Best Under Sink Mini Heaters For On-Demand Hot Water

Gary Johnson
Written by
Last update:

If you want to have a constant supply of hot water on demand, one of the best solutions is a hot water heater heater.

This will come in handy if you have anyone who loves a long shower, or if you’re in a drought-stricken area where the tap water temperature is a tad low.

You probably already know that having a tankless water heater is a great choice for a number of reasons. Indeed, there are small tanks that are billed as tankless and can heat water on demand, but they are not exactly as efficient at heating water.

That said, they are a good option for a few important reasons.

Some people don’t like the look of traditional hot water tanks, which do not blend well with the rest of the decor.

Some people want to have constant hot water on demand.

Some people don’t want hot water heaters that make noise, as they stay at home when the family is at school or work.

Some people want to save money by having lower utility bills with tankless water heaters.

So, what is the best under sink mini heater?

NameCategoryProduct
Bosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-GallonBest OverallBosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-Gallon
Thermoflow UT10 2.6-Gallons Electric Mini-Tank Water HeaterBudget PickThermoflow UT10 2.6-Gallons Electric Mini-Tank Water Heater
Reliance 6 2 SSUS K 2.5 Gallon Electric Water HeaterUpgrade PickReliance 6 2 SSUS K 2.5 Gallon Electric Water Heater

1. Bosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-Gallon

Our rating: 9 / 10

Bosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-Gallon

Check Price on Amazon

Pros:

  • It’s just the right size for your under-sink needs
  • It comes with a sensor that automatically turns the unit on and off as required
  • This tankless hot water heater comes with a slim design and effectively conserves space
  • This model is suitable for a household of two to four people
  • It’s easy to install and extremely safe to use

The Bosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-Gallon (ES2.5) is our top pick for the best under-sink mini water heaters for a bunch of reasons.

Firstly, this unit is one of the most affordable, while still delivering the same amount of performance as the high-end models. It comes with a compact design that fits just right under your sink. This tankless electric water heater can deliver hot water to faucets and taps. It’s ideal for family homes and small bathrooms.

One of the key benefits of this unit is that it comes with a sensor that automatically turns the unit on and off as required. This means you don’t have to wait for the water to get hot and will always walk into a toasty shower.

2. EcoSmart ECO 11 Electric Tankless Water Heater

Our rating: 8 / 10

EcoSmart ECO 11 Electric Tankless Water Heater

Check Price on Amazon

Pros:

  • Instant hot water
  • Affordable
  • Well-rated
  • Easy to install
  • Fairly compact in size
  • Instantaneous water
  • Can be installed on the ceiling or wall

Shortly, we’re going to think about the best tankless water heaters for on-demand hot water. But –before that, if you have a large family, you’re going to need a large water heater. This is because, with a large amount of people, you’re going to be using quite a lot of hot water.

Oftentimes, the reason families opt for a tankless water heater is because these types of heaters don’t fill up with water and if you don’t need hot water, they’re not taking up space. They also tend to run more energy-efficiently than tank heaters.

The EcoSmart ECO 11 Electric Tankless Water Heater is our top pick in this category because it’s a fairly affordable and high-quality electric water heater.

3. InSinkErator HOT150

Our rating: 8 / 10

InSinkErator HOT150

Check Price on Amazon

Pros:

  • Can heat up to 23 gallons of water – more than anyone else on the market
  • Made in the USA
  • Long cord
  • Easy to install
  • Easy-to-use controls

Cons:

  • Expensive
  • Should only be used in sinks with drain lines

Manufactured by InSinkErator, the HOT150 is a galley-style sink water heater with a 150 watt rating. It plugs into a standard 120v wall outlet, it’s easy-to-use, and it comes with a patented thermo siphon system that runs quietly (or not) to keep your sink water toasty, whenever you need it.

The HOT150 can heat between 2.5 and 23 gallons of water. This means if you have a smaller sink your options are a little limited, while you have the most flexibility with a large sink. The unit uses a 1500 watt power supply (included) while larger units require a 2000-watt power supply.

Speaking of power supplies, this device features a 12-foot power cord for quick and easy installation, along with a self-resetting circuit breaker. The on/off power switch is conveniently located on the side of the unit and features an LED indicator light.

4. Stiebel Eltron 233219 2.5 gallon

Our rating: 8 / 10

Stiebel Eltron 233219 2.5 gallon

Check Price on Amazon

Pros:

  • Small, lightweight and portable
  • Low wattage and great price
  • Easy to install and use
  • Heat up water in a matter of seconds
  • One of the best under sink heaters for the money

We chose the Stiebel ELTRON SHC Electric Water Heater as our top pick for on-demand hot water because of its outstanding performance, durability, and budget-friendly price.

The compact cylindrical design of this electric water heater not only makes it easy to store but also saves space in your under-sink area. This water heater features a stainless steel construction that not only makes it durable but also gives it a clean and sleek look.

The device also comes with a digital thermostat that has three temperature settings and allows you to choose your desired temperature. The heating element is made from high-tensile aluminum which is also known for its strength and is renowned for not rusting or corroding easily.

5. Camplux ME25 Mini Tank Electric Water Heater 2.5-Gallon

Our rating: 8 / 10

Camplux ME25 Mini Tank Electric Water Heater 2.5-Gallon

Check Price on Amazon

Pros:

  • Tank water heaters are much more reliable than instant-boil models
  • Comes with a well-designed water hose
  • More cost-effective than replacing your entire water heater
  • Low operating costs

(CAM-ME25)

Our pick is the Camplux ME25, which is suitable for providing hot water for your faucet, shower, or washing machine. This tank water heater is also great for bringing your shower water to the desired temperature quickly. It is ultra-compatible with the use of a single lever faucet, so the water doesn’t have to be wasted while waiting for it to reach the desired temperature. The ME25 mini tank heater is suitable for providing hot water for your faucet, shower, or washing machine, and it’s compatible with a single lever faucet.

The other great thing about the ME25 mini tank heater is that it uses natural gas or propane to fire up at a faster rate, making it perfect for filling up your bathtub within a few minutes. The water inlet hose and the cord plug are all part of the purchase, so you will not have to purchase them separately. The product, itself, is easy to set up and use.

6. Thermoflow UT10 2.6-Gallons Electric Mini-Tank Water Heater

Our rating: 8 / 10

Thermoflow UT10 2.6-Gallons Electric Mini-Tank Water Heater

Check Price on Amazon

Pros:

  • Small enough to fit under sinks and sufficient enough to provide constant hot water whenever you need it
  • Electric mini-tank water heaters require no plumbing as they are designed for underneath installation
  • CSA certified
  • Long life cord, high temperature, and overheat protection
  • Thermostat settings of 140˚F/60˚C
  • 120V ? 1.5kW (240v – 2.0kW)

Cons:

  • A little tricky to install
  • Louder thermostat noises

This durable little tank water heater from Thermoflow is ideal for tight spaces under the sink. They are made with superior tinplate brass and are equipped with safety features for electrical overheat protection.

The thermoflow water heater is designed for installation inside a closed cabinet as it is a non-vented tank heater. These are the best under sink hot water heaters for use in apartments or in mobile homes.

These handy little tank heaters are built to last as they have a compact, portable design that’s perfect for keeping your water warm when you need a shower. It’s easy to install and it runs on 125 volts, which means it’s the perfect fit for a standard home.

7. Reliance 6 2 SSUS K 2.5 Gallon Electric Water Heater

Our rating: 5 / 10

Reliance 6 2 SSUS K 2.5 Gallon Electric Water Heater

Check Price on Amazon

Pros:

  • Easy-to-grip, rubberized handles
  • Affordable, longer lifespan
  • Easy to install

The Reliance Mini Water Heater () is ideal for smaller sinks and bathtubs. With a 2.5-gallon tank capacity, you are likely going to run out of hot water much sooner than you would with a larger tank size. It’s good for low-capacity sinks where you only require two or three gallons of hot water at a time. It will take around ten minutes to heat up the water.

Another thing that makes this a better pick than some of the other compact heaters is that it’s easy to install. All you have to do is connect it to a GFCI-protected outlet. The water heater doesn’t have a built-in thermostat, but with the vast majority of sinks out there, you don’t need one.

If there’s one downside, it’s that these compact heaters are less durable than their industrial counterparts. You’ll typically see warranties of one to three years, but industrial models usually carry five-year warranties.

8. Ariston GL4S Electric Mini-Tank Water Heater

Our rating: 5 / 10

Ariston GL4S Electric Mini-Tank Water Heater

Check Price on Amazon

Pros:

  • Runs off standard 120 volt household electrical current
  • Perfect for small bathrooms
  • Provides immediate hot water on demand

Cons:

  • Not appropriate for large sinks or larger bathrooms
  • Expensive

At the risk of sounding overly hyped about a product, I just have to say that this under sink mini tank water heater is the perfect addition to any home. It works well in bathrooms that only need hot water at a 45-second interval.

Once you install the heater, you quickly understand how it works. It can be a bit louder than expected, but in a bathroom that won’t be disruptive. The options for under sink hot water are rather limited, but this product is a winner among its competitors.

Thanks to a built-in function that stops the heating element when the desired temperature has been reached, the unit is safe to use, and the water will never reach a dangerous temperature. The cold water enters the device, which is then heated to the appropriate temperature. Once the selected temperature has been reached, water is released from the electron gun and flows to the user as hot water.

Frequently Asked Questions (FAQ)

Are under sink water heaters any good?

While it might seem like this is a niche product, under-sink heaters are a bit more common than you might expect. They are most useful for people who live in homes with abnormally long distance piping that results in a very large temperature differential between the hot water heater and faucet. For example, a house that uses a large stone foundation.

The main benefit of these under-sink heaters is that they allow you to keep your hot water heater set to a lower setting. This reduces both the energy consumption of the heater and the amount of energy lost in the water running back to the hot water tank.

If you live in a home with a large temperature differential, this product is well worth the investment. For most people, however, the price and limited use case for this product makes it an unnecessary luxury.

What is the best hot water on demand system?

If you've ever lived in an apartment with old plumbing then you are likely familiar with the concept of using instant hot water heaters. In case you didn't, it's the idea that you bring up a pitcher of water from the supply pipe instead of waiting for a hot water tank to provide you water. It works great, but only when the water is flowing.

The best under sink gas water heaters are typically electric models that use either propane or natural gas to heat water at a variety of temperature ratings. An electric water heater can be much more energy efficient and compact when installed below your kitchen sink right. Then any water coming from that faucet is instantly hot.

It's also a handy safety feature for anyone looking to install a water heater in their garage or workshop since you're not going to have to worry about standing around a propane tank.

What is the best point of use tankless water heater?

You will usually have two to three options to consider when buying a point-of-use tankless water heater: gas, electric, or propane. We'll leave the gas vs. electric debate to the comparisons section below. However, if you choose a propane tankless water heater, you will have the advantage of unlimited hot water, even at peak demand times when a limited energy source heats water to your convenience.

A large water tank that supplies hot water to all of your taps simultaneously can not keep up during peak times of demand. So, you could have lots of hot water sitting in your tank, but you would not be able to use it all. With a high COP 3-5 point-of-use propane tankless water heater, you can have virtually unlimited hot water whenever you need it [the energy source can be gas, propane, or electricity].

Why is my tankless water heater not getting hot enough?

A tankless water heater is a wonder of modern technology. It efficiently heats your household water supply at the perfect temperature while using about one-third the energy of a traditional water heater.

However, it’s extremely important to select a tankless water heater that will provide enough hot water for your needs. The smaller the home and the fewer people you will be heating water for, the less hot water you will need per person. Since most tankless heaters come with a minimum BTU rating, it is essential to ensure that the BTU rating is high enough to meet your hot water needs. Look for a tankless hot water heater with a higher BTU output than the number of people you will have using hot water (whether it’s for showers, dish washing, or other activities).

Conclusion

There are two distinct methods to heat water for cleaning, and both have their respective merits. In our guide we've covered the different under-sink heaters that work with both methods, as well as bathroom heaters that provide you with instant hot water, for when you need it. As long as you are careful to select the right heater based on your water pipes' location, we hope that you'll be able to find a suitable way to heat your domestic water supply.

Our Recommendation

NameCategoryProduct
Bosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-GallonBest OverallBosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-Gallon
Thermoflow UT10 2.6-Gallons Electric Mini-Tank Water HeaterBudget PickThermoflow UT10 2.6-Gallons Electric Mini-Tank Water Heater
Reliance 6 2 SSUS K 2.5 Gallon Electric Water HeaterUpgrade PickReliance 6 2 SSUS K 2.5 Gallon Electric Water Heater