any time without running out of hot water before the end of the day. A 40-gallon tank falls short by 10-20% which can become a serious problem when you need it most (i.e. kids racing to the bath after soccer practice).

Temperature Settings

As with any modern appliance, water heaters come with a wide range of customizable features such as output temperature & timer functions that are designed to improve safety and prolong unit life. For example, some under sink water heaters have built-in 20-40 degree Fahrenheit temperature increments so you can get just the right combination of hot & cold for your needs – read our article about this topic here. On top of that, automatic timers will turn off units after 1 or 2 hours (or whatever time frame you prefer) – automatically turning on again every – which helps eliminate wasted standby energy.

Recommendations & Tips

When installing an under sink heater always leave at least 4″ above your faucet for clearance in case you ever need service or want to replace the unit. For better results make sure that the plumber installs venting/ventilation for ventilation and installation near an existing drain is ideal when considering height restrictions (remember that installation on top of most sinks could interfere with cabinet doors). Generally speaking, electric units are best suited for 1-2 people while propane is recommended for larger households of 3+ people. Remember, no one likes cold showers so consider purchasing a tankless water heater with a high flow rate for maximum comfort.

Pros and Cons of Under Sink Water Heaters

There are several pros and cons of choosing an under sink water heater.


  • Can mount directly under your sink which saves space and reduces clutter.
  • Can be configured to provide endless hot water (tankless on-demand heating) whereas tank-based heaters provide a limited supply of warm water.
  • You never run out of hot water with this type of unit.
  • Most units can operate without venting but will work better when vented properly (more reliable and safer).
  • Most models regulate the temperature automatically so you don’t have to worry about it.


  • Shorter warranty than traditional storage tank models – typically 1 or 2 years instead of 10-12 years for regular tank heaters.
  • Higher initial investment cost compared to regular tank heaters that use a thermocouple.
  • If the power goes out there is no backup heating method so you have to wait for the electricity to come back before you can take a hot shower.
  • Under sink water heaters work great but do require some extra attention during installation (so that they vent properly and there are no leaks). They produce endless hot water at the touch of a button without wasting any extra energy when compared to traditional tank units.

Taking Care Of Your Under Sink Water Heater

There are some important things that you can do to make sure your under sink water heater is working as it should. When we look at other appliances, regular check-ups play a huge role in maintaining their performance and lifespan. It’s only fair if the same goes for our appliance too.

It’s normal practice to give an outline of how maintenance works with any product or machine, so I’ll start there before getting into what this entails specifically when it comes to these types of heaters.

Like I mentioned earlier, there are a few things that you’ll need to check on regularly. Although this might sound like a task and a half, it really isn’t that much extra effort – especially when you consider the potential rewards as well as all of the benefits that under-sink heaters provide in general.

After reading about these appliances, you’ll likely still have a few questions and uncertainties regarding them before going ahead with your purchase and installation. However, if everything checks out and you’re satisfied with what they can do for you then it’s time to take care of them properly so they truly shine.


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