Best Tankless Water Heater Reviews of 2018

Are you tired of paying money to constantly heat up water in a tank, just to run out of it every time Aunt Patricia is over for the holidays? Well, with a tankless water heater, not only will you benefit thanks to the endless supply of hot water, but you’ll also get to save precious space in your home from not having to deal with a bulky tank.

This is all thanks to the tankless water heaters design – which allows it to heat water “on-demand” as it passes through the unit’s heat exchanger. Compared to constantly heating water in a tank, this is a much more efficient way of doing things (around 25 – 35% more efficient to be exact).

This increase in efficiency will not only save you money on your utility bill, but will also help you do your part in taking care of the environment. However, in order to buy the best tankless water heater for your home – it’s important you know what to look out for; as there are a wide variety of different types and sizes you can choose from.


Top 6 Tankless Water Heaters

While a tankless water heater can used virtually anywhere (as long as the house meets the proper requirements), they do tend to work better in certain situations than others. For instance, it’s much easier to heat water to a higher degree when the inlet water temperature is already fairly high.

This doesn’t mean that a tankless water heater won’t work well in colder regions – but you’ll likely have to get a natural gas or propane model; as an electric unit probably won’t be sufficient enough to heat the colder water coming into your home. On the other hand, if you happen to live somewhere that’s fairly warm year-round, an electric tankless water heater will do just fine.

Unfortunately, this is only scratching the surface of information you need to know when it comes to buying the best tankless water heater for your home. To make your life simple, below are some of the basic questions that you’ll first need to answer.

  • How cold does your inlet water temperature get in the winter?
  • What’s the flow rate in GPM (gallon per minute) you need to supply your hot water demands?
  • Do you want a natural gas, propane or electric model?
  • Do you want to install your unit indoors or outdoors?

If you’re unsure of the answer to these questions, then we recommend you skip our tankless water heater reviews for now and read our buyers guide further down the page. However, if you’ve already done your research on the size and type of tankless water heater you want to buy, but are just unsure which brand or model to go with, then don’t worry – we’ll take it from here.

Takagi T-KJr2-IN-NG Indoor Tankless Water Heater

best tankless water heater - Takagi T-KJr2-IN-NG

Even though the Takagi T-KJr2 is the smallest model that Takagi offers, it still can do everything a 40 gallon tank water heater can do and more. This unit is also slightly more powerful than your typical electric tankless water heater, making it a better option for people who live up north – as it’s more likely to keep up with your hot water demands.


With a BTU input of 19,500 to 140,000 BTU per hour, the Takagi T-KJr2 is capable of a maximum flow rate of 6.6 GPM at a 35°F temperature rise, and 3.3 GPM at a 70°F temperature rise. This kind of flow rate is enough to provide hot water to a small home with 1 to 2 bathrooms (depending where you live), or it could even be used to support a hydronic baseboard or radiant floor heating system.

As far as efficiency goes, the T-KJr2 has an energy factor of 0.82, which essentially means it has an efficiency rating of 82%. This type of efficiency rating is normal for a non-condensing, or “mid-efficiency” tankless water heater. Non-condensing meaning that it only uses one heat exchanger to heat the water passing through the heater.

This water heater is also a Low NOx model, meaning that it reduces NOx (nitrogen oxide) emissions. This not only helps you save the environment, but also allows it to comply with the low NOx emission standards enforced in states such as California and Texas.

Main Features

  • Low NOx Emission: It’s important to take care of the environment and owning a Low NOx tankless water heater helps you do your part.
  • Safety Features: Comes with built-in freeze protection, flame sensor, manual reset hi-limit, and an overheat-cutoff fuse.
  • Inlet & Outlet Thermistors: The thermistors help you to easily monitor the temperature at all times. Many people even opt in for buying the TK-REO2 remote control.

Installation Tips

If you plan on buying the indoor model of the Takagi T-KJr2, it’s important you order the TK-TV10 conversion kit if you’re wanting to switch your unit from a power vent to a direct vent system. By doing so, your water heater will be able to bring in combustible air from outside your home, thereby giving you the ability to store your tankless water heater in a much smaller room – such as a closet or attic.

Whenever installing a non-condensing tankless model indoors, category III stainless steel venting is required due to the heat of the exhaust gases leaving your home. If you live in an area that experiences freezing temperatures below 36 °F, you may also want to consider installing a backflow preventer as well.

Rheem RTG-95XLN Outdoor NG Tankless Water Heater

tankless water heater reviews - Rheem RTG-95XLN

If you’re interested in getting a natural gas tankless water heater, but also want to install your unit outdoors, then the Rheem RTG-95XLN may just be for you. While we decided to review the most powerful model from their Professional ™ line, there are many other sized models you can buy as well.


The Rheem RTG-95XLN has an impressive BTU input range of 11,000 to 199,000 BTU per hour. With that kind of BTU input, this unit is capable of heating up to 9.5 GPM at a 35°F temperature rise, and 7.4 GPM at a 45°F temperature rise.

Rheem has even performed an industry first with their on demand water heaters by having a 0.26 GPM minimum flow rate, and a 0.40 GPM minimum activation flow rate. This ensures that you have hot water even when barely turning on the faucet at all.

In addition, this unit has an energy factor of 0.82 thanks to the stainless steel condensing heat exchanger. Intelligent electronic controls are even included to increase efficiency and safety.

Main Features

  • Digital remote control – This is perfect for cold or rainy days when going outside to change the temperature or shut it off is too much of a hassle.
  • Hot start programming – This feature helps to minimize fluctuation in water temperature during periods of time where water is being frequently turned on and off. This is commonly referred to as “cold water sandwich”.
  • Self-diagnostic system – The self-diagnostic system makes performing installation and service is fairly simple process for anyone that’s mechanically inclined.
  • Digital display – Allows you to easily see the temperature setting and maintenance codes.
  • EZ-Link cable – If you’re interested in installing a secondary unit, all you have to do is buy an EZ-Link cable and that’ll allow you to connect two units that will then operate as one.

Installation Tips

Because the Rheem RTG-95XLN is installed outdoors, you get the added benefit of saving space in your home – as well as money on venting materials. Just make sure to install your tankless water heater in a safe location where the exhaust gas won’t be blown into any windows, doors, etc.

You may also want to consider getting an indoor model if the temperature in your area commonly drops below freezing. While the RTG-95XLN may have built-in freeze protection to -30°F, it’s still recommended that you take certain precautions in case something goes wrong (such as your power being shut off).

Ecosmart ECO 27 Electric Tankless Water Heater

Ecosmart ECO 27 on-demand water heater review

The Ecosmart ECO 27 is the most popular electric tankless water heater on the market – and for good reason too. Thanks to Ecosmart’s self-modulating technology, this unit will deliver you hot water in the most eco-friendly way possible; while at the same time not putting a huge dent in your wallet (compared to most units).

Because the ECO 27 runs on electricity (and not natural gas or propane) you’ll save even more money due to not having to worry about the installation of pipes for venting. However, because this unit only runs on electricity – it’s not quite as powerful as its gas or propane counterpart.

For this reason, electric on-demand water heaters are better suited for homes that don’t experience the need for hot water at high flow rates, such as: small houses, apartments, condos, cabins etc. Areas with really low inlet water temperature may want to avoid electric units as well.


According to Ecosmart, using this water heater can save you up to 50% on your costs associated with heating water. The reason the ECO 27 is so cost efficient is due its advanced, self-modulating technology. Essentially, this 27KW (92,000 BTU) electric tankless water heater is actually made up of three separate 9KW water heaters. So if you were to use only a small amount of hot water – such as turning on the sink – then you’ll only have use 9 or 18KW of energy, and not the full 27.

While the ECO 27 (or any electric model) is probably not the best fit for your home if you live somewhere that’s regularly cold, it works exceptionally well if you live somewhere that is fairly warm all year-round.

With an inlet water temperature of 40°F, you can only expect somewhere around 2.8 GPM of hot water at a time; which is maybe enough to run a shower and a sink both at once. On the other hand, with an inlet water temperature of 70°F, you can expect somewhere around 5.4 GPM of hot water at a time, which should be enough to run two showers at once – or even a shower and the dish washer/washing machine both at the same time.

Main Features

  • Self-modulating technology – This technology helps you to save money on your electricity bill by forcing the unit to consume less power when heating only a small amount of water.
  • Digital display – The digital display is a nifty feature since it allows you to see the exact temperature that the water heater is set too. You can even adjust the temperature in 1 degree increments at a time.
  • Great design – While you may not spend a lot of time staring at your water heater (I hope), a lot of consumers are very pleased with the aesthetic design of this unit; as it’s definitely nicer to look at than some old, discolored tank. Not to mention it saves you a whole lot of space.
  • Lifetime Warranty – This unit comes with a lifetime warranty as long as you get it installed by a certified professional.

 Installation Tips

Before buying an electric tankless water heater, you first need to make sure your home has the electrical capacity to do so. If not, you may be in for a rude awakening when you have to upgrade the entire electrical service in your home just to use your fancy new water heater.

While Ecosmart may state the ECO 27 only requires a 200 Amp service panel, you also need to make sure it can handle an additional amperage draw of 112.5 Amps – as well as have six slots available for the three 40 Amp double pole breakers. If you’re not an experienced electrician, we highly recommend you hire one to ensure your home meets the electrical requirements before buying this product.

Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater

review of the Stiebel Eltron Tempra 29

Another electric on-demand water heater the consumer reviews seem to love is the Stiebel Eltron Tempra 29 Plus. While Stiebel Eltron does have an even more powerful unit (the Tempra 36 Plus), we decided to review the former model instead since it only requires a minimum 200 Amp electrical panel, and not a minimum 300 Amp electrical panel like the Tempra 36. This will allow you to better compare this unit to the ECO 27.


This Tempra 29 Plus is a 28.8 KW (98,270 BTU) electric tankless water heater that’s built in a way similar to the ECO 27 – each having three separate water heaters built inside. This causes the unit to be extremely efficient (99% to be exact) by forcing each heating element to engage only when necessary. This high level of efficiency equals out to around 15-20% savings compared to your typical electric-tank water heater.

Another impressive feat is this unit’s ability to function at either 240-volts or 208-volts – depending on the electrical capabilities of your household. Assuming you’re running this unit at its max capability of 240-volts, you can expect around 3 GPM of hot water at an inlet water temperature of 40°F, and around 5.7 GPM of hot water at an inlet water temperature of 70°F. You can even adjust the temperature anywhere between 86 to 125°F, depending on your liking; although around 107°F is what’s typically recommended to avoid scalding.

Main Features

  • Tempra Advanced Flow Control – This feature keeps the water from turning cold whenever the demand of hot water is too high. Instead, the Advanced Flow Control simply lowers the output of water, while keeping the temperature exactly the same. This feature is the bread and butter of this water heater.
  • Digital Temperature Display – The digital display makes it extremely easy to see the exact temperature at all times.
  • 3/7 Year Warranty – If professionally installed, this unit comes with a 3 year warranty against defects in workmanship materials and a 7- year warranty against leakage.

Installation Tips

As previously stated, your home will require a minimum 200 Amp breaker box in order for this unit to operate. You’ll also need space for three 50 Amp breakers – as well as the ability to handle and additional amperage draw of 120 Amps.

Once again, we recommend you hire a certified electrician to ensure your homes electrical service is up the task. This is extremely important with any electric on demand water heater; as they’re more likely to use a lot of electricity compared to their gas or propane counterparts.

Rinnai RU98EP Outdoor Condensing Tankless Propane Water Heater

If you currently have a 40 gallon tank water heater in your home, chances are it has an efficiency rating of around 60% or less. By upgrading to a non-condensing tankless water heater, your home would then have the ability to heat water at an average efficiency rating of 82%.

While an increase in efficiency of 20-25% will surely save you money over time, you can save even more money by upgrading to a condensing tankless model instead.

Because condensing tankless water heaters work by utilizing the heat of the exhaust gas to warm up a secondary heat exchanger, they’re actually able to reach efficiency ratings of up to 95% or more. With a non-condensing model, the exhaust gas is simply wasted by being forced out of the water heater.


Not only is this water heater extremely efficient, but extremely powerful as well. The Rinnai RU98EP has a BTU input of 15,200 to 199,000 BTU per hour, and can even supply hot water to your home at 9.8 GPM (at a 35° rise in water temperature).

If a 75° rise in water temperature is needed, the RU98EP can still manage to deliver 5 GPM of hot water to your home – making this unit a great option if live up north.

The best part about this unit, however, is definitely its high level of efficiency. With an efficiency rating of 95%, this tankless water heater will not only help you save money, but also the environment around you as well.

Thanks to the commercial-grade heat exchanger, you can even use the RU98EP for both residential and commercial applications. The EZconnect feature also allows you to connect two of the RU98EP units together at one time; or you can buy the MSB-M master controller and connect 3 or more units together if a large flow rate of hot water is required.

 Main Features

  • Circ-Logic recirculation program – This program allows you to save money on your recirculation system by setting an external pump to operate at pre-set intervals and temperatures.
  • Scale control system – A specialized cartridge is used to reduce the corrosion of lime scale in your unit by delivering a special blend of compounds into the water stream. This system helps extend the lifespan of the unit as well as reduce the amount of maintenance needed.
  • Temperature lock – Prevents any change to the water temperature that isn’t authorized.
  • Digital temperature control – Easily control the temperature of the water by using the MC-91-2US digital controller.
  • EZConnect – Connect two units together by using the EZConnect feature. If you want to connect three or more units together

Installation Tips

Besides higher efficiency, one of the main benefits of buying a condensing tankless water heater is being able to use less expensive venting materials, such as PVC or polypropylene. On the other hand, if you were to purchase a non-condensing model, you would instead be forced to use category III stainless steel venting – which is much more expensive.

Fortunately, since the RU98EP is an outdoor tankless water heater – no venting is required. However, you can still get an indoor condensing model (such as the RU98IN) if the high price of stainless steel venting is what turned you away from getting an indoor tankless water heater in the first place.

Another benefit of getting a Rinnai tankless water heater is that an isolation valve comes included with every unit.  This Webstone Lead-free Isolator Valve Kit will allow you to preform easy maintenance whenever needed.

Eccotemp I12-LP Indoor Propane Tankless Water Heater



While this unit may not be very powerful, it’s perfect for situations when only a low flow rate of hot water is needed. If you have a small vacation home – such as a cabin, cottage or RV – then the Eccotemp I12-LP may just be for you.

This aesthetically pleasing model may give the illusion of being very expensive, but don’t let its looks fool you. The Eccotemp I12-LP is one of the most affordable tankless water heaters you can buy, and yet it performs like a much more expensive model – without the high flow rate of hot water of course.

Even though this particular model is built to run off propane, you can buy a natural gas model as well. So no matter what form of gas you have available – you’ll be good to go!


With a BTU input of 25,000 – 80,000 BTU per hour, the Eccotemp I12-LP is competing on the same level as the most advanced electric tankless water heaters on the market.

However, in order to buy an electric tankless water heater – you first have to make sure your home meets the proper electrical requirements to do so. In many situations, it’s simply much easier to use natural gas or propane.

In terms of flow rate, you can expect up to 3 GPM with a rise in temperature of 35-40°F, and 1.5 GPM with a rise in temperature of 77°F. Because the output of hot water may not be enough at times, Eccotemp decided to include a flow meter sensor in the I12 series. The flow meter sensor works by reducing the flow rate whenever necessary to ensure the water temperature constantly remains the same.

Another impressive feat of the Eccotemp I12-LP is its high level of efficiency. Not only does this unit have an efficiency rating of 89%, but it also consumes only 2 watts of power when idol, and 1.07 Amps during operation.

Main Features

  • Sleek black gorilla glass casing – The black gorilla glass casing makes the Eccotemp I12-LP one of the best looking tankless water heaters on the market.
  • Child locking technology – Forces you to press the child lock for 3 seconds before allowing you to change the temperature. Great feature for added safety.
  • Touch screen and LCD temperature display – Touch screen controls help you easily adjust the temperature and LCD temperature display shows you the output water temperature and flow rate in GPM.

Installation Tips

Included with the i12-LP is a horizontal stainless steel vent kit to help lower the cost of installation. The vent kit only includes a 90° elbow and a two foot pipe so other venting materials are still required.

It’s also important you make sure that you live under 5,500 feet in elevation if you’re buying this water heater – as it’s not recommended to be used any higher.


Buyers Guide: Choosing the Right Size for Your Home

Tankless water heaters can be installed in many locations such as a home or business, and some are even portable. They are typically the size of any ordinary medicine cabinet or smaller, meaning you can install them in spaces such as closets or even under a sink. However, each water heater is designed to only provide so much hot water depending on the size of the unit. There are those that work great for offices/businesses that only need to provide a small amount of hot water for sinks and such, and there are other tankless water heaters that can provide enough hot water for a large family with a big household.

There are 3 main factors to be accounted for when choosing an on demand water heater: incoming water temperature, maximum desired flow rate, and whether you want a natural gas, propane, or electric model. To make this whole process easier for you let me walk you through each of the steps so you can find the top on demand water heater for your needs.

Step 1: Figure out Your Inlet Water Temperature

To make sure you get the right sized unit you’ll need to figure out how cold your inlet water temperature can get in your area. You then want to figure out the temperature rise in water that the tankless model you will need to produce in order to make sure you don’t lose out on maximum GPM (gallons per minute). Since the average hot water temperature that your home requires should be around 110°F, this means you’ll need a unit that can produce a 60° temperature rise if you’re cold water temperature is around 50°. To find the temperature of your water just use a thermometer or search online.

Step 2: Choose between Gas, Electric or Propane

When looking for a tankless unit make sure to keep the climate of your area in mind, as the colder the water is, the more powerful of a tankless water heater you will need. If you live in a cold climate, you’re better off getting a natural gas or propane model as they are more powerful and efficient. If you live in a warm climate though you can probably get away with using an electric tankless heater and be fine all year round depending on how much hot water you use.

The reason electric models don’t function as well in the northern climate is because they lose too much GPM when a high rise in water temperature is needed. If you do want to buy a gas or propane unit you’ll need to look at the BTU (British thermal units) of each model you’re looking to buy. The higher the BTU a unit has the more water it can heat, or at least heat the water to a higher degrees. If you decide to go with gas or propane model you’ll need to make sure your area has it readily available and proper venting will also need to be done.

Step 3: Decide the Maximum GPM You Will Need

To be certain you won’t ever run out of hot water you need to make sure that you never exceed the maximum gallons per minute that your unit can produce. If there is certain time of the day when a lot of water is being used, such as before bedtime when most people are taking showers, and maybe even washing dishes, then you’ll need to evaluate the GPM for that time of day.

Shower Bathroom Sink Kitchen Sink Dishwasher Washing Machine Bathtub
1.5 – 2.5 0.5 – 1.5 1.5 – 4.0 1.5 – 2.5 1.5 – 3.0 3.0 – 5.0

Above I have made a table giving you a general idea of the GPM of different water appliances. Use this list to get a basic idea of the max GPM your tankless water heater will need to be a perfect fit for your household.


Benefits of Choosing an On-Demand Water Heater

It doesn’t take long to notice that on demand water heaters include many benefits and features that conventional tanks miss out on. Although initially defective, tankless heaters have come quite a long way; the way in which they were designed allows them to be cost-effective, energy efficient, and durable.

Once you really understand what a tankless water heater is capable of and the advantages that come with switching over from a conventional tank, it’ll be clear to you why they’re a real winner and the right choice for your home.


Both in design and in cost, instantaneous water heaters excel in efficiency. The “on demand” technology that these machines use only require them to be on simultaneously with a hot water valve. Once someone turns the hot water valve off, the tankless water heater will proceed to shut off as well. What this means, however, is lots of energy savings. Even with some of the best models being able to pump out 9 gallons per minute, you’ll save about half off of your utility bill each and every month. To top it off, you can expect to receive a $300 federal rebate.


The size of a typical medicine cabinet, tankless water heaters can be installed out of the way in small spaces such as closets, attics, under sinks, and in crawl spaces. Although, you can still choose to install them in other places such as garages, or even outdoors if your model is able. Opposite to belief, these machines send hot water to the needed sink, shower, dishwasher, or laundry appliance almost instantly, in a matter of just seconds. Plus, the hot water is never ending; since the water is heated on demand, rather than stored, there is no limit to the amount of hot water that can be produced. This is great for families who find themselves bickering over who gets to hop in the shower next.


Instantaneous water heaters feature very few problems, even less now than ever before. Over time, they’ve solved the unexpected, short bursts of cold water issue, along with several other minor mishaps. On the other hand, if something ever does go wrong with your tankless water heater it is more than likely easily fixed or a part that is affordable to replace. Conventional tanks can potentially flood, costing you thousands in damage and repairs. Meanwhile, since there is no tank to be ruptured with tankless technology, it is impossible for this to ever happen. You can expect your tankless water heater to receive a lifespan of 20 or more years.


The fact that instantaneous water heaters are on stand-by 90% of the time is already quite helpful to the environment since they’re using as little energy as possible, but tankless machines go much further than that. They produce as little greenhouse gas emissions into the air as possible, with electric models producing none at all. Many tankless water heater companies, such as Ecosmart, specialize in providing environment friendly products to their consumers.

Clean & Safe

Tankless water heaters are the best because they don’t build up rust or scale like conventional tanks do. This means you’re constantly receiving, fresh, clean water to bathe and cook with. As if it couldn’t get better, their also equipped with tons of safety features that vary from brand to brand. Many of them even come with a remote to easily control the unit whenever needed.