Best under sink water heater

Best Under Sink Water Heater (Save 70% Utility Bills!)

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Let me Reveal the chart of the best under sink water heater but before that,

What does the Under Sink Water Heater can do except dispensing hot water? 

Even why do you need one when you already have a central water heater installed?

The answer will make you shocked…!!! 

Reason 1: (Suppose your pipeline’s diameter is 1 inch.) If the central water heater remains 5 feet away from the kitchen sink, it wastes 1+ liter water before hot water reaches there each time you open the sink faucet. 

So, if your kitchen sink remains 60 feet away, you waste 36-40 Liter water a day. Almost 14,600 Liter+ waste of water a year!!! Sounds alarming?

Reason 2: Central heating systems are Gigantic, and your Kitchen sink demands only 10% of their capacity. As a result, 90% of remaining hot water waits unused for hours, resulting in massive energy wastage and excessive utility bills! 

Reason 3: If the entire hot water production depends on a central water heater, you won’t get sufficient hot water while using showerheads and kitchen sinks simultaneously. Also, you would have to wait for a long, which is absolutely a waste of time.

Reason 4: If somehow your central water heater fails, all your kitchen tasks will get stuck along with the shower and the toilet chores! Sounds horrible?

Let me share a statistic. We use almost 18-27 gallons of water a day in the kitchen, practically the same amount we use for a shower. 

So, installing an under sink water heater is a fundamental necessity. Additionally, the under sink water heater saves your 

  1. Utility bill, 
  2. Time 

Importantly, it prevents water wastage.

12 Best Under Sink Water Heater Detailed Reviews

1. (Most Popular) Under Sink Hot Water Heater – Bosch Tronic 3000T

Bosch Electric Mini-Tank Water Heater Tronic 3000
  • Tank Size – 4 Gallons (Also Available in 2.5 and 7 Gallons)
  • Recovery Rate – 6.8 Gallons Per Hour at 90°F
  • Power – 1440 Watts
  • Temperature Range – 65°F – 145°F
  • Warranty – 6 Years Tank, 2 Years Parts
  • Water Inlet/Outlet Pipe –  1/2″ Male

Wanna hear a shocking fact? 

80% of American homeowners own a Bosch Tronic 3000T who’s currently using a “tank-type under sink water heater.” Think how popular it is!!!

Lately, I’ll explain the reason behind it.

I would recommend the 4-Gallon model (ES4) instead of ES2.5 or ES8. Cause, firstly, it doesn’t need any hard wiring or additional circuit breaker as any random electric outlet can handle it. 

Secondly, 4-Gallon is pretty much sufficient to fulfill the hot water demand of a kitchen/bathroom sink for a medium-sized family.

The Bosch Tronic 3000T offers a recovery rate of 6.8 GPM at 90°F. While testing in real life, we’ve got almost 2+ Tank (8 Gallons+) of useable hot water each hour.

One more thing! Bosch claims the unit is 98% energy efficient, so we’ve tested the energy consumption. If it continuously runs for a whole hour, it drains 1.37 units of electricity. So the hourly cost remains around 18.23 cents.

Additionally, one full tank of water takes 18-20 minutes to be heated thoroughly.

You’re able to preset the hot water temperature among 65°F-145°F, and we found the outlet temperature remains almost accurate on a constant point. Although, according to a few user interviews, the thermostat starts misfunctioning after long-term use. 

However, we haven’t experienced any critical water boiling noise, and the unit was running smoothly on a 120V random socket. The unit was consuming around 11.7 amp, and the socket & plug didn’t become hot at all.

An Exceptional Feature – Better for Harsh Water Chemistry

Bosch Tronic 3000T is the only tank-type under sink water heater, where you can replace the “Anode Rod” that costs hardly $15-$19. However, if your line water contains extensive minerals, changing the Anode Rod on a yearly/half-yearly basis will severely increase the tank’s lifespan.  

Be Aware of DIY Installation

The 6 years of warranty will only be valid if you install it by an authorized dealer and replace the anode rod at least once a year.

Fact is, We’ve found that the installation cost is higher in few states than buying a new unit. So, self-installation would be a better option if you feel confident about it.

Why is Bosch Tronic 3000T too familiar to the American People? 

BOSCH is the oldest manufacturer of Under-Sink water heaters, and other familiar brands like Rheem, Ariston, Stiebel Eltron, Ecosmart, etc., have started manufacturing it lately.

So, the Tronic 3000T was the first used model for most of the early users. However, lately, they can hardly come out of their old brand preference and chose a new one. Accordingly, satisfied users refer this model to their well-wishers. 

But, of course, there are several other models with excellent reliability and a longer lifespan! You shouldn’t skip verifying them before choosing the final one.

2. (Most Energy Efficient) Tankless Under Sink Water Heater – Rheem RTX-13

  • Flow Rate – 1.5 GPM – 3.17GPM
  • Temperature Range – 80˚F – 140˚F
  • Power – 13KW
  • Temperature Range – 65°F – 145°F
  • Wiring – 60 amp Breaker + 6 AWG Cable
  • Warranty – 5 Years Heat Exchanger, 1 Year Parts

Are you Feeling tired of extensive electric bills? Or hate running out of hot water? 

Then Rheem RTX 13 is a treasure for you, which is extremely energy efficient (99.8%) and eligible to supply unlimited hot water even to a commercial sink.

But, here are two conditions!

Firstly, if you are from colder regions such as northern America, Rheem RTX13 might not satisfy you. Tap-water needs to remain at least above 45°F for optimum performance.

Secondly, the unit requires 240V hard-wiring along with a 60amp breaker and 6AWG cable. Cause the unit draws up to 54~57 amps current while running on full power.

If these are okay, definitely the Rheem RTX 13 is a brilliant choice for your under-sink installation.

Impressive Facts of Rheem RTX 13 (According to Test Result)

Energy Efficiency: We’ve interviewed 7 RTX 13 users and asked them about electric bills. They’ve ensured that their electric bill has dropped around 30%-40% based on daily uses. 

Temperature Accuracy: Rheem allows the user to increment/decrement the temperature by 1°F between the wide range of 80°F to 140°F. 

The LED shows only the preset temperature, so you won’t be able to check the outlet temperature unless using a thermometer.

So, we’ve experimented, and while the inlet temperature was 55°F, we got around 110°F outlet temperature on a 2.5 GPM sink faucet though the preset temperature was 140°F. But I think that’s decent!  

You can raise the flow to 3.17 GPM, but the temperature will fall to 90°F~95°F, which is okay for having a shower or washing hands but not sufficient for dishwashing. 

So bear that in mind; you need to set the flow between 1.5GPM ~ 2 GPM for a tremendous performance.

What’s about Longevity?

The chance of getting defective is very lowest for Rheem RTX 13 if you aren’t too unlucky. 

Rheem contains a Corrisson Resistant copper heat exchanger and offers a five-year warranty. I’ve interviewed multiple users, and none have faced any issue with water heating over a long period. 

But, some users have faced issues with electrical wirings or short circuits due to their messy faulty installation and wrong circuit breakers.

3. (High Capacity) Tank Type Under Sink Water Heater- Ariston Andris

Ariston Andris 2.5 Gallon
  • Tank Size – 8 Gallons (Also Available in 2.5 and 4 Gallons)
  • Recovery Rate – 6.8 Gallons Per Hour at 90°F
  • Power – 2000 Watts
  • Temperature Range – 65°F – 161°F
  • Warranty –  6 Years Tank, 2 Years Parts

If you care about LONG-TERM useability and prefer to install a tank-type under sink water heater, then Ariston Andris is a decent choice!

Though I’m reviewing this unit in 3rd position (2nd tank-type), I swear!!!, it’s my personal preference. Wanna know why?

  1. Among all other tank-type under sink heaters, Ariston Andris requires the least maintenance
  2. Users face no performance drops after years of use. My own unit is currently 4 years old and still working like a new one.
  3. Their customer support is satisfying, and there’s no issue with the DIY installation. (3X better than “BOSCH.”) If you are eligible, you may install it yourself, and the warranty won’t get void at all.
  4. The internal tank layer contains TitanShield coating that keeps it corrosion-free even in relatively rough water. 
  5.  Ariston Andris offers a broader temperature range which is 65°F-161°F, almost 16°F hotter than most other brands.
  6. It produces around 16 Gallons+ of hot water each hour, though once you open the hot water faucet, the cold water starts entering inside, and the temperature starts decreasing. 
  7. Cleaning and rinsing Ariston Andris is relatively easy.

For the higher hot water demand, I would highly recommend the 8 Gallon variant, which is 2000 Watt and consumes around 16~18 amp current during operation (as we tested). 8-Gallon unit doesn’t come with a power plug, so you will require hard wiring in line with a 20 amp circuit breaker for smooth operation.  

Attention Please!! It’s Important.

All tank type under sink water heater contains an anode rod, and the Ariston Andris isn’t different. But the replacing procedure is slightly tricky here. It’s not a hassle-free procedure like Bosch Tronic.

Though, Ariston doesn’t require to replace that Anode Rod too frequently like the Bosch Tronic. 

Utilize The Warranty

I’ve interviewed 17 Ariston Andris users, and their experiences are…

  • If the unit lasts more than six months, that’s going to last for a decade! But,

If you are unlucky, then you might face trouble within a couple of months, for example, tank leakage, thermostat turbulence, and so on. So, without delay, approach customer support and ask for a replacement, and all will be okay!

4. Tiniest Tankless Under Sink Water Heater – ECOTOUCH Smart 5.5KW

  • Flow Rate – 0.7~1.5 GPM
  • Temperature Range – 67˚F – 116˚F
  • Power – 5.5KW
  • Wiring – 30 amp Breaker + 10 AWG cable.
  • Warranty – 1 Year Parts and Service

Ecotouch Smart 5.5 has been manufactured precisely for under-sink installation as it’s slim, underpowered, and definitely eligible for delivering hot water restlessly with a 1.5 GPM (MAX) flow rate.

(A matter of regret, some people criticize ECOTOUCH for their own stupidity! Clearly, the unit can deliver hot water at a 1.5 GPM maximum flow rate, and there’s no way of expecting a satisfying performance with an enhanced flow rate such as with a 2.5 GPM showerhead.) 

Firstly, you’ll love the ultra-slim design, which is only 2.3 inches. Secondly, I swear, it’s the only under sink water heater that will allow you to install it in any suitable placement twisting 360 degrees.

The temperature is presentable at any point between 67℉ to 116℉, and the LED will show that. Or you can set the temp on 104℉ with a single touch on a dedicated button. Both the default control panel and the remote control device contain a touch panel.

The unit draws 22~25 amps current during operation, and you will require a 10 AWG hardwire connection in line with a 30 amps circuit breaker. However, you will need 1/2 inch NPT water line connectors to hook it.

Very Important Parts to Note!!!

Limited Flow Rate

The unit provides the best performance at 1 GPM flow rate or MAXIMUM in 1.5GPM. So, I will highly suggest you install a 1.5 GPM aerator at your sink faucet. 

It’s not eligible to handle a showerhead or anything with that higher flow rate. Additionally, the inlet water temperature affects its performance. 

Performance Demonstration According to Our TESTED RESULT

(The accuracy might be ±3℉)

When the Flow Rate Remains 0.7 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+62)

When the Flow Rate Remains 0.8 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+57)

When the Flow Rate Remains 1 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+49)

When the Flow Rate Remains 1.2 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+42)

When the Flow Rate Remains 1.5 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+37)

Finally, the unit is around 98% energy efficient, and by implementing intelligent modulation technology automatically, it adjusts the power according to water flow. Ecotouch is ETL certified, very safe to use, and remains protected from any dry startup.

Note: All the settings go reset if the power goes off.

5. Best Tank-Type with Fastest Recovery Rate – Stiebel Eltron SHC 2.5

  • Tank Size –  2.5 Gallon
  • Recovery Rate – 18 minutes Only!
  • Power – 1300 Watt
  • Temperature Range – 86°F – 140 °F
  • Warranty – 6 Years for Tank
  • Water Inlet/Outlet Pipe –  1/2 inch NPT

Stiebel Eltron SHC 2.5 raises water temperature faster than all other tank type under sink water heaters that we’ve tested before writing this review. 

However, Stiebel Eltron is a European brand, and the SHC 2.5 models are entirely manufactured in Germany.  

How is their performance outstanding? 

Well, Stiebel Eltron has engineered the model, ensuring the “best insulation,” “most optimized heating elements,” and most importantly, the “advanced heat exchanger.”

As a result, energy losses remain almost zero, and the water temperature gets raised to MAX almost instantly and remains hot for practically 20+ long hours.

But, you might be shocked to hear that SHC 2.5 consumes the lowest electricity among all, which is only 1300 watts! (All the rests are 1440W). So, no breakerno special wiring is required. Only you need to plug and play! 

Our Impressive Testing Experience and some FAQs

How much it takes to heat the full tank of water?

Stiebel Eltron claims the 2.5 Gallon unit takes around 18 minutes. Though practically we’ve found extremely hot (140°F) water within 7 Minutes! It was spring in Arizona, and the inlet water temperature was around 61°F.

For sure, in winter, it will take longer.

The shape seems weird. Will it be set under my sink?

Here are the dimensions

2.5 Gallon Variant = 18(H) x 11(W) x 10(D)

4 Gallon Variant = 19(H) x 12(W) x 12(D)

6 Gallon Variant = 20(H) x 15(W) x 15(D)

Generally, all American Kitchen cabinet has 26-inch clearance under the sink. So all the variants will fit nicely, and as the thermostat regulator remains at the tip, you won’t need to bow too much to control the temperature. It’s an advantage for sure.

Can I plug it into the same socket of Refrigerator/Garbage Disposal?

You can plug in this 1300 watt under sink water heater with a Garbage Disposal without any circuit breaker. But not with a refrigerator.

 Stiebel Eltron SHC 2.5 draws around 11.3 amps load, which is okay for any 15A random socket. To increase the load along with other appliances, you’ll require a breaker.

Can I use it inside RV?

There’s no reason why you can’t if you have access to a 110V 15A electric outlet. For RV uses and other recreational purposes, it’s best to use it as a primary water heating solution.

Note:  I highly recommend the 6 Gallon Unit for taking a shower, in case you want to.

Finally, the customer support of Stiebel Eltron is outstanding! So, from every single aspect, SHC 2.5 is an excellent choice for me.

6. “Editor’s Choice” 3 GPM Tankless Water Heater – EcoSmart ECO 11

EcoSmart ECO 11
  • Flow Rate – 1.3~3.1 GPM
  • Temperature Range – 80˚F – 140˚F
  • Power – 13 KW
  • Wiring – 60 amp Breaker + 10 AWG cable.
  • Warranty – Lifetime for Parts!!!, Labour Fee Not Included

The only Under Sink water heater that will last for a lifetime… It’s the most simple sentence to explain EcoSmart ECO 11.

But the condition is, you need to install the unit by a licensed technician.

However, it’s not that expensive at all !!! 

By the massive 3.1 GPM flow rate capacity, the unit can handle the entire kitchen or one entire bathroom, including sink, toilet, showerhead, and bathtub. Also, the outlet temperature is too much satisfying! I will briefly explain with a temperature chart.

The unit is Energy Star certified and around 99% power efficient. Temperature is adjustable between 80°F to 140°F, and you are allowed to choose any scale between C/F by pressing the regulator knob for 3 sec. 

An only single drawback is that you will require strong electric wiring throughout your house; otherwise, some users have experienced bulb flickering during operation. But less than 0.5% of users face this trouble. 

Our in Brief Testing Result

Firstly, The Unit requires a 1/2 CF fitting water inlet, hard electric wiring with 6 AWG cables, in line with a 60 amps breaker.

We’ve tested the ampere when the unit remains on MAX setup and water flows by 3+ GPM; it consumes about 54~57 amps of current. 

Accordingly, the hourly cost remains between $1~$1.5 per hour if it stays on power continuously. So, by random daily uses, the monthly operational expense will be around $40-$60, depending on the seasons.

Here’s Our Test Result on Several Flow Rates

(The accuracy might be ±2℉)

When the Flow Rate Remains 1.3 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+65)

When the Flow Rate Remains 1.75 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+60)

When the Flow Rate Remains 2.2 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+52)

When the Flow Rate Remains 2.7 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+45)

When the Flow Rate Remains 3.1 GPM

If the Inlet Temperature is X, The outlet temperature will be (X+40)

Finally, we’ve interviewed several users and asked them about their experience with EcoSmart’s customer service. Unfortunately, most of them aren’t much satisfied with the helpline while facing any issue or need to troubleshoot. Otherways, everything else is fantastic.

7. Best QualityThermostat with Anty Freezing Function – Camplux ME25

  • Tank Size –   2.5 Gallon
  • Recovery Rate –  6.8 GPM
  • Power – 1440 Watt
  • Temperature Range – 50°F – 140°F
  • Warranty –  1 Year Warranty
  • Water Inlet/Outlet Pipe –  1/2″ NPT

If you are too serious about the temperature accuracy, then Camplux ME25 could be the unbeatable solution. 

Accordingly, this item is only the best for colder areas where the temperature might fall significantly, and appliances fall at risk of getting frozen damage.

Additionally, in terms of energy efficiency, Camplux is one of the toppers. If you use it too heavily and regularly, the yearly electricity bill won’t be more than $88, which is proven.

You may have noticed that its shape is quite exceptional. So here’s the advantage, instead of hanging with a mounting bracket, you may simply place it on the floor. 

1.3, 2.5, and the 4-gallon variant require a 1/2 inch NPT female water line, and all these models contain a power plug. All you need is to plug it in and tap it with a water line, and the heater will be ready to deliver on-demand hot water.

An impressive advantage, Camplux has used glass lined water tank instead of stainless steel. Which is very long-lasting and helps the hot water to remain hot for a longer duration. (More than 16 Hours)

User Experience Based on Our Interview


A drawback is, the power cord is only 2-feet long. So, either you’ll require an extension cord or a new power socket installation. 

All other procedures are straightforward; only you need to ensure the water line connections and plug in the unit.

Note: Camplux claims that the warranty will be void due to DIY installation if you are not a licensed plumber. In most cases, user’s don’t care about that 1-year warranty and go for DIY. I would recommend you to do the same if there’s no shipping damage and you feel confident enough.

Heating Duration

Camplux claims the recovery rate is 6.8 Gallon per hour. In practical operation, if the inlet water temperature remains around 60F, within 10-12 minutes, the temperature climbs to the MAX point.

Thermostat Performance

The thermostat regulator has 5-different pointers, and here’re the temperature ranges.

  • Anti Freeze
  • 1- Up to 77°F
  • 2 Up to 95°F
  • 125°F
  • Max (140°F)

The important fact is, the unit is called the Beast of Thermostat cause after years of use, the performance remains like the new. (We’ve ensured that interviewing multiple users.)

8. Best For DIY Under Sink Installation – Eemax EEM24013

Eemax EEM24013
  • Flow Rate – 1.3~3.1 GPM
  • Temperature Range – 80˚F – 140˚F
  • Power – 13 KW
  • Wiring – 60 amp Breaker + 10 AWG cable.
  • Warranty – 1Years Parts, 5 Years Leakage.

If you prefer DIY installation for your under sink water heater rather than highering a plumber or electrician, then Eemax EEM24013 would provide all advantages you need. Cause, 

  1. The unit comes with everything for installation; you just need to screw things up.
  2. DIY installation won’t void the warranty. Stay worry-free! 

Let me reveal a Secret! 

Eemax EEM24013 is precisely similar to the EcoSmart ECO 11, with a different branded chassis. Both of them contain the same quality, performance, durability, functionality, and internal components.

The only difference, ECO 11 comes with a lifetime warranty with the condition that you have to install it by an authorized dealer. On the other hand, Eemax has no conditions, but the warranty period is limited.  

Maybe you’re getting worried about the limited warranty period. But we’ve interviewed almost 20 users; they haven’t faced any issue after 1-years of trouble-free operation. However, any built-in defect/carrying damage that’s instantly replaceable within the warranty period.

Features and User Experience

Eemax can produce hot water up to 120°F with a 1.5~3.1 GPM high flow rate. However, it’s selectable between 80°F to 140°F. You won’t get more than 105°F output with a higher flow rate, which is decent, though!

Importantly, you can get rid of the primary hot water source depending on it for the whole kitchen or bathroom, including all your faucets and showerheads. 

Installation requires hard wiring by 6 AWG copper cables in line with a 60 amp breaker and 1/2 inch female hose pipe for the waterline.

Features and Safety

  • Dry startup protection
  • ETL certified and overheat protection
  • C/F Temperature Scale Conversion
  • LED with White Backlit 

Finally, Eemax EEM24013 is a comparatively large tankless water heater, so that I won’t recommend it for a single sink. 

Instead, if you require a hot water supply for the entire bathroom as well as the sink or for the whole kitchen, including sink, dishwashers, and other appliances, then it’s a great choice.

9. Best for Commercial Sink – Thermomate ES700

thermomate ES250 2.5
  • Tank Size –  6.5 Gallons
  • Recovery Rate – 6.8 GPH
  • Power – 1440 Watt
  • Temperature Range – 50°F to 149°F
  • Warranty – 3 Years for Tank, 1 Years Parts
  • Water Inlet/Outlet Pipe –  1/2″ Male NPT

All under sink water heaters aren’t suitable to handle commercial loads. Accordingly, you’ll love to save some bugs in picking a water heater for bars, salons, spas, hospitals, garages, RVs, and other commercial institutions.

So, we’ve found Thermomate ES the most proper unit to fulfill all commercial criteria with the lowest price tag.

Thermomate ES is very similar to the “Camplux ME” series, and all the functionality and internal components are almost the same. Though it’s a little bit heavier, and we’ve experienced slightly better performance in several aspects. 

Notably, the warranty, customer support, along with the sturdiness, are far better than Camplux ME (with a better price).

Finally, Thermomate has attached 

  1. Stainless steel built, corrosion-resistant heating element 
  2. Glass-lined enamel coated tank
  3. Gold porcelain lining insulation 

The water temperature rises too fast for all these arrangements, and unused hot water remains hot for around 18 hours.

Few User’s Experience

Installation: Thermomate comes with 4-different variants, and only the 1.3, 2.5, and 4-gallon models contain a power plug, and the 6.5-gallon unit requires hard wiring. 

All variants require a 1/2 inch NPT water line, and the mount brackets are included with the packaging. Circuit breaker isn’t necessary for none of these models.

Performance: Here’s the fact that you should note down. All these units are 1440 watts, so the 2.5-gallon unit will heat faster than the 6.5-gallon variant. 

We’ve physically tested the 4-gallon model from a user, and it took around 18 minutes to become thoroughly heated. 

Notably, the max temperature of this sink water heater is around 150+ degrees Fahrenheit, which is higher than all others else on this list.

Energy Consumption: Here, the unit falls behind other competitors. On random uses, the electric bill costs yearly $90+ which is slightly higher than other models.

If you are concerned about power efficiency, I will suggest the “Ecosmart ECO Mini,” to be satisfied.

10. Energy Star among All Tank-Type – Ecosmart ECO Mini

Ecosmart ECO MINI 2.5
  • Tank Size –  1 Gallon/2.5 Gallon/4 Gallon
  • Recovery Rate – 6.8 GPH
  • Power – 1440 Watt
  • Temperature Range – Up to 150˚F
  • Warranty – 6 Year Tank, 2 Year Parts
  • Water Inlet/Outlet Pipe –  1/2 Inch NPT

EcoSmart, the American brand, has devoted its entire focus to minimize energy losses and give a massive boost to power optimization. So, they are currently the #1 Energy Star with an ultimate rating of 99.8% efficiency.

EcoSmart comes with 1/2.5/4/6 gallon variants, and all of them consume 1440 Watt in MAX power setup. But, while taking a full shower, the unit consumes only 100 to 140 KWh each hour. (Detail Explained in Test Result)

The unit contains a power LED with a heating LED which is missing in 90% of the under sink water heater. However, the thermal regulator is straightforward and explicitly contains a 125F and MAX pointer on it.

Our Testing Result

How much it takes to heat the water?

Our test results in Arizona, where the inlet water temperature was 61°F, the 2.5 gallons Under Sink Water Heater took around 7 minutes to reach 125°F. If you set the regulator on MAX, the temperature will climb at around 141°F.

Note: As all size variants are of the same wattage, so, 1 gallon will take around 3.5 minutes, 4 and 6 gallons will take accordingly 14 and 20 minutes to heat the whole tank of water.

How much electricity does it cost?

We’ve tested the 2.5-gallon unit with a meter while taking a shower. The meter reading picked only 0.090 KWh impressively!!! So, the hourly cost remains around 0.012 USD. Of course, in winter it will rise two times.

So, the monthly electric bill for EcoSmart Mini will remain around $60 to $70.

What’s About Installation?

I don’t know why Eco Mini doesn’t come with any instruction guidelines! The unit contains a 1/2 inch NPT water connection, but no hose line is included in the packaging. 

So, if your faucet line is 3/8 inch, then you’ll require a hex nipple converter.

Electric connection is nothing complicated; simply plug-and-play installation. No circuit breaker is required at all.

11. Best Water Heater for Utility Sink – Stiebel Eltron DHC 8/10

Stiebel Eltron 224201 240V
  • Flow Rate – Up to 1 ~ 3.2 GPM
  • Temperature Range – 80˚F – 140˚F
  • Power – 8/10 KW
  • Wiring – 50 amp Breaker + 10 AWG cable.
  • Warranty – 3 Years Labour and Parts

Stiebel Eltron DHC 8/10 could be an intelligent choice to flow unlimited hot water to your utility sink with the highest reliability in the tankless world. 

There’s a ton of reason to prefer Stiebel Eltron as your daily gadget. It’s an Origin European Brand, and the unit is entirely designed and manufactured in Germany. 

However, their heating elements, heat exchanger, and electronic mechanisms have been evolved to extraordinary, being the most optimized, fastest heating, long-lasting and perfect.

Our Interviewed Users Experience 

How is the heating experience?

“Its phenomena!!! The unit is programmable between 86F to 140F, and it can sense the water flow. If you preset the temperature to 90F, DHC 8/10 can supply it with around 2.5 GPM water flow. (to a large sink faucet). Which is more than sufficient temp for washing hands, cleaning dishes, and whatever else you want. 

The unit can handle a large shower head at a lower temperature. 

Notably, the DHC 8/10 maintains the temperature super constantly by power reduction/increasing when you change the water flow. 

What’s about installation? 

It’s tricky for sure… The unit requires a 50 amps breaker along with 8 AWG copper wires and a 240V electric connection. 

The unit contains 1/2″ MIP water inlet/outlet, and I’ll strongly recommend installing a 2.5 GPM aerator to get a satisfactory performance.

Can I use it in RV?

Mostly No, Except your RV contains a 240V 60amps capable outlet.”

Finally, Stiebel Eltron’s customer support is better than any other else. So the warranty and any issues

Essential Guidelines for Under Sink Water Heater

1. Some Brand Suggestions to Choose

When there’re too many brands with multiple offers and functionalities, getting confused is too easy to make a decision. So here’s my simple guideline to follow.

In Case you need a DIYer Friendly Unit.

DIYers require all parts for installation and mostly a condition-free warranty so that it won’t get void due to your self-installation. 

So, Stiebel Eltron, Ariston Andris, and Eemax are the most preferred brands for you. 

Cause, firstly, they all bear too much responsibility for their consumers and in any installation/operation difficulties you won’t need to be held on a call or hear something unsatisfying.

Secondly, they won’t deny your warranty due to DIY installation, or no need to hire a licensed dealer/plumber with expensive wages.

Finally, all their fittings are too available nearby (Mostly 1/2 inch NPT), and they all come with detailed installation guidelines. 

However, for a tank-type water heater, I’ll highly suggest the Ariston Andris and Stiebel Eltron or Eemax for the Tankless unit.

In Case you want Warranty Assurance.

Rheem and EcoSmart will be the best preference in this case. 

Importantly, EcoSmart comes with a lifetime warranty for a tankless water heater, though the labor cost isn’t included. But Rheem pays for labor with their 1-year parts and 5 years heat exchanger warranty.

In Case you want Gorgeous Design and Smart Operation.

Ecotouch is the champion from this category. Their slick and slim design will make you pleased, and it comes with the most advanced touch control panel with LED and gives your sink a refined look.  

In Case your demand is available sphere parts for repairability.

Bosch and Bosch is the only option for you. This is the most popular tank type under sink water heater among the entire United States. There are no components inside it that you can’t replace, including the heating elements, thermostat, or anode rod. 

But, their customer support is irritating. So if you are highly confident about the mechanism and able to repair it by yourself without seeking help, then it might be the perfect option for you.

2 Tankless or Tank-Type what should I choose?

Shortly, underpowered tankless water heaters that are suitable for Under Sink installation can’t supply hot water with a HIGHER flow rate. Yes, they can, but the water will be LUKEWARM in that case. 

So, if you need unlimited hot water flow but LUKEWARM water is okay for your task; however, a higher voltage electric wiring won’t be an issue, then you may go for tankless models.

On the other hand, the tank-type water heaters offer limited hourly hot water production, but they raise the temperature almost towards the boiling point. 

Generally, for washing hands, both tankless and tank types are okay. 

But tank-type models are highly recommended for cleaning dishes cause you’ll require boiling water to wash oily dishes adequately.

3. Inline Installation vs. Individual Installation – Advantages and Drawbacks

What’s your water demand for the sink? Is it too high? 

In that case, installing the Under Sink Water Heater in line with the primary water heater should be the best preference.

Advantage of Inline Installation

The inline installation will cut the waiting time during hot water uses. Additionally, there won’t be any water wastage. 

However, this setup can provide a massive amount of hot water with the highest temperature.

So, it’s best for kitchen sink or bathroom sink where the demand is higher.

Drawbacks of Inline Installation

Mostly, you’re running two water heaters at a time, though it won’t increase your electric bills. But due to High Ampire Consumption, your home wiring will be at a heavy load.

It won’t be an issue at all if your home wiring isn’t too old and of low quality.

Secondly, if the primary water heater gets rusty and passes hot brown water to the under-sink unit, that’ll be an attack on its life span.

If You don’t Need a High Amount of Hot Water for your Sink

Then go for Independent installation. Mostly I preferred this setup for the utility sink.

Advantage of Individual Installation

Your primary water heater and home wiring will remain out of load. Rusty old primary water heater won’t destroy the under-sink unit.

Drawbacks of Individual Installation

You won’t get a massive amount of hot water for a tank-type unit, and the temperature will start falling gradually when the faucet remains on.

4. Under Sink Water Heater Operational Cost – Tankless Vs. Tank-Type

Here’s the straightforward monthly running cost calculation.

Operational cost of Tank-Type: 95% tank-type water heater from the under-sink segments comes with 1440 watt heating element. 

Hourly you’ll highly require 5 gallons of boiling water, and the unit will take 18 minutes to prepare it. So the Unit (KiloWatt Hour) calculation will be like

1.440KW x 0.33 Hour = 0.475 Unit 

[Here, 1440 watt = 1.44 KW & 18 min = 0.33 Hours]

So, the hourly electric bill will be around 0.475 x 0.1339 = $0.0636 Only.

[Electricity cost is $0.1339 per unit]

If you use the appliance for 3 hours each day, the monthly bill will be around…

0.0636 X 3 X 30 = $5.72 Only!!!

 Depending on the season, the cost may increase/decrease slightly, and on average, the yearly electric bill remains around $60 by everyday use.

5. Operational Cost of Tankless Units

A tankless water heater heats water faster and comes with 5.5KW to 13KW based on the water flow rate capacity.

So, here’s the easiest equation for cost calculation.

P (KW) x H (Daily time of using) x 30 (Days) X 0.1339 (Electricity Cost)

If you install a 13KW unit and runs it for 1 hour a day (More than Enough), the monthly cost will be around.

13 x 1 x 30 x 0.1339 = $5.22 Only.

Lower powered units such as 5.5KW will need to run for a longer duration than the 13KW.

On-Average, the yearly electric bill won’t be more than $60~$70 in MAX.

Note: Installing under sink water heater reduces the load of the primary water heater. So, in the end, it reduces the energy cost instead of increasing it.

6. A Few Tips for Long Time Users

If you can ensure a few DIY maintenances, the under sink water heater will last for decades.

Keep the Tank/Heat Exchanger Clean: Boiling water releases various minerals that get attached to the water tank and heating elements. As a So, the performance drops dramatically, and leakage appears in the long run. Accordingly, it increases the electric bill twice.

To get rid of it, clean your water heater with Apple Cider Vinegar at least once a year. 

You may choose the lowest-cost apple cider vinegar; quality isn’t a fact here.

Simply mix them with 2X amount of water (for the tankless unit, use it directly) and pour inside the tank using a Shipon Pump.

Leave it for 1 hour and drain it gently. 

Before you connect with the electric line, flow water through it for five minutes. You may see some dirty water which is okay. 

Then it’s ready to use.

Use Low Flow Aerator

I would highly recommend a 1 GPM aerator for the kitchen and utility sink for both tankless and tank-type units. 

For the bathroom, you may go for 2.5 GPM.

It will enhance the performance of the tankless model and reduce the load of heating elements. Accordingly, the aerator will resist the drastic temperature drop inside the tank-type model, and the tank won’t get cracked due to a sudden temperature fall.

Don’t Use at Max it in Max Power.

It’s only applicable for Tankless models. Using the unit with 80% power will run the heating coil more efficiently. Also, it will enhance the lifespan impressively.

7. Customer Support of Different Brands

Here’s my top to bottom customer support rating, then I’ll discuss why I’ve given like it.

  • Stiebel Eltron – 9/10 (DIY Friendly)
  • Ariston Andris – 9/10 (DIY Friendly)
  • Rheem – 8/10
  • Eemax – 8/10
  • Thermomate – 7.3/10 (DIY Friendly)
  • EcoSmart – 7/10
  • Ecotouch – 6.5/10  (DIY Friendly)
  •  Camplux – 6/10
  • Bosch – 5/10

Maybe you’ve been shocked to see that I’ve marked Bosch and Camplux at lower due to their quality of customer support, but it’s the reality.

Bosch and Camplux are both too famous brands in America, but their support is just not satisfying.

However, I’ve noted which ones are DIY friendly, so if you are a DIYer, you only should pick one of them.

8. Electrical Wiring Guide For Undersink Water Heaters

Wire Gauge: 

Copper 12 AWG wire is sufficient for most tank-type water heaters (1, 2.5, 4 Gallons), which are 1440 watts.

If the unit is 2000 watts, then I’ll suggest going for 10 AWG copper cables. 

For the 240V tankless under sink water heater, here’s the data chart.

5.5KW – 10 AWG

6KW – 10 AWG

8KW – 8 AWG

9KW – 8 AWG

10KW – 6 AWG

11KW – 6 AWG

13KW – 6 AWG


1440 watt tank-type heaters don’t require any breaker. But for a 2000 Watt tank-type heater, a 20 Amp breaker could be installed.

For the 240V tankless under sink water heater, here’s the instruction for breaker installation.

5.5KW = 30 Amp

6KW = 30 Amp

7KW = 30 Amp

8KW = 40 Amp

9KW = 40 Amps

10KW = 50 Amp

11KW = 50 Amp

13KW = 60 Amp

9. Can I install it inside RV?

You can install 1440 watt tank-type under sink water heater inside your RV and the Dynamo won’t face any extra load for that.

Or, if your Dynamo isn’t too strong, you may install the Stiebel Eltron SHC 2.5 tank type model, which is 1300 watts only.

But, if you want a tankless water heater, in that case, you’ve to make sure the RV has a 240V outlet, and it’s capable of supplying 40 Amp current. In that case, you may install the Ecotouch 5.5KW model for a tankless experience.

10. What to do if water comes out brown from a Tank-Type Heater?

Firstly, check your cold faucet to ensure that no brown water is coming through the pipeline. If that’s okay, then detach the water lines and drain the tank first. 

Then replace the anode rod, and clean the heating element gently using vinegar. Finally, clean the water tank gently with apple cider vinegar until it becomes rust-free. 

Now it’s ready to work again.

11. Steps for Anti-Freezing Protection.

If you remain at home, keep your heater on power and slightly twist the thermostat to an anti-freeze position or any MINIMUM point.

But, if you need to leave home for an outing for few weeks, then ditch the water lines and drain the waters. If your tank is too heavy, you may use a siphon pump that can reach inside the waterline. 

Then pour some antifreeze agent inside the tank, and you are good to go!

12. Can I use it for a Bidet?

Definitely, you can!!! 

But, be aware of the temperature in case you are using a tank-type model. Cause their MAXt temperature limit is too high, and you can’t get that in touch. 

13. Can I drink hot water from the Under Sink Water Heater?

No, I won’t suggest you do so. For drinking purposes, you’ll require instant hot water dispensers.

14. What’s the functionality of the pressure relief valve of Tank Type Heaters?

Tank-type water heater contains a pressure relief valve to release the internal pressure that creates due to hot water bubbles. Practically, you won’t need to do anything with that or even touch it at all. It’s an automatic mechanical procedure like your pressure cooker. 

But, you may tap an overflowing pipeline there, which is optional.