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The Best Indirect Water Heaters for 2023

Writen by Ronald Brown

Fact checked by Natalie Bridges

The best indirect water heater is the perfect solution for any home that wants to achieve energy consumption efficiency. A high-efficiency indirect water heater keeps you warm during the cold months of fall and winter.

best indirect water heater

A cost-efficient product also provides you with significant savings during the summer. It can improve your family’s quality of life while also helping you curb energy-related expenses.

Choosing an indirect water heater can be daunting for first-time buyers because the machine looks like a conventional storage-tank water heater. You can consider these three factors to pick the top-tier indirect water heater for the family.

  • First-hour Rating: Indirect water heaters must supply sufficient hot water to family members during peak use. Although FHR varies across brands and models, your household will have more enjoyable hot water-related activities with an indirect heater possessing a high FHR value (i.e., 200 gallons vs. 100 gallons).
  • Insulation: A differentiating feature of indirect water heaters is their dependence on an external heat source. Sadly, the farther the water heater is from the boiler, the greater the heat losses. Buyers must check the storage tank’s insulation to help prevent energy losses while improving heat retention.
  • Heating Efficiency: Like direct water heaters, indirect water heaters vary in Uniform Energy Factor (UEF) values. Higher-priced units with advanced technologies often have 98% (0.98) to 99% (0.99) UEF. If the price concerns you, you can pick an indirect water heater with at least 90% (0.90) efficiency.

Picking the right indirect water heater can be challenging. This article will help you navigate through the ins and outs of choosing the right indirect water heater. Let us start with ten of the most trusted products on the market today.

Top-Rated Products

Best Overall

Burnham AL35SL


Editor’s Pick



Best Value for Money

Triangle Tube SMART80


Table of Contents

Top-Quality Indirect Water Heater Reviews

1. Burnham AL35SL Water Heater

The water heating capability of the Burnham AL35SL Alliance SL is just what every modern home needs. It comes with a proven technology that not only delivers hot water on demand. It also ensures you get the top-rated energy consumption savings for your family.

At the core of the Alliance SL is an advanced heat exchanger coil. The component can raise the water temperature fast, so you can start enjoying a hot shower within minutes.

The high-capacity coil ensures more energy goes to the tank to heat the water. It also brings faster recovery times, allowing you to enjoy more hot water.

Surrounding the interior of the Burnham Alliance SL tank is Hydrastone. The design prevents the adhesion of water molecules on the inner surface of the tank. So that you know, preventing the adhesion of contaminants on the surface can lead to corrosion suppression.

The tank also features a thick insulation material. It prevents heat from escaping from the tank. There is still heat loss but not as significant as other brands.

Aiding the insulation material in retaining heat is the water-tight seals. You will feel more confident about getting 30 percent greater energy efficiency than a standard water heater.

Most Burnham indirect water heater reviews are positive. It says a lot about the quality of the product. However, some customers complained about the quality of the brand’s customer service.

Personally, I think some people will find the design of the Alliance SL a deal-breaker. There are no significant changes from the product’s previous versions.

Still, the Burnham Alliance SL remains a good indirect heater. Its design may not be the best, but it can handle the hot water needs of the modern family.
What We Like
  • Features a high-capacity, advanced heating coil
  • The system comes with a corrosion-resistant lining made of Hydrastone
  • 30 percent more efficient than conventional direct water heaters
  • Features a high-density insulation material for improved heat retention
What We Don’t Like
  • Its design is the same as the previous versions
  • Some issues with customer support

2. HTP SSU45 SuperStor Water Tank

If you consider the different SuperStor indirect water heater reviews, you will know that the HTP SSU45 SuperStor Ultra means business. It has the ideal capacity for a medium-sized family. The technology is also advanced enough to ensure greater energy efficiency.

With a 45-gallon capacity, the SuperStor Ultra can provide hot water for everyone in a family of four. You can have a hot shower while other members of your household enjoy their hot coffee.

The efficient design of the SuperStor Ultra not only gives you hot water when you need it. It also allows you to enjoy greater savings you can use for a family holiday.

One of the things that amaze me about the SuperStor Ultra is its low heat loss rating. Most of the indirect water heaters on the market lose as much as 1-degree Fahrenheit per hour.

The SuperStor Ultra only loses half of that. The heat retention capability of this indirect water heater assures you of a consistent supply of hot water.

The thick insulating layer of the tank also helps improve the heat retention capability of the SuperStor Ultra.

Heat Transfer Products (HTP) constructed the SuperStor Ultra from premium quality 316L stainless steel. We all know how effective stainless steel is in terms of corrosion prevention. You will never have issues with rust sediments collecting at the bottom of the tank.

The downside to the SuperStor Ultra is its port threads. The threads are a bit shallow. It would help if you were careful when connecting your water pipe to the ports. If not, there is a tendency for leaks to occur.

I suggest hiring a professional plumber to install the system if you are not confident about installing it yourself.

Any family who wants an energy-efficient home can depend on the indirect water heating performance of the HTP SuperStor Ultra.

What We Like
  • Energy-efficient design
  • Recommended for small to medium-sized families with its 45-gallon capacity
  • The heat losses are almost negligible, only half than 1-degree Fahrenheit per hour
  • Features stainless steel tank construction for corrosion-resistance
  • Comes with thick insulation for better heat retention capability
What We Don’t Like
  • Shallow threads on the tank’s stainless ports
  • It has a tendency to leak if not installed correctly

3. Triangle Tube SMART80 Water Heater

The SMART80 Phase III is one of Triangle Tube’s best-selling indirect water heaters. This product is perfect for homes that want to replace their existing boiler with a more energy-efficient product.

It has unique tank-in-tank technology. In detail, the outer tank serves as the boiler for the system that heats the rest of the house. It can provide up to 300,000 BTU per hour.

The inner tank’s wall serves as the system’s heat exchanger, giving the system exceptional heat transfer capabilities.

Triangle Tube also designed its system to have self-descaling and self-cleaning capabilities. Maintaining the system and keeping it in tip-top shape will be the least of your concerns.

You also will not worry about massive heat losses regardless of water conditions. The thick insulation of the tank takes care of that.

The system has a continuous flow rate of 400 gallons and a first-hour recovery rate of 460 gallons. It can deliver 12.5 gallons of hot water per minute. Large families will never complain of not having sufficient hot water supply.

Many Triangle Tube indirect water heater reviews speak highly of the SMART80 Phase III. However, there are a few issues that potential buyers need to be aware of.

It requires a minimum floor area of 30 by 30 inches, including a 2-inch allowance on all sides. This indirect water heater seems rather bulky, with a weight of 271 pounds. Note that installing the indirect heater by yourself is dangerous.

Once installed, you can start enjoying hot water on demand. You will also reap the benefits of having an energy-efficient system working for your family. These are what this heater offers. I cannot see why you should not consider getting this unit for your home.
What We Like
  • Features a revolutionary tank-in-tank technology
  • Doubles as a boiler and a water heater
  • It has a good first-hour recovery rate of 460 gallons
  • High continuous flow rate of 400 gallons (equals 12.5 gallons per minute)
  • The system comes with 2-inch thick foam insulation for better heat retention
  • Features a self-descaling and self-cleaning heat exchanger
What We Don’t Like
  • Requires professional installation
  • Heavy and bulky compared to other products

4. Westinghouse WER080C2X045

The Westinghouse WER080C2X045 is an 80 gallon indirect water heater that large households should always consider buying. It is efficient and can provide enough hot water for a platoon.

This 69-inch tall indirect water heater delivers up to 98 percent thermal efficiency. It has a first-hour delivery rating of 84 gallons and a recovery rate of 20 gallons per hour. The system only allows heat losses of up to 0.57 degrees Fahrenheit per hour.

The combination of its capacity and energy efficiency delivers hot water to everyone in a large house. The energy efficiency of the indirect water heater also translates to more savings. You can use the money you save for other activities your family will enjoy.

What many people find striking about this unit is its lightweight characteristic. Most products of this size and capacity often weigh at least 200 pounds. The one from Westinghouse only weighs 151 pounds.

The use of 316L stainless steel in the best indirect water heater construction has a lot to do with its lightweight and corrosion-resistant characteristics.

It might alarm you that some customers complain about the heat exchanger’s durability. If the issues about durability are real, they can be expensive junk. What is comforting to learn is that more customers are happy with the Westinghouse stainless steel heater’s performance.

Despite these issues, the Westinghouse WER080C2X045 remains popular among many households. Its large-capacity tank and excellent thermal efficiency are enough to mitigate any concerns about heat exchanger durability issues.
What We Like
  • High level of thermal efficiency
  • Negligible heat losses through the tank wall
  • Features corrosion-resistant stainless-steel tank
  • Elegant and ultra-modern indirect water heater design
  • Lighter than other indirect water heaters of the same size and capacity
What We Don’t Like
  • Some customer complaints about the heat exchanger’s durability

5. American Standard CE-12-AS Water Heater

The top-tier indirect hot water heater should not always be big and bulky. Neither should it always be a permanent fixture in your home. If you are one of those users who value space-saving features, the American Standard CE-12-AS is for you.

It is an indirect water heater that many people use in their motorhomes. It is small, yet provides enough hot water for two people. Do remember that its capacity is only 12 gallons. I do not recommend this for households with a high demand for hot water.

American Standard designed the CE-12-AS with superior durability in mind. The device features a steel tank construction that will help it serve you and your partner for many years.

You do not even need a boiler to enjoy indirect hot water. You can plug it into a 120-volt outlet, and you are ready to enjoy hot water within minutes. Its heat exchanger does not always draw that much electric power. It only requires 1500 watts. Other systems can draw as much as 4800 watts.

The energy efficiency of this product is also commendable. It can generate at least 71,600 BTUs per hour. Set the thermostat to the highest setting, and you get to enjoy 512,000 BTUs per hour.

Losing heat from the system is also not an issue. This one provides enough insulation to limit heat losses to less than 1 degree Fahrenheit.

Aside from the fact that this heater is only for a two-person household, there are also concerns about the product getting damaged during shipping. I think this is the downside of a small unit.

Buy the American Standard CE-12-AS if you live alone or with your partner. It is also great for those who want to augment the water heating systems of their motorhome.

What We Like
  • Space-saving design for small households and motorhomes
  • Features a heavy-gauge steel tank construction for durability
  • Easy to install, operate, and maintain
  • The system does not require an existing boiler as a heat source
  • High thermal efficiency for more energy savings
What We Don’t Like
  • Only good for one or two people
  • A few packaging and shipping concerns

6. Crown MS2-50 Water Heater

The MS2-50 is one of five variants of Crown’s Mega Stor series of indirect water heaters. This product has a nominal potable water capacity of 53 gallons which is enough for a medium to a large household. It can also be an option for small houses with a heavy demand for hot water.

It has a first-hour rating of 236 gallons per hour and a continuous draw rating of 193 gallons per hour. The figures underscore its capability of supplying your home with sufficient hot water.

The built-in Honeywell aquastat also allows for more efficient control of the tank’s temperature and pressure settings.

I like the design of this heater. It looks solid. The coated steel jacket gives you a sense of security, knowing the system is resistant to abrasions and cracks. If you look at the feet, you will notice an adjustable height mechanism. It helps ensure better stability for the indirect water heater system.

While I appreciate the energy efficiency of the MS2-50, I wish Crown could improve its insulation. The rate of heat loss of this unit is higher than most indirect water heaters on the market.

It has a standby heat loss of 0.9 degrees Fahrenheit per hour. Some products have a heat loss rating of about half a degree.

Installing the unit should be easy if you have basic plumbing knowledge and skills. Otherwise, I suggest getting the services of a professional plumber to install the system in your house.

Other than these concerns, the Crown MS2-50 Mega Stor is a good indirect water heater. It provides enough hot water for medium to large-sized households. It is also efficient enough to let you enjoy the savings you get from using this device.
What We Like
  • Recommended for medium-sized households with average hot water demands
  • Good energy efficiency performance ratings
  • Features an adjustable aquastat for optimum boiler temperature control
  • It comes with a rugged design for crack and abrasion resistance
  • Features adjustable feet for maximum stability
What We Don’t Like
  • Higher rate of heat loss than other brands
  • Requires basic plumbing skills for the installation process

7. Triangle Tube SMART40 Water Heater

Not all indirect water heaters are compatible with existing boilers. Not all homes also have an existing boiler. Either situation is a good indication for the Triangle Tube SMART40 Phase III.

It is the scaled-down version of the SMART80 system. You get all the remarkable performance of the bigger unit in a smaller package.

This unit, utilizing a unique tank-in-tank technology, is perfect for houses that want a more efficient heating system that gives them a steady supply of hot water. It is also a good option for replacing an existing boiler system with a more energy-efficient one.

It has a first-hour recovery rating of 180 gallons and a peak flow of 5 gallons per minute. Its recovery rate is three times faster than conventional electric or gas water heaters.

The boiler system can provide enough warmth for a small house with its 112,000 BTU per hour output.

The thick insulation also helps improve the system’s overall energy efficiency. The current heat loss rating is about 0.5 degrees Fahrenheit, although the real-world application may indicate a higher value.

Regardless, the heater from Triangle is efficient enough to let you enjoy continuous hot showers on demand. The system also offers hassle-free maintenance, thanks to its self-descaling and self-cleaning capabilities.

The indirect hot water heater reviews for the SMART40 Phase III are mostly positive. The only real issue I see from these customer reviews is the tendency of the system to leak. Leaks are often the result of poor connections.

Save yourself from these leaky issues by having a professional install it for you. It may increase the overall cost of the system, but it is worth it.

With its excellent hot water recovery and high energy efficiency ratings, you will be glad to bring the Triangle Tube SMART40 home.

What We Like
  • Ideal for households that do not have an existing boiler
  • Excellent ratings for superior energy efficiency
  • Extra-thick insulation for optimum heat retention
  • The system has a good first-hour recovery rate
  • Easy to operate, clean, and maintain
What We Don’t Like
  • It tends to leak if not properly installed
  • A bit expensive if it includes the installation fee

8. Amtrol BoilerMate WH-41Z

Amtrol introduced the world’s first indirect-fired water heater system in 1980. The brand continues to design and create water heaters that produce sufficient hot water with minimal fuel expenditure. The BoilerMate WH-41Z is one of these products.

It is unique from other indirect water heater systems because of the placement of its heat exchanger. While most products have this component enter through the tank’s sidewall, the BoilerMate has its heat exchanger mounted on top. The design allows for a more efficient heat transfer. You get hot water faster.

Amtrol also uses a mechanical aquastat instead of a digital controller. You get better control of the pressure and temperature settings of the WH-41Z. The aquastat lets you crank up the rate of water heating, so you get to enjoy hot showers a lot faster.

I like the bimodal HDPE construction of the BoilerMate tank, which is more corrosion-resistant than most materials on the market. The steel base is also solid and secure. It will never tip over once installed.

The majority of BoilerMate indirect-fired water heater reviews point to one flaw. It seems to be less durable than its published service life. Some customers say that their BoilerMate gave up on them after only a year of use.

However, some clients report that the BoilerMater has been with them for many years. Unfortunately, it is difficult to pinpoint the exact cause of the durability issues.

There are also concerns about leaks. One can always avoid such issues by installing the system correctly.

Durability issues aside, the Amtrol BoilerMate remains a good choice for small to medium-sized households. The fact that Amtrol pioneered indirect-fired water heater technology is enough to give you a sense of security about the overall performance of the BoilerMate.

What We Like
  • Features a top-mounted heat exchanger for more efficient heat transfer
  • It comes with a mechanical aquastat for improved control of the settings
  • It has good resistance against corrosion
  • Ideal for households with an existing boiler system
  • Rugged steel base for better stability
What We Don’t Like
  • Its durability is in question
  • There might be leaks in water heater connections if not installed correctly

9. O. Smith ENS-50 Water Heater

A.O. Smith is a reputable brand of residential water heaters. The brand offers different water heating devices, including those that run on gas, electricity, and hybrid technology. One of the brand’s most successful electric indirect water heaters is the ENS-50 ProMax.

It has enough tank capacity to provide a family of five a continuous supply of hot water. If your household does not use that much hot water, this unit should also fit right into a large family of 10.

I find the anti-corrosion technologies featured in the ENS-50 ProMax simply amazing. There is a CoreGard anode rod that attracts charged particles from the tank wall. These particles adhere to the rod and prevent corrosion on the wall.

There is also a DynaClean diffuser dip tube that works in tandem with the CoreGard. The DynaClean reduces the formation and accumulation of sediments and lime. Preventing lime buildup helps improve the overall output of the ProMax.

Covering the steel tank is a Permaglas coating. It aids in the prevention of corrosion. It also helps that the drain valve features tamper-resistant brass. All of these technologies work together to provide you with a more energy-efficient water heating system.

Speaking of energy efficiency, ProMax meets all the standards of the National Appliance Energy Conservation Act.

Like other indirect water heaters, the product from A.O.Smith is still prone to leaks if not connected properly. A professional plumber can help you make a watertight connection.

There are also a few complaints about the water heater’s durability. However, most consumers say it is one of the most durable indirect water heaters on the market.

The A.O. Smith ENS-50 ProMax is one of the most dependable indirect hot water storage tanks for residential applications. Its anti-corrosion technologies are excellent, and its water-heating capability is unmatched.

What We Like
  • Large capacity tank for use in medium-sized homes
  • Features multiple anti-corrosion technologies for maximum tank life
  • Energy-efficient design
  • It comes with a tamper-resistant drain valve
  • Meets NAECA standards
What We Don’t Like
  • May leak if poorly installed
  • A few issues about the product’s durability

Outdated Products

Rheem MR50245 Marathon Tall Electric Water Heater (Outdated)

The Marathon is Rheem’s offering to the modern household that requires a reliable water heating system. It is a system that has a good energy efficiency rating. You can spend the savings you get from using this system on other things the whole family can enjoy.

Most indirect water heaters come with steel construction. The Marathon does not. In fact, this indirect hot water tank comes with fiberglass construction. It gives the system lightweight and corrosion-resistant characteristics. The fiberglass framework also allows this unit to be as strong as steel.

I admire the insulation of the Marathon. You can fire it up today, and you will still have hot water the next day with the system on standby. The system has a heat loss rating of about 0.5 degrees Fahrenheit, making it par with leading indirect water heaters.

There is also no danger of frying the system. It has enough protection to prevent it from running without water.

The watertight design of the Marathon improves its energy efficiency. While some systems have an energy efficiency rating of 98 to 99 percent, Marathon’s 90 to 94 percent is still higher than most.

There is no fretting about your electric consumption, either. Its energy efficiency takes care of that.

My only concern about the Marathon is its low hot water recovery rate. Other products can recover as much as 5 gallons of hot water per minute. The Marathon can only recover 20 gallons per hour.

Moreover, the thermostat and check valves are prone to fail. The good news is that the replacement parts are standard. You can easily swap a part for a new one.

The Rheem Marathon is a reliable indirect water heater. It is energy-efficient and can deliver the right amounts of hot water for your family.

What We Like
  • The system has a high energy efficiency rating for maximum energy savings
  • Near-negligible heat loss for long-lasting hot water
  • Comes with safety features against dry-firing
  • Corrosion and rust-resistant polybutene water tank
  • Features lightweight fiberglass tank construction
What We Don’t Like
  • A few water heater parts are prone to fail
  • Lower hot water recovery rate than other brands

What Is An Indirect Water Heater/ Who Is This For


Indirect water heaters are a low-cost and energy-efficient system that delivers hot water as needed. The system relies on an existing boiler, furnace, or any other whole-house heating system to heat the water. These devices have a heat exchanger coil that uses the energy from a boiler or a furnace to heat the water.

Some of these devices have a tank that serves as storage for hot water. The capacity is sufficient to supply the needs of everyone in the family.

An indirect water heater can work with any modern household heating system. You can enjoy hot water even if you have a gas-fueled boiler or an electric version. The product also works with heating systems that use propane, oil, and solar power.

Indirect water heaters are ideal for both large and small households. These technologies are suitable for anyone who wants a more cost-effective way of heating water.

How Do Indirect Water Heaters Work

Families living in cold regions often have a whole-house heating system. Two of the most common types of household heaters are boilers and furnaces.

These systems generate heat to warm up the place. You can also use this thermal energy to heat your water. It is the basic principle behind the design of an indirect water heater.

The only real question is how to get the boiler’s thermal energy to raise the water temperature.

The traditional design of this kind of energy-efficient water heater system involves a boiler with indirect water heater. The design calls for the indirect water heater to establish a connection with the boiler system. A pipe terminates in a series of coils inside the indirect water heater device.

The boiler’s thermal energy passes through the heat exchanger coils to raise the tank water temperature. When you open your faucet or your shower, you get hot water from the tank.

A water pipe connects to the indirect water heater through the cold-water inlet located at the water heater tank’s top. Using hot water from the tank automatically refills the water heater with ordinary water.

The heat exchanger coils continue transferring their heat into the water to raise its temperature.

There are also indirect water heaters that do not use a tank. These systems have water pipes that terminate in a heat exchanger in the boiler or a furnace.

As water passes through these pipes and the heat exchanger coils, the water picks up energy or heat.

What Are The Different Types Of Indirect Water Heaters


Most people categorize indirect water heaters according to whether they have a tank or not.

Indirect Water Heaters with Integrated Tanks

This type of indirect water heater is widespread among large households. The system consists of a water tank that can hold a predetermined volume of water.

Inside the tank is a coil that draws heat from an external source. The external source that these indirect water heaters use is often a boiler. The hot water in the heat exchanger coils slowly raises the water temperature in the tank.

One advantage of this indirect water heater is that you have a steady supply of hot water. As you use up the hot water, cold water goes into the tank so that the heat exchanger will also heat the water.

However, the supply depends on the capacity of the tank. If the hot water usage exceeds the indirect water heater’s capacity, it is still possible that the household will not have enough supply.

Another disadvantage of this type of indirect water heater is the amount of space that it requires. Remember, the design of this system is essentially that of a water tank. The indirect water heater may not be ideal for homes with inadequate space. It is also worth remembering that tanks require regular cleaning and flushing.

Tankless Coil Systems

This type of indirect water heater does not have a tank (tankless water heaters). That is why people refer to them as “‘tankless.” You only have the heat exchanger coil that connects to your water pipe.

The heat from your domestic heating system warms up the water present in the heat exchanger coils. The water then circulates to the different water fixtures in the house.

The advantage of tankless water heaters is that they do not require too much space. You also get an unlimited supply of hot water. No wonder people also like to call them an “on-demand” system.

However, a tankless coil indirect water heater system is not ideal for large households.

If there are too many people using hot water simultaneously, there might not be enough water getting heated through the coils or with a tankless water heater.

Pros and Cons Of Indirect Water Heater

Indirect water heaters offer several advantages that modern families will find appealing.

Improves Energy Efficiency in the Home

One of the most superior advantages of an indirect water heater is energy efficiency. Indirect water heaters work best with an existing boiler system or a furnace heating system.

You get to heat your house while also gaining access to a continuous supply of hot water. The design of the system allows you to utilize the heat from your boiler.

Less Maintenance

Indirect water heaters are also easier to maintain than conventional water heaters. There are fewer mechanical parts to worry about. These systems do not have an actual heating element in their tank.

Greater Savings in the Long-term

Energy-efficient systems always offer considerable savings in the long term. An indirect water heater is no different. Not only do you save on heating your home.

You also save on heating your water. You will be using the energy coming from your boiler. Doing so eliminates the need for a separate system for heating your water.

More Durable

Indirect water systems also last longer than conventional direct water heaters. These energy-efficient systems do not undergo rapid expansion and contraction due to abrupt changes in water temperature. It saves the metal tank from fatigue.

Requires Less Space

In general, indirect water heaters are smaller than direct water heaters. The tank is smaller than a traditional water heater tank.

It allows you to save space while enjoying the benefits of having an on-demand hot water system in your house.

There are a few disadvantages of indirect water heaters.

Expensive to Set Up

While this technology is cost-effective, you will not realize the savings until after a few years. The purchase cost of the unit is higher than a direct water heater. There is also the cost of the installation process that you will have to think about. All of these expenses are part of the initial setup of the system.

Boiler Compatibility Issues

Not all indirect water heaters are compatible with boiler systems. Outdated boilers may not have the necessary components to connect to a modern indirect water heater.

May Tax Older Boilers

Most people use their boilers only during the cold months. They no longer need their boilers during the warm summer months. However, they may still require hot water. The boiler will have to work the whole year, increasing wear on the boiler system.

Buying Guide


I have listed here some of the more important considerations when buying an indirect water heater.

Type of Indirect Water Heater

If you already have a boiler in your home, I recommend getting an indirect water heater with an integrated tank. However, you must check your boiler to see if you can fit it with a modern indirect water heater.

You can also check the indirect water heater you want to buy if it is compatible with your boiler.

Ensure that the water heating systems work with the type of energy source you have in your house.

Will you be connecting it to a boiler? Will you plug it into an electrical outlet? Does it work only with gas-fired boilers? Does it require gas heating elements in the tank? These are just some of the questions you need to think about.

If you have a furnace, then it would be best to get a tankless indirect water heater.

Energy Efficiency and Other Technical Specifications

Consider the energy efficiency rating of the product. In general, a higher rating translates to greater energy efficiency.

You may also want to check the other technical specifications of the product you want to buy. For example, you can look at its Recovery Rate (RR), First Hour Rate (FHR), and British Thermal Unit (BTU) rating.

The FHR is important because it gives you an idea about the amount of hot water the system can provide in the first hour. You can check this by multiplying the system’s capacity by 70 percent. You can then add the RR.

It is best to get an indirect water heater with a high FHR. It should be as close as possible to the maximum amount of hot water that you need at any given time.


A 40 gallon indirect water heater is sufficient for households of three to four people. If there are only two people in the house, then you might want to get an indirect water heater with a smaller capacity. The opposite is true for large households.

Check your average daily hot water consumption. It should be less than the capacity of the tank.

For example, if you consume 35 gallons of hot water per day, then a 40-gallon tank is enough. The difference should provide enough allowance to account for any ‘emergency.’

Customer Reviews

Customers can share with you their experiences with a product. These experiences can provide you with insight as to how the product works in the real world.

You may also get to learn a few advantages and disadvantages of the product. For example, if you want an IBC brand, you might want to focus on IBC indirect water heater reviews.

Physical Dimensions

Indirect water heaters are indeed smaller than direct water heaters. However, you will still need to consider the physical dimensions of the product you wish to buy.

It is also essential to give an allowance for the fixtures to connect the system to your boiler.

A good way to do this is by looking at the area where you intend to place the indirect water heater. Measure the floor space and the vertical clearance of this area.

You should be able to get an idea of the size of the indirect water heater you will buy.


For buyers of an indirect water heater, price is always going to be an issue. Many of these systems cost more than conventional direct water heaters.

On average, indirect water heaters can cost you between $800 and $1,500.

Moreover, consider the cost of its installation process. Hiring a professional plumber can increase the installation cost by several hundred dollars.

Frequently Asked Questions (FAQs)

Where can I place an indirect water heater?

The most suitable location for indirect stone-lined hot water heaters is adjacent or as close as possible to the boiler. After all, even a high-efficiency Weil Mclain indirect water heater cannot produce its heat but relies solely on a boiler system. The nearer the indirect water heater is to the boiler, the lower the heat losses.

Homeowners must also place the appliance in an area that minimizes water-related damage to adjacent gadgets and structures. Leaks can occur in water connections or the tank, spilling into an electric device or a living space underneath the Techtanium indirect water heater or any other brand.

If no such space is available, a drain pan is necessary. In my case, I place it underneath my Superstore hot water storage tank and connect it to the drain. This setup is necessary to avoid costly repairs.

Some brands require a two-foot clearance around the indirect water heater to facilitate access to various fittings. Homeowners must also ensure ample protection against rain, snow, and water sprays for electronic components.

An indirect electric water heater should be central to all point-of-use fixtures. For example, the kitchen faucet must be as close to the indirect water heater as the bathroom faucet.

How long does it take for an indirect water heater to heat up?

An indirect water heater should take slightly longer to heat the water than a conventional water heater. We must recognize that a small indirect water heater relies on the hot liquid coming from the boiler.

For example, a gas-powered water heater can heat the water in half an hour, while an electric version requires 60 to 80 minutes. Hence, it would be safe to assume that a 50 gallon indirect water heater will take a little longer than 30 minutes to raise the water temperature to the ideal levels.

An indirect water heater’s heating performance matters because running out of hot water is inconvenient, especially if one is showering. Hence, you might want to check the indirect water heater’s specifications before buying.

An indirect vs direct water heater: what is the difference?

The only difference between an indirect and direct water heater is the heat source.

Direct water heaters have integrated heating systems within the storage tank. Gas-powered units have a burner at the bottom to heat the water, while electric versions have electrically connected heating elements.

Meanwhile, an indirect water heater (i.e., a Peerless indirect water heater) features a coil-type heat exchanger. This twisty pipe accommodates hot water from the boiler. Heat transfers to the water in the storage tank as hot water moves through the coil. It is a similar mechanism you can expect from a Bosch or any other indirect water heater brand.

According to the US Department of Energy, indirect water heaters are the “least expensive” systems for producing hot water. This attribute also differentiates them from direct water heaters.

Are more expensive water heaters better?

We have this inclination that more expensive items are better than lower-priced things. This belief extends to water heaters, whether direct or indirect.

Some higher-priced water heaters are better than average because they feature proprietary technologies. For instance, Heat-Flo indirect water heater reviews cite stainless steel construction, two-inch insulation, and smooth-wall coils as the brand’s principal selling points, which buyers may not find in other indirect water heaters.

It is the same story with Lochinvar, with some users commenting it is a world-class company with exceptional products and unparalleled customer support.

However, we must also recognize that some brands offer high-performance indirect water heaters at friendly prices. A good example is Rheem’s most durable indirect water heater – the STID50.

Why are indirect water heaters expensive?

Many first-time buyers ask “why are indirect water heaters so expensive?” You might be surprised that the price difference between indirect and direct water heaters is not that far off.

For example, a 40-gallon direct water heater can cost $300 to $1,600. A similarly sized indirect water heater can cost $350 to $1,600. Hence, indirect water heaters are not really “expensive” compared to direct water heaters.

However, we must recognize that top-tier brands have proprietary technologies that can jack their prices higher than the competition. For example, Viessmann uses a revolutionary Vitocell tank to contain and heat the water. This system allows its indirect water heaters to guarantee maximum efficiency and performance.

What are the most trusted indirect water heater brands?

Burnham is one of the most dependable brands of indirect water heaters on the market. The company’s products are popular because of the high-tech features that these devices have.

You might also want to check out Triangle Tube and HTP. These two brands provide impressive water heaters that are not only efficient but also feature robust construction.

You can expect the system to last you several decades with the proper care.

If installation space is an issue, you might want to check out the Buderus indirect water heater. The brand is famous for its space-saving design. Other popular brands to look for include Westinghouse and American Standard.

Rheem, A.O. Smith, Crown, and Amtrol are also popular choices. These brands provide models with different features. I recommend studying the unique characteristics of each one. Make sure to pick only the indirect water heater that fits the needs of your family.

How long does an indirect water heater last?

Indirect water heaters can last up to 20 years. Some brands can last up to 25 years and maybe even more. The reason for this is the design of these products.

They do not undergo rapid heating and cooling, unlike conventional water heaters.

The water inside the tank of an indirect water heater does not heat up very fast. The addition of cold water from the top of the tank also does not shock the system. The more gradual change in water temperature prevents the metal from expanding and contracting at a rapid rate.

An indirect water heater tank also has a few mechanical components that can deteriorate over time. Many of these products also have a more robust construction compared to traditional water heaters.

While indirect water heaters are durable, they also require regular maintenance. You can ensure the integrity of your system if you perform regular flushing of the tank.

How big of an indirect water heater do I need?

The size of the indirect water heater you need depends on your hot water consumption. If you consume 40 gallons of hot water every day, you should get a 50-gallon indirect water heater.

It is better to give yourself some allowance for those ‘just-in-case’ situations. You will never know.

It would be best if you also took note of the peak demands of your household. There are certain times of the day when you consume more hot water than at other times.

Mornings are always hard for water heaters because of the increased demand for hot water.

You might also want to check the average hot water consumption of each member of your household.

Some people may already be content with only a few gallons of hot water during a shower. Others may require more.

A 40-gallon unit is often enough for an average household of three to four members.

How much does it cost to install an indirect water heater?

Installing an indirect water heater can be expensive. You can spend $800 on a good indirect water heater. If you want a more robust system, you may need to shell out $1,500 or more.

Knowledge of basic plumbing can help lower the cost of installing the system in your home. Otherwise, you will have to hire a professional plumber to install the system. Professional plumbers can charge you between $250 and $550.

Your existing boiler system can also be a determinative factor in the cost of installing an indirect water heater. You will not spend that much if it is already compatible with your water heater.

If not, you will also need to make some changes to your boiler to accommodate the indirect water heater. Changes in your boiler entail additional expenses.

Connecting the system to your existing water supply also requires the correct fittings to ensure a leak-proof connection.

How to care for and clean?

Getting the most out of your indirect water heater requires observing proper care and maintenance. The following tips should help.

  • Do not underestimate the value of an owner’s manual. It can provide you with important information about the proper care and maintenance of your unit.
  • Inspect your indirect water heater every month. Check for signs of leaks or damage.
  •  Hire a professional service technician to perform a comprehensive assessment of the unit once a year. He needs to check the thermostat and other important components of the indirect water heater.

If your unit relies on electric power, make sure to turn the unit off whenever there is no water going to the indirect water heater.

  •  Drain the water in the tank once a month. Open the water inlet and allow water to flow into the tank to flush the water heater tank’s insides.
  • Check the water coming out from the system’s drain valve. You can close the water inlet and the drain valve once the water already turns clear.
  •  Check the relief valve on top of the tank. Take note of lime encrustation.
  •  Check the correct positioning of the pressure-temperature relief valve. The relief valve has a lever at the top. Lift the lever several times to ensure proper valve placement. Also, check for signs of a leak.
  • Check the seals at least once every six months. These parts of the indirect water heater can deteriorate over time because of the heat in the tank.

Where to buy it?

Amazon remains the largest marketplace to get your indirect water heater. The top-rated part about shopping in this online commerce platform is that it comes with customer reviews.

Even if you cannot examine the product in person, you can make near-accurate assumptions about the product. You can read the customer experiences to get an idea of what you are buying.

You can also buy an indirect water heater straight from the official website of the manufacturer. One good thing about this approach is that you can be sure about the quality of the product you are getting. You may not be able to enjoy the freebies that retailers offer, however.

Other popular options include eBay, Home Depot, and Lowes, among others. One issue with these online commerce platforms is that they often do not carry an extensive selection of products to choose from. That is why you should check Amazon first.


Choosing the best indirect water heater requires an understanding of the basic design of the system. Efficiency is the name of the game.

That is why it is vital to choose an indirect water heater that has energy-efficient features. Examining the technical specifications of the product is essential in determining its energy consumption efficiency.

Knowing the space requirements for the system and the different materials for its installation can also help narrow your choices.

Other considerations matter, too. If this still does not help, the ten indirect water heaters I reviewed and shared with you should set you on the right foot.

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