Best Indirect Water Heater in 2021: Complete Reviews

It may have become hard to make a proper choice when it comes to water heaters. For that reason, we’ve taken it upon ourselves to write up an article to help you find the best indirect water heater out there. Help yourself get hot water whenever you need it, and make sure you are never having to use cold water at any point, by having the best knowledge about what indirect water heater you need, and all there is to know about them!

In a Hurry? Here's Our Top Choice:

Ecosmart ECO Mini, 2.5 Gallon Indirect Electric Mini Heater

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If you don’t have time to go through the whole list, we can recommend to you our top choice when it comes to indirect water heaters, and that is the Ecosmart ECO Mini. This model has had great customer reviews, and can provide you hot water all day without fail. It also saves money in the long run and is made out of very durable materials.




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Ecosmart ECO Mini 2.5 2.5-Gallon 120v

  • Type: Tank, Indirect Electric Water Heater

  • Tank Capacity: 2.5 Gallons

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Reliance 6-Gallon Compact Electric Water Heater

  • Type: Tank, Indirect Electric Water Heater

  • Tank Capacity: 6 Gallons

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Rheem MR50245 Marathon Tall Water Heater

  • Type: Tank, Indirect Electric Water Heater

  • Tank Capacity: 50 Gallons

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Burnham AL35SL Indirect Water Heater

  • Type: Tank, Indirect Fired Water Heater

  • Tank Capacity: 35 Gallons

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  • Type: Tank, Indirect Water Heater

  • Tank Capacity: 40 Gallons

Now that you know our top choices, let’s look deep into each product here. You may end up finding the best indirect hot water heater for yourself too!

Top 5 Best Indirect Water Heater Reviews

1. Ecosmart ECO Mini 2.5 2.5-Gallon 120v Electric Mini Tank Water Heater

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Our top product for you today, this is the smallest product in our entire list of indirect hot water heater reviews, and it is pretty much covered in the name of the Ecosmart ECO Mini! As far as heating systems go, this comes in as the smallest and most compact water heater on our list, and it can dispense 2.5 gallons of hot water when needed from the water tank. However, that doesn’t make it a problem, rather it can take care of your needs when used properly.

The Ecosmart ECO Mini is an electric heater, and most of them are quite efficient. However, this water heater uses its energy very efficiently and comes in with a 99.8% energy efficiency. This not only makes the product more optimal for water heating, but it also does great at reducing the expenses for your water heating needs. You’ll get your hot water with ease, and make sure you’re wasting as little energy as possible. Being this small for a water heater must have its benefits, and that’s right, this one does. It can easily fit anywhere you need it to, and it will cause no problems. It also comes with a very easy installation process, making it very convenient.

Overall, the Ecosmart ECO Mini is definitely a good option for those who need a lightweight indirect water heater, because it can get the job done, and not take much space in your home. One drawback for this mini water heater is the need for some additional parts when installing it. It may be easy to install, but some parts may be required.

  • Very small and convenient
  • Is very lightweight and easy to carry
  • Very energy efficient
  • Has a digital display
  • Some additional parts may be required for installation

2. Reliance 6-Gallon Compact Electric Water Heater

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Next up, we have a Reliance water heater for you, and it is the Reliance 6 6 SOMS K electric water heater. This unit comes as a very compact water heater, allowing for you to fit it in most places around your home with ease. It also makes for very easy installation, which can be very convenient with this small and lightweight model.

The Reliance 6 6 SOMS K also comes with more convenient features, including the water inlets for cold water and hot water on the side of the unit, making for installation to be even easier. It doesn’t stop there though, since this model also comes with a temperature valve and pressure valve already built into the water heater, making for convenient use, and also saving you the effort of having to go through putting them in. Even though its small and has many convenient features, this water heater is still very durable, especially with the glass lining inside, making it more corrosion resistant, and allowing for a longer lifespan of the entire model. Reliance are a reputable water heater company with a good name for themselves, and you could do with checking out some Reliance water heater reviews if this product got your interest!

Overall, the Reliance 6 6 SOMS K is definitely a worthwhile investment, especially considering it is a top brand’s water heater, for a very affordable price, and it will always make sure you get hot water when you need it. The one drawback of this water heater is that its affordability made it lack the best parts, and some parts are not made of the best materials.

  • Installation is quite easy
  • Has water inlets on the side for convenience
  • Is quite small and fits in most places easily
  • Very affordable
  • Some parts are not made of the best materials

3. Rheem MR50245 Marathon Electric Water Heater, 50 Gallon

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This next product on our list is manufactured by Rheem who are very popular for water heaters, and it is the Rheem MR50245 electric water heater. You’ll see that this unit comes with a very sleek and aesthetic design, while also being quite small and lightweight. This allows for you to integrate it into your home with a lot more ease, and without much to worry about.

The Rheem MR50245 also comes with a built in thermostat which uses a thermometer to accurately measure the temperature of the water, so you always know exactly how hot your water is before you use it. While being very lightweight, it is also very easy to set up and install, making this a very convenient model overall. Not only that, but despite its low weight, it is also very durable. It is made out of cast iron, giving it a sturdy and durable base to last you years and years. Being an electric water heater, it is very efficient and in the long run will help you decrease your energy bills.

Overall, the Rheem MR50245 is definitely one of the best units out there, and you can definitely look into it. It also has a very convenient technology to help you keep track and control the temperature of the water heater for whenever you need to make any adjustment. With its extensive use of different features, this water heater is a bit expensive, making this the one drawback. 

  • Great design with convenient build
  • Made of cast iron and is very durable
  • Very accurate temperature display
  • Has very high efficiency
  • Quite expensive

4. Burnham AL35SL Indirect Water Heater, 35 Gallon

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The next Burnham AL35SL Alliance SL water heater in our list, which is an indirect fired heater. This water heater will last you for a long time, thanks to the hydra-stone lining on the tank. This helps the tank fight against corrosion for a longer time, giving the tank itself a longer lifespan.

The Burnham AL35SL Alliance SL already comes with a strong lining, but it is also made out of stainless steel, giving it even more resistance against common problems that water heater tanks face. The tank itself comes with a capacity of 35 gallons of water, making it quite easy to get your hot water needs completed. As for the heating, the unit comes with a heating coil, making it all the more convenient for you. The mechanism of this water heater is so efficient, that it will end up saving you money in the long run, by dropping your water heating bills down. Not only will you be able to heat your water better, but you’ll also be able to keep its temperature higher for a longer period of time. The tank comes with insulation that helps the water retain its heat for a longer time.

Overall, the Burnham AL35SL Alliance SL is definitely one of those heaters that you could definitely look into. It is quite affordable, so most people can look into this. It’s also very convenient and will allow for easy installation in your home. One drawback for this unit is that it comes with only one tank size.

  • Hydra-stone lining to be corrosion resistant
  • Comes with a heating coil
  • Is very efficient
  • Easy to install
  • Does not have multiple sizes for tanks

5. BIC IBC40 Indirect Water Heater, 40 Gallon

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From the very reputable brand of BIC, comes this product; BIC IBC40. This is a very durable unit, which is made out of 316l stainless steel, giving it a long lifespan, in terms of a strong build. It also comes with a thermoplastic jacket, and this helps it fight off against corrosion, making it a good investment.

The BIC IBC40 also has a good build in order to make sure the hot water you get stays hot. This is done by a layer of insulation which is thicker than 2 inches, making sure that the product retains its heat, and keeps the water at your preferred temperature. This is also helped by the good water temperature sensor built in the tank. This allows for the product to maintain the temperature of the water by optimizing the machine in the water storage. It is also energy star certified, assuring you that this is a product which is friendly for the environment, and is also quite energy efficient.

Overall, the BIC IBC40 is definitely a good choice for you, especially if you have a medium to large sized home. The 40 gallon unit will manage to be a good indirect heater for your home, while also being optimized to last for years and years. It also comes with a first hour rating of 193 gallons per hour at 140F, making it a worthwhile investment. One drawback for this unit is that it comes with a hefty price when compared to other units.

  • Uses strong stainless steel in build
  • Is quite energy efficient
  • Energy star certified
  • Has an insulation which is more than 2 inches for storage water
  • Comes with a hefty price

What Are Indirect Water Heaters?

Indirect water heaters are very energy efficient water heating systems. They work with multiple types of water heaters. Once placed in the water systems of your house, they use a furnace or water boiler to heat the water. They can be used with any of gas, propane, solar electric water heaters, and etc. However, you can’t use an indirect water heater with a tankless water heater. They require tanks, and based on the size of your tank and house, you can supply hot water all throughout your house without much of a problem. 

How Do Indirect Water Heaters Work?

Indirect water heaters themselves use no power, rather they use the mechanism of heat transfer via the heating coil inside. Most modern homes have a space heating system installed already. That’s where you install an indirect water heater system. This heat is then transferred into the coil of the indirect water heater, which then works to heat the water up in your water storage. The stainless steel tank that a lot of water heaters use, works well to retain most of the heat in the water, and help keep your water hot.

Thus, this process is the reason why indirect water heater systems are very efficient, since they use the mechanism already built into your home, and use no added power of their own.

Factors to Consider When Buying An Indirect Water Heater


In order to use an indirect water heater, you’ll want to make sure your home supports the installation in the first place. Indirect water heaters can be used by a home that supports heating, ventilation and air conditioning systems, also known as HVAC. Most old homes don’t come with this compatibility, and if you live in a much older home, you may have to look into a different option.

Tank Size

When it comes to finding the best indirect water heater, you’ll need to know what size tank you need. You could use a very good water heater, but your house might be too large in order for its size. Thus, optimally sized tanks are a very important factor to consider when buying an indirect water heater for your home. If you get the right size, you’ll be treated to the wonderful sight of having hot water in your home at all times, without ever worrying about it. From our list of indirect water heater reviews, you can notice a varying range of sizes available, making it easier for you to choose one optimal for your house.

Insulating Capabilities

An indirect water heater will require a tank with features that allow for heat retention. Since the indirect water heater itself uses no power, there must be other features set in place to best help it keep your hot water hot. A few of the products we’ve shown have various features,which include having a stainless steel tank. There are more than a few ways to do so, so it is best to find one that can!

Video Credit: Jim Ruppert


Q. Is an indirect water heater worth it?

Indirect water heaters are a very efficient means of heating your water up for your house. While they have a little more maintenance due to the inclusion of tanks, they will still end up saving you on water heating costs, and also make sure you get continuous hot water all throughout your house.

Q. How long does an indirect water heater last?

An indirect water heater can last you for around 15-20 years. So, it’s best to get one that’s worth it in the long run. You can also rely on the warranty of the product you get, because the longer the warranty, the more help you’ll have in case anything goes wrong. Not to mention, a longer warranty means that the manufacturer has faith in the water heater lasting for a long time.

Q. How big of an indirect water heater do I need?

12-14 people should be good enough with a 30 gallon indirect water heater. This also takes into consideration how well your boiler works to heat the water. However, with a good boiler, and a good indirect water heater, you should be set to have unlimited hot water throughout your house at all times.

Q. What is the best indirect water heater?

As we’ve already mentioned in our article, we feel that the best indirect water heater is the Ecosmart ECO Mini model. It comes with great features that help you receive hot water when you need it, and it can last for a very long time.

The Takeaway

Hopefully you’ve come to a decision on indirect water heaters, and have managed to choose the best indirect water heater for yourself. We’ve set you up with our favorite choice out of them all, but you’ll need to make the final decision based on different factors. Make sure you have the correct heating system first, in order to make it work, and remember that they don’t work for a tankless water heater. Indirect water heaters can easily provide you with hot water all day, but make sure you choose the right type of water heater, and that the first hour rating, stainless steel tank, and other factors are present in order to help create the best water systems in your home. Whether you want a 40 gallon tank or a 50 gallon tank, it’s all up to you. Good luck looking through indirect water heaters to find the best hot water heater for yourself!

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