There is nothing worse than getting blasted with cold water halfway through your shower. Environmental and financial reasons aside, I think this is selfishly the main reason I’m interested in a tankless water heater. But those first two reasons definitely apply as well: the best tankless water heaters only use the amount of energy needed and therefore can save up to 50% in water heating costs. They are also super space efficient, freeing up floor space for more storage in your garage.
Buying a tankless water heater seems like a no-brainer, but finding the best one proves more difficult. With lots of technical information, it can be confusing and intimidating to pick the right one. That’s where we come in. We’ve done the research for you and compiled our best water heater reviews.
To make this research as approachable as possible, below is a comparison chart followed by in depth reviews. You’ll find product links along the way to check current pricing and/or purchase one for your home’s specific size and needs. You’re one purchase away from never running out of hot water again.
Best Tankless Water Heater Reviews Comparison Chart
|Name||Max Flow||Energy Source||Efficiency||Rating|
|EcoSmart ECO 27 Electric|
Best of 2017 - Editor's Choice
|6.0 GPM||Electric||99.8%||9.7/10||CHECK PRICE|
Great Safety/Protection Features
|6.6 GPM||Natural Gas / Propane||82.0%||9.4/10||CHECK PRICE|
Great for Smaller Homes
|4.8 GPM||Propane||79.0%||9.0/10||CHECK PRICE|
|Stiebel Eltron Tempra 24 Plus|
Made in Germany
|4.68 GPM||Electric||99.0%||9.6/10||CHECK PRICE|
|Electric SCR2 Titan N-120|
Best on a Budget
|4.0 GPM||Electric||99.5%||9.1/10||CHECK PRICE|
Great for Manufactured Homes
|7.5 GPM||Natural Gas / Propane||82.0%||9.3/10||CHECK PRICE|
|Marey Power Gas 10L|
No Electricity Required
|3.1 GPM||Propane||87.0%||9.0/10||CHECK PRICE|
Great for Mid-Sized Homes
|6.4 GPM||Natural Gas||82.0%||9.3/10||CHECK PRICE|
|BOSCH Tronic 6000 C (WH17)|
Very Low Maintenance
|2.3 GPM||N/A||N/A||8.9/10||CHECK PRICE|
Best Brand Overall
|6.6 GPM||Natural Gas / Propane||93.0%||9.6/10||CHECK PRICE|
1. EcoSmart ECO 27 Electric – Best of 2017 – Editor’s Choice
Although all of the units on our list are topnotch, the EcoSmart ECO 27 seems to check most of the boxes and be the best rounded unit that would fulfill most needs. For this reason, it gets our coveted Editor’s Choice award. What we love about this particular unit is that it’s configured for both cold climates (lower flow rates) or warmer climates (high flow rates). Where some other tankless water heaters could not handle cold water, the ECO 27 can handle temperatures as low as 37°F. Not only can it handle those low temperatures, but it can still output almost 3 gallons per minute at them, and up to 6 gallons per minute of toasty warm water when the incoming water starts at a higher temperature. Because of its ability to process a wide temperature range of incoming water, this unit can be utilized all over the United States, even in the north.
Unlike some of the other units on the market, the ECO 27 is a fully electric tankless water heater, which means no natural gas or venting necessary. Adding to this, it has EcoSmart’s patented self modulating technology, which allows the unit to regulate exactly how much energy is needed to heat the amount of hot water needed. This is great for our environment, since it uses the minimal amount of energy needed and since it doesn’t rely on any sort of natural gas. Practically speaking for the buyer, because of its self modulating technology, the ECO 27 can save upwards of 50 percent on water heating costs. With that kind of return, the investment definitely seems worthwhile.
This unit is so intelligent that it will actually ignore faucet drips and won’t send hot water to drippy faucets; the minimum flow to start the unit is 1/4 GPM. Its energy efficiency has been calculated at 99.8%, which indicates how much of the fuel is converted to heat by the appliance. Most units rank in at about 78% – 87% efficiency; the ECO 27’s rating is phenomenally high. For these reasons the unit is both UL (an independent, not-for-profit product safety testing and certification organization that has been testing products for public safety for more than a century) and CSA (Canadian Standards Association, which provides product testing and certification services for electrical, mechanical, plumbing, gas and a variety of other products) certified.
As one of the largest electric tankless water heaters on the market, it can handle a larger volume of water. At the bottom of its flow (2.7 GPM) in nearly freezing cold temperatures, the ECO 27 can handle up to two showers running simultaneously without running out of hot water. At the top of its flow capacity (6.0 GPM) in warmer temperatures, the ECO 27 is capable of running a whopping four showers and one sink simultaneously without running out of hot water. Its larger capacity also makes the ECO 27 well-suited for large Roman-style or Jacuzzi tubs that generally have more demanding water usage needs.
Because the unit is purely electrical, the following electrical capacity requirements are necessary: 27 kW, 240 volts, Single phase, 3 x 40 required breakers, 112.5 maximum power draw (Amps), 3 x 8 AWG required wire.
The unit itself has very manageable dimensions at 17 x 17 x3.75 inches and 13.75 pounds. It can be mounted on the wall to free up floor space for other storage. We love the durability of the ECO 27, made of copper and stainless steel, which makes for a sleek design. It uses three 9 KW standard Emerson electric heating elements with brass tops to prevent electrolysis as well as a copper heat exchanger. These ensure easily replaceable elements if and when maintenance is required. Finally, on the front of the unit is a digital temperature control that allows you to set your temperature in increments of 1 degree, anywhere from 80°F – 140°F. It also supports an inexpensive and waterproof remote control thermostat. It connects to the unit with telephone wire and is perfect for a location next to your sink or shower.
Based on everything written so far, it’s clear that this is a quality unit and definitely deserves to be on our best tankless water heaters review post. What makes it our editor’s choice, however, are the reasonable price and the technical support offered. EcoSmart offers a Lifetime Warranty on the electronics, exchanger and element. The warranty only covers cost of heater and does not cover labor or any incidental damages, but this is still a very impressive warranty. Please note that the unit must be installed by a professional for the warranty to apply. Because of the intricate nature of this installation, we recommend a professional installation anyway. Whether or not you decide to pay for a professional to install your tankless water heater, be sure to purchase these items for the installation process: Aqua-Pure AP430SS Hot Water System Protector and Watts LFTWH-FT-HCN Service Valve Kit for Tankless Water Heater. These items are necessary for maintenance, which is straightforward and simple (huge plus!). All you’ll need is a Phillips screwdriver—gone are the days of pipe wrenches and fiberglass insulation to deal with. Lastly, you have the option to purchase a 2- or 3-year optional protection plan at a very reasonable cost.
2. Takagi T-KJr2-IN-NG – Great Safety and Consumer Protection Features
Compact and sleek, the Takagi T-KJr2 is the smallest unit in the Takagi line-up with dimensions of 13.8 x 6.7 x 20.3 inches and a weight of 38 pounds. The beautifully compact unit has an ANSI (American National Standards Institute) Z21.10 certified design. It is perfectly built for light residential (such as small homes or apartment units) and radiant heating applications.
The unit runs on natural gas, with a gas intake of 140,000 BTU. It is also fully modulating, meaning that it monitors and adjusts in order to reduce temperature fluctuations in the water. In order to achieve this consistency, the unit is outfitted with inlet and outlet thermistors to monitor and maintain the temperature. This subsequently increases the fuel efficiency, and the T-KJr2 boasts an impressive 82% energy efficiency rating. The fuel is used more efficiently, reducing your energy cost, and it does so without condensing the gas into water vapor. The unit is sufficiently energy efficient to warrant its AHRI (Air-Conditioning, Heating, and Refrigeration Institute) certification, a company whose aim is to help save energy, improve productivity, and ensure a better environment.
Although this unit is smaller (perfect for a two-bathroom home), it is mighty in power. It ties the Noritz unit (reviewed below) for the highest max water flow rate on our tankless water heaters review. In warmer climates, it can reach a hot water flow output of 6.6 gallons per minute. We also love the it comes with a power cord and a remote control, so you can adjust the output water temperature without having to go to the unit itself.
Because of its use of gas, the T-KJr2 must be vented using a 4-inch category III stainless steel venting unit. It can’t share a vent stack with any other appliance and must be vented horizontally to a side vent. Because this unit was designed specifically for indoor use, it shouldn’t be mounted outside. Although venting is required, consumers need not fear about nitrogen oxide emissions; it has been certified low NOx by the SCAQMD (South Coast Air Quality Management District) with a NOx output of less than 14ng/J or 20ppm.
Where Takagi really makes a mark is with its topnotch safety and consumer protection features. The unit includes a built-in freeze protection, a manual hi-limit temperature reset, an overheat cutoff fuse (so you don’t have to worry about the unit combusting or burning out), and a flame sensor. As for the buyer’s protection, as long as the unit has been installed by a professional, Takagi offers a 15-year limited warranty on the heat exchanger in residential applications and a 5-year limited warranty on all plans. You can also purchase a 2- or 3-Year protection plan on top of what the standard warranty will cover.
3. Eccotemp FVI-12-LP – Great for Smaller Homes
Don’t have a big budget for a tankless water heater? Don’t have a natural gas line? Don’t want to use a ton of electricity to power it? Then the Eccotemp FVI-12-LP high capacity propane tankless water heater is for you. At a compact 15 x 4 x 24 inches and 33 pounds, this unit is perfect for vacation cabins, cottages, and smaller homes. Since it is run on liquid propane, there no need to have a natural gas line which, again, makes it a better bet for vacation cabins or cottages.
While not the most powerful unit in our top ten water heaters review, it definitely does a great job of producing hot water on demand. Only using gas when hot water is on, it takes in 25,000 to 74,500 BTUs and has a maximum water flow rate at 4.8 gallons per minute with best performance at 2.3 or 3.6 gallons per minutes. Since most shower heads use no more than 2 gallons per minute, this unit definitely supplies a sufficient amount of hot water for 1-2 appliances being used simultaneously. The minimum flow rate is 0.68 gallons per minute, which means that the water need not be on full blast to get hot water out of the faucet. The FVI-12-LP offers precise, manual temperature and water flow adjustment with digital controls on the unit as well as a fully separate gas control.
The unit also boasts an impressive 79% energy factor, pulling only 2 watts and 1.07 amps during operation. It plugs into a standard 120V electrical outlet and comes with UL-listed electrical components (a global independent safety science company with more than a century of expertise innovating safety solutions). Additionally, this unit can be used with 20 pound to 100 pound propane tank (tank and hose with regulator not included).
What is best about the unit, aside from the propane tank and hose, is that it comes fully ready to be installed indoors. Included with the actual unit is a stainless steel vent for safe, efficient power ventilation; because you’re not dealing with a natural gas line, the FVI-12-LP is also simpler to install. However, as it still involves tapping into the water line, we do recommend enlisting a professional for installation. This also ensures that the two year warranty will not be voided due to incorrect installation. Adding to this, the buyer also has the option to purchase a 2- or 3-year protection plan above and beyond the warranty. The company also offers 24/7 technical support available toll free at 866-356-1992.
As with all tankless water heaters, some maintenance is required. The FVI-12-LP must be cleaned and descaled quarterly to avoid lime and sediment buildup within the heater. Failure to do so can void the warranty. Eccotemp offers their Eccotemp EZ-Flush System Descaler Kit to make maintenance much easier and to ensure a clean, energy efficient, long lasting heater. Other accessories that are useful with this unit include the SHURFLO (255-213) 1/2″ Twist-On Pipe Strainer and the SHURflo 4008-101-E65 3.0 Revolution Water Pump.
4. Stiebel Eltron Tempra 24 Plus – Made in Germany
Manufactured in Germany, the Stiebel Eltron Tempra 24 Plus is definitely as stylish and technologically advanced as the luxury cars coming from the same region. One of the most compact designs on our tankless water heaters review—with dimensions of only 21.5 x 19.5 x 8.8 inches and weighing a feather light 15.4 pounds—this unit can fit almost anywhere. Because it is a purely electric unit, no natural gas and therefore no venting is required. This further adds to the variety of places where the unit can be mounted and the amount of space that is saved. The Tempra 24 Plus is also extremely sturdy and durable with seismic proof construction—making this a great choice for earthquake prone locations like California. The copper sheathed heating element is housed in a copper cylinder for added durability. Finally, the unit comes with an easy to read digital display that allows the user a thermostatic control range from 86-140°F. Aesthetically, the Tempra 24 Plus is a definite win.
Functionally, the unit does not disappoint either. The Tempra 24 Plus is arguably the most technologically advanced tankless water heater available on the market today. The whole Tempra series has been completely redesigned both inside and out, including upgraded heavy-duty electronics, a simple single flow sensor design, a hinged cover for easy access, and Advanced Flow Control for the Tempra Plus. More on Advanced Flow Control later, but the advanced technological design of the unit makes it one of the most energy efficient on our list. With an incredible 99% energy efficiency rating, the unit will save at least 15-20% and up to 30% (in kilowatts per hour) on your energy bill, compared to the energy required for a conventional tank water heater. The main energy saving feature of the Tempra 24 Plus is its self-modulating control. This control allows the unit to regulate exactly how much energy is needed to heat the amount of hot water needed. In other words, the unit uses just enough energy to get the job done, and switches into power save mode when it has reached its target. Moreover, because of the tankless design, no standby heat is lost.
Now for the Tempra 24 Plus’ exclusive Advanced Flow Control feature: simply put, it ensures a constant temperature output no matter how great the hot water demand is. It automatically maintains consistent temperatures by slightly reducing flow, thereby fully eliminating aggravating temperature changes (AKA when your shower goes freezing). This particular unit is sized to provides hot water at a consistent temperature for up to 2 bathrooms in warm climates, or 1-2 bathroom in cool climates. It has enough power to provide an incredible 92° temperature rise at 1.5 gallons per minute. Since most showerheads have an output of no more than 2 gallons per minute, the Tempra 24 Plus is able to provide piping hot showers in even the most frigid of climates. Other notable technological features include its exclusive design that prevents dry firing, an electronic switch that allows for nearly silent operation, and a high temperature limit with a manual reset.
As an exclusively electric powered unit, the Tempra 24 Plus does require a 240 or 208-Volt outlet as well as a recommended minimum of 150 total amp service, with 2 separate, dedicated 50 amp circuits. Because electricity and potentially wiring is involved, professional installation is recommended. In addition to the unit and the professional installation, be sure to also purchase an Aqua-Pure AP430SS Hot Water System Protector and a Watts LFTWH-FT-HCN Service Valve Kit for Tankless Water Heater for installation and maintenance. You also have the option to purchase a 2- or 3-Year protection plan which will cover you above what the warranty will. Stiebel Eltron provides a 7 year leakage and a 3 year limited parts warranty.
Lastly, a quick word on the manufacturer of the Tempra 24 Plus—Stiebel Eltron. They actually invented tankless electric water heating technology more than 90 years ago and are still considered the industry pioneer and world leader. They provide an engineering and manufacturing tradition of excellence which brings a source of comfort and reliability. As previously mentioned, their German design and manufacturing are topnotch. Any questions can be directed to the company itself at 800-582-8423.
5. Electric SCR2 Titan N-120 – Best on a Budget
As one our most budget friendly and compact (10 x 12 x 5 inches and only 7.3 pounds), the electric American made Titan N-120 tankless water heater is definitely a purchase worth considering. This model has long been the most popular tankless water heater developed and sold by Titan. Run completely on electricity, there are some electrical requirements: 60 Double Pole or 6 AWG wire (2-1 type, 2 hots + ground), 11.8 kW, 220 / 240 volts, and 54 maximum power draw (Amps). Because these requirements are not substantial and due to the unit’s compact nature, this model is extremely versatile. It has been successfully utilized in a range of locations including houses, apartments, hospitals, campers, and restaurants. This practical and versatile design has received the ANSI (American National Standards Institute) Z, 10.03 certification.
Perhaps slightly less powerful than some of the other units on our top ten tankless water heaters review, the Titan N-120 is highly recommended for homes with one to three bathrooms in areas with warm climates where the incoming water temperature is above 65° degrees Fahrenheit. In these warmer climates, it reaches a max water flow output of 4.0 gallons per minute. It also boasts a very low activation flow rate of 0.4 gallons per minute. This means that you can get hot water to your faucet without having to turn it on full blast.
The Titan N-120 is part of the larger SCR2 series that incorporates new space age technology. A major feature of this upgrade is the faster and more accurate temperature sampling system, which means warm water is brought to the tap more quickly. This analog microprocessor samples input and output temperatures 21 times per second. This results in less water wasted and contributes to the system’s impressive 99.5% energy efficiency rating. It definitely helps that at rest, the Titan N-120 uses no power at all.
In addition to these features, the Titan N-120 also boasts many protective features. The manual re-settable thermostat and the newly added air/water deferential analyzing system prevents “dry starts” or “dry fires”, which is when a water heater isn’t completely full of water when electric power is applied. The result is that the upper heating element will burn out. The deferential analyzing system therefore ensures that the unit is full before activating. With brass and copper casing to protect the dual inconel nichrome heating element, it is an incredibly durable unit. The construction also makes the Titan N-120 an ideal choice for locations where mineral deposits are present in the water. These features contribute to why the unit has been UL (an independent, not-for-profit product safety testing and certification organization that has been testing products for public safety for more than a century) certified.
Because the system is electric and requires no venting, the installation process is much more straightforward. However, the electrical load necessary may vary. For this reason and to prevent any potential flooding, we do recommend professional installation. Professional installation will also ensure that the warranty is not voided. Titan provides a one-year limited warranty on electrical components and a 10-year limited warranty on water components. You also have the option to purchase a 2- or 3-year protection plan above and beyond the warranty at the time of purchase.
6. Rinnai RL75iN – Great for Manufactured Homes
If you’re looking for a tankless water heater that runs on gas and is built for power and speed, then the Rinnai RL75iN is definitely your best bet. Pumping out 7.5 gallons per minute at its maximum flow rate in warmer climates, the RL75iN has, by far, the highest maximum flow rate of all the units on our top ten tankless water heaters review. It also has an incredibly low minimum flow rate of 0.26 gallons per minute and a minimum activation flow rate of 0.40 gallons per minute. This simply means that the user can still get hot water even if they are only demanding a very small amount of water.
It is sized ideally for a two- or three-bedroom home and can be programmed for a temperature of 98°F – 140°F in residential settings. Temperature settings can be set as high as 160°F in commercial settings, but a commercial controller must be purchased separately. If being used within the residential parameters, a MC-91-1US Digital Controller with Error Code Indicator comes standard with purchase of the unit. Regardless of the setting, a temperature lock function prevents accidental or unauthorized changes to water temperature. While the unit is very powerful, it is also efficient. With an 82% energy efficiency, it is EnergyStar certified.
What we love specifically about the RL75iN is that it is compact (9.3 x 14 x 23 inches and 50 pounds) and can be mounted in virtually any room. Because it runs on gas it requires a gas line intake of 10,300 – 180,000 BTU; it must be vented but this unit can vent directly to the outside with a single wall or roof penetration. The venting system uses outside air to create forced combustion and is very safe. And the direct vent sealed combustion vent allows Rinnai to be installed in bathrooms and bedrooms where traditional B-Vent water heaters cannot. The unit is even certified for installation in manufactured (mobile) homes. Although venting is required, the consumer need not worry about nitrogen oxide emissions; it has been certified low NOx by the SCAQMD (South Coast Air Quality Management District) with a NOx output of less than 14ng/J or 20ppm.
As with all tankless water heaters, some maintenance is required. The quality of your water will determine how often the unit will need to be flushed, generally every one or two years. Flushing is accomplished using a small pump to circulate a solution through the unit to dissolve calcium deposits that form inside the heat exchanger. The Webstone 50443PR 3/4-Inch SWT Isolator EXP Tankless Water Heater Service Valve Kit assists in this maintenance and the unit itself has an enhanced scale detection to lessen the possibility of serious, long-term damage to the unit.
Installation for the RL75iN is as straightforward as possible with a tankless water heater. Be sure to also purchase a Rinnai 223182 All-Weather Termination Kit, 21-Inch for the installation process. Because the installation involves gas lines and water, we recommend purchasing expert installation. Nobody wants to deal with a flooded house! And although not explicitly mentioned in this warranty, incorrect installation can often void a warranty. To save ourselves the headache of (1) installing it and (2) proving your installation was correct, we love option to purchase the installation on the spot. Noritz provides limited warranties for 12 years on the heat exchanger, 5 years for the parts, 1 year for labor in residential installations.
7. Marey Power Gas 10L – No Electricity Required (Operates on Batteries)
When there is simply no access to electricity, the Marey Power Gas tankless water heater saves the day—It operates with just two D-cell batteries! The only unit like this on our tankless heaters review article, the Marey Power Gas allows for hot water in even the remotest of locations. For families who live or vacation in rural areas without access to any electricity or with just a small generator, this system allows for them to still take warm showers. The compact design (only 6.9 x 13.6 x 23.6 inches and 21 pounds) further adds to this ability as it can be installed just about anywhere.
The energy-saving design activates with an electric pulse ignition (with just the two batteries), and heats up in seconds. With propane gas as its power, It only uses the gas while water is flowing, meaning you don’t need to fill up your propane tank (20 pound or 100 pound propane tank and hose with regulator purchased separately) as often. Not only does it require no electrical energy, the Marey Power Gas unit has an energy factor of 87%, which is extremely high for a gas tankless water heater.
The unit has a maximum water flow output of 3.1 gallons per minute, but runs the most efficiently at 2.7 gallons per minute. Since most shower heads require no more than 2 gallons per minute, the Marey Power Gas unit is more than sufficient for a small home or cabin. It functions well with low levels of water pressure, from 3.6 to 145.0 PSI.
We appreciate the safety features present in the model, which is important especially if being used in remote locations where service will be more difficult. The unit itself is completely rust-proof, which means that you don’t need to worry about a water leak over time. It is also outfitted with an anti-combustion and gas pressure safety protection. Adding to this, the digital temperature display makes it easy to set the appropriate temperature.
Because the Marey Power Gas requires no electricity and a propane tank, installation is much easier than the other units on our tankless water heaters review. However, it does still require a duct flue vent; for this reason and because the process still involves the risk of flooding your house, professional installation may still be preferred. Professional installation will ensure the validity of the warranty coverage for replacement parts and labor for the first year and of parts thereafter. For installation and subsequent maintenance, other useful purchases include the SHURFLO (255-213) 1/2″ Twist-On Pipe Strainer and the SHURflo 4008-101-E65 3.0 Revolution Water Pump.
8. Rheem RTG-64XLN – Great for Mid-Sized Homes
An American-built, mid-efficiency, tankless natural gas or propane gas water heater designed for continuous hot water, the Rheem RTG-64 is a great choice for most mid-sized homes. With a price point right in the middle range of our top ten best tankless water heaters, you definitely get a lot of bang for your buck with this unit.
As previously mentioned, it was designed for continuous hot water and with a max water flow output of 6.4 gallons per minute in warmer climates, and it definitely delivers on that goal. Built with a powerful all-copper heat exchanger, the RTG-64 boasts an impressive energy efficiency rating of 82%. It is sufficiently energy efficient to warrant its AHRI (Air-Conditioning, Heating, and Refrigeration Institute) certification, a company whose aim is to help save energy, improve productivity, and ensure a better environment. The unit even has an exclusive water savings setting, which decreases the flow of water through the pipes until the temperature reaches the heater’s set temperature; this means that less cold or lukewarm water is sent down the drain. When activated, homeowners can save up to 1,100 gallons of water per year. You simply can’t beat this amazing combination of on-demand, consistent hot water with lower energy costs and lower water consumption. With those two advantages, you can’t afford not to invest in a tankless water heater.
A main complaint about all tankless water heaters is the delay in receiving hot water as well as the “cold water sandwich”. Warm water can be left in the pipes with frequent on/off operation of the water heater, followed directly by colder water that has not yet been reheated. This results in an initial and shocking fluctuation in the water temperature. Rheem works to solve this issue with their hot-start programming, which is a small tweak in the control programming to continue operation for a few minutes after water shut off. This minimizes the fluctuations in the water temperature and basically eliminates the cold water sandwich effect.
Other cool features of the RTG-64 include its high-altitude capability, with compatibility up to 8,400 feet above sea level. For larger homes that require more than one tank, units can be easily connected and operate as one with their EZ-Link Cable. We especially love the unit’s low flow fixture compatibility, which allows users to receive hot water even in very low-demand situations. This tankless water heater boasts an industry first minimum flow rate of 0.26 gallons per minute and a minimum activation flow rate of 0.40 gallons per minute. With the ability of getting hot water with a low demand, gone are the days of having to blast your faucet in order to heat up the water. Even more water cost savings!
At 10 x 14 x 26 inches and only 38 pounds, the RTG-64 is low profile and easy to fit in around your home. It must be mounted outside, and does not require any venting. Although it may feel less convenient to mount it outdoors, we love that the unit comes standard with an UMC-117 remote control as well as a 10-foot thermostat wire. And so although the unit may be outdoors, you can control the temperature from the comfort of inside your house, and you don’t have to deal with venting.
The unit intakes between 11,000 to 150,000 BTUs of gas and requires 120 volts of hard-wired power. Because of these intricacies, we recommend having a professional install the unit. And although not explicitly mentioned in the warranty, this precautionary step will ensure that the the 1 year labor, 5 years parts, and 12 years heat exchanger limited warranty will remain viable. If you do decide to install the unit yourself, we love that it is outfitted with a 1/2″ gas line compatibility and a self-diagnostic system to easy the installation process. Whichever route you decide, be sure to purchase the Rheem RTG20220AB Webstone Tankless Water Heater Service Valve Kit, Clean Brass which will be necessary to maintain the unit. With the ease of use in mind, Rheem includes a flashing warning code on the unit itself to indicate that a service check should be scheduled. And, as previously noted, the self-diagnostic system makes for easy maintenance and service; learning how to flush out a tankless water heater will also be of use. If you choose to, Rheem also provides the option to purchase a 2- or 3- year protection plan above and beyond the warranty when you buy the unit.
Even though the unit will be mounted outside, the concern about nitrogen oxide emissions is still a real one. Rheem took this into serious consideration when they designed the RTG-64 to be an ultra-low NOx unit. It meets the requirements of SCAQMD (South Coast Air Quality Management District) rule 1146.2. Other safety features include their exclusive “Guardian OFW” (overheat film wrap), which protects the heat exchanger, as well as the freeze protection to -30°F. The unit’s digital display shows temperature setting and maintenance codes to make usage and service as simple as possible.
9. BOSCH Tronic 6000 C (WH17) – Very Low Maintenance
If you only have a small house and a semi-tight budget, but want a powerful water heater, then the Bosch WH17 Tronic 6000C is your best bet. Most suited for the southern region of the United States, this heater has the capacity to provide for multiple appliances at 2.3 gallons per minute for a one-bathroom home or similarly sized space. For colder regions, the Bosch WH27 6000C is recommended.
The Tronic WH17 6000C has an incredibly compact design, with dimensions of just 4.5 x 15.5 x 12.5 inches and weighing only 18.7 pounds. Because of the heater’s versatile shape and lightweight design, it can be installed virtually anywhere inside the home. This makes it the perfect solution for smaller homes, commercial spaces, garage apartments, small investment properties, and in-law suites. Especially if being installed in one of these secondary homes, we love that the price point is mid-range and won’t break the bank.
A fully electric unit, the Tronic WH17 6000C requires absolutely no venting; this again, provides a wider range of options for installation. It is also extremely energy efficient, with 97% thermal efficiency and effectively zero standby loss. Standby losses are losses in energy that occur due to keeping the hot water standing by in a tank or keeping your water heater ready to fire again at a moment’s notice. Because of the Tronic WH17 6000C’s incredibly compact design and therefore less surface area, BOSCH was able to get standby losses to pretty much zero. This is great for the environment and also for your electricity bill. The best part is, you don’t have to sacrifice the convenience of warm water when you want it.
Although small and budget friendly, the technology within the Tronic WH17 6000C is impressive and true to the BOSCH reputation. The heating elements are fully polymer encased to ensure efficient heat transfer. The heating element is capable of modulation, to maintain a constant output temperature. Also equipped with a built-in flow sensor, consistency is one of the most impressive aspects of the system. The user is able to control the output temperature with an external control knob. Our two favorite features, however, have to do with the water itself. First, a filter is installed on the inlet, to further purify the water coming through your tap. And, finally, BOSCH has innovated a scale prevention technology that enhances scale resistance. This minimizes the maintenance for the user and extends the life of the tankless water heater.
The Bosch WH17 Tronic 6000C requires professional hardwiring installation and requires minimal electrical circuit breaker service to the home of 80-amps (2 x 40 A). It also requires 17.3 kW and 8 AWG (4 conductors + ground). The unit requires significantly less electricity that some of the more powerful units on our top ten best tankless heaters review. This will also ensure the warranty of the unit, which covers 10 years for the heating module and 1 year for the parts. The buyer also has the option to purchase a 2- or 3-year protection plan above and beyond the warranty.
10. Noritz NRC661-DV-NG – Best Brand Overall
Before getting to this great tankless water heater, we have to say a few words about the company, Noritz. They have been an innovator in the water heating industry for over 60 years and even introduced the first modern, electronically controlled tankless water heater in 1981. Since they they have remained a leader in both energy savings and topnotch hot water delivery.They definitely have an eye for innovation, energy savings, and consumer convenience. All three of these are definite keys for producing one of the best tankless water heaters on the market.
Now to the Noritz NRC661. Long story short, we love this unit. It runs on either natural gas or propane and is fully condensing. This means that they are able to achieve a really high efficiency (using most of the gas and not wasting much) by condensing water vapor in the exhaust gas in order to recover its latent (leftover) heat of vaporization. The NRC661 has an efficiency rating of 93%, meaning that very little of the gas is wasted. And that means a lower gas bill for you. The unit is so energy efficient that it has been certified by EnergyStar.
Depending on the frequency and amount of use, standard gas consumption for the unit ranges from 15,000 BTUh to 120,000 BTUh. Although it runs on gas, the unit has a low NOx design, meaning that it minimizes nitrogen oxide emissions, which is better for the environment and your household. The NRC661 has been certified low NOx by the SCAQMD (South Coast Air Quality Management District) with a NOx output of less than 14ng/J or 20ppm.
Because the tankless water heater utilizes gas as its energy source, venting is required. To mount the unit indoors, the NRC661 comes with a special plastic flue adapter that is compatible with both 3” Schedule 40 and 80 PVC/CPVC pipe. If those standards won’t work in your particular space, the unit can also be converted to a non-direct vent model with the use of a Conversion Kit. If neither of these options seem preferable and you’d rather not deal with venting at all, the NRC661 has the great option of being Outdoor mounted. A 6 foot power cord is included with the unit, to make mounting easy wherever you choose. And at a compact 13.8 x 6.7 x 23.6 inch size and 38 pound weight, there should be plenty of mounting options, keeping your floor free for other storage. In fact, the NRC661 has an ANSI (American National Standards Institute) Z21.10.3 and a CSA (Canadian Standards Association) 4.3 certified design.
Installation for the NRC661 is as straightforward as possible with a tankless water heater. Be sure to also purchase a Noritz IK-WV-200-1-TH-LF 3/4-Inch Lead-Free Threaded Tankless Isolation Valve Kit with 500,000 BTU and Aqua-Pure AP430SS Hot Water System Protector for the installation process and subsequent maintenance of the unit. We recommend professional installation, as installing tankless water heaters is a bit more complicated and involves dealing with water. Nobody wants water intrusion! And although not explicitly mentioned in this warranty, incorrect installation can often void a warranty. To save ourselves the headache of (1) installing it and (2) proving your installation was correct, we love option to purchase the installation on the spot. Noritz includes an impressive 12-year (or 6500 operational hours, whichever occurs first) limited heat exchanger warranty (for residential use only) and a 5-year limited parts warranty. You also have the great option to purchase a 2- or 3-year protection plan.
The unit itself is made of a durable steel casing with a polyester coating. We like the sleek but understated off white look, and find that it blends easily with drywall or outdoor house siding/stucco. The unit has a built in display that allows the user to preset the output temperature to either 120°F, 135°F, or 140°F. We also love the safety features installed in the unit, including a flame sensor, an overheat prevention device, a lightning protection device, freeze protection, condensate overfill (in the event of venting malfunction), fan rotation detector, and a temperature lockout. The unit also allows for adjustments due to high elevations. The NRC661 is a fantastic unit that meets a lot of varying needs, and we simply love it.
Best Tankless Water Heater Buyer’s Guide
Although they require a bigger upfront investment, tankless water heaters definitely save money in the long run. According to Energy.gov, “For homes that use 41 gallons or less of hot water daily, demand (or tankless) water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters.” They are usually quite compact, taking up very little space and having the ability to be installed in more places—sometimes even outside on a wall. They also last twenty or more years, which is almost double a traditional water heater’s life. And, perhaps the most importantly, they deliver hot water on demand, providing at least two or three gallons of hot water per minute on demand.
These reasons are quite compelling for investing in a tankless water heater. However, because they do require a bigger upfront investment, it’s important to do your research and find the best unit for your home. Above you’ll find our top ten tankless water heaters comparison chart and review, which can help you narrow down the best unit for your specific needs. Below we go further into the details of what to consider when making your decision.
Tankless water heaters come in two main varieties: electric and gas. Gas tankless water heaters may require natural gas, propane gas, or may be compatible for both.
Electric tankless water heaters tend to be the most energy efficient and have more flexibility in regards to installation location, since venting is required. They do require more electricity than gas powered models and are sometimes less powerful.
Every electrical tankless water heater will have electrical load specification. Be sure to check those in comparison to what your home is capable of before purchasing. We included these details in the review of each of the electric units on our top ten tankless water heaters article.
Gas tankless water heaters require much less electricity (and in the case of Marey Power Gas 10L 2.7 GPM Propane Gas Digital Panel Tankless Water Heater requires no electricity but only 2 D batteries). They do, however, need a gas source—either natural gas line or propane—to fuel the heater. Gas heaters are slightly less energy efficient than electric versions, but all of the units on our list boast a very impressive energy factor.
Not required in electrical units, but all gas units will require venting to the outside unless they are capable of being mounted directly outdoors. There are various types of vents which may work better or worse for your particular space.
Non Direct Vent Indoor (Fan Assisted)
These vents pull oxygen needed for combustion from inside your home and use an electric fan (or blower) to push flue gases to the outdoors. These type of vents allow for both horizontal and vertical venting.
Direct Vent Indoor (Fan Assisted Sealed Combustion)
Outdoor air is supplied directly to the gas burner for combustion. The heater has a sealed cover, and doesn’t use any air from the installation space. The unit achieves this by having two separate pipes or a pipe within a pipe concentrically, which runs from the water heater through the wall or roof of the home. One of the pipes is used for fresh air intake and the other for exhaust. This type of venting is generally used when tight construction may cause various appliances to compete for the same air, and is therefore a good space saver. It also can be vented vertically or horizontally.
The water heater receives combustion air from the environment around it and expels exhaust the same way, with no fumes entering the home at all. However these are recommend for warm climates only.
A main reason to invest in tankless water heaters is how much they will save in gas and/or electricity bills. In order to see how energy efficient the unit is, look for the Energy Factor (EF) rating. The EF rating measures how efficiently a unit converts energy into heat as well as how much heat is lost during storage. The higher the EF (as close to 1 as possible), the more energy efficient the unit is.
As previously noted, electric tankless water heaters tend to have the highest EF ratings. Our Editor’s Choice for our top ten best tankless water heaters review, EcoSmart ECO 27 Electric Tankless Water Heater, actually has a 0.998 EF or 99.8% energy efficiency. Be sure to check out our Comparison Chart to see the impressive energy efficiencies of all ten units.
Water Flow and Temperature Rise
The amount of water volume that a tankless water heater is able to produce is offered in gallons per minute (GPM). This water flow is dependent upon the power of the unit’s heating element in conjunction with the temperature of the incoming water. So, water will come out of the tap at your desired temperature (usually around 120 degrees Farenheit) much more quickly in Arizona during the summer than it does in upstate New York during the winter.
For each unit you can find its “temperature rise” and water flow in GPM. For instance, it might be able to raise the water temperature 35 degrees at 4.5 GPM but to raise it 85 degrees the flow would slow to 2.3 GPM. This is much more important to consider for those who live in locations where the ground water gets very cold. In most cases, the max water flow rate will be pretty accurate to what you will experience at home. For this reason, we include this rate on our Tankless Water Heaters Comparison Chart.
For those that do live in colder regions, be sure to look at the maximum temperature rise that the unit is capable of, even if it will be at a slower flow rate.
When figuring out the right size of tankless water heater you need (based on its max GPM water flow), below is a helpful chart that shows the average flow rate for household appliances:
|Kitchen Faucet||3.0 – 7.0 GPM|
|Bathroom Faucet||0.5 – 1.5 GPM|
|Shower||1.0 – 2.0 GPM|
|Dishwasher||1.0 – 2.5 GPM|
|Washing Machine||1.5 – 3.0 GPM|
Keep an eye for certain safety features. Gas units emit some nitrogen oxide. You can look for a low NOx certification, which means that the SCAQMD (South Coast Air Quality Management District) has verified a NOx output of less than 14ng/J or 20ppm. A temperature lock will prevents anyone from accidentally changing the water temperature. Other safety features to look out for include built in freeze protection, a manual hi-limit temperature reset, an overheat cutoff fuse (so you don’t have to worry about the unit combusting or burning out), and a flame sensor.
Certain certifications exist to show energy efficiency, proficient design, and safety. Below are a list of a few that you might encounter:
- UL: An independent, not-for-profit product safety testing and certification organization that has been testing products for public safety for more than a century)
- CSA (Canadian Standards Association): provides product testing and certification services for electrical, mechanical, plumbing, gas and a variety of other products) certified.
- AHRI (Air-Conditioning, Heating, and Refrigeration Institute): A company whose aim is to help save energy, improve productivity, and ensure a better environment
- SCAQMD (South Coast Air Quality Management District): Certifies NOx output of less than 14ng/J or 20ppm
- ANSI (American National Standards Institute): Z, 10.03 certification for design
- EnergyStar: Energy efficiency certification
Warranties are provided for the heating element, for labor, and for other parts. They range from 2 years to a lifetime warranty.
As noted in most of our tankless water heaters reviews, we highly recommend employing professional installation of your unit. Some companies explicitly state that a warranty is only valid if professional installation has been used. Others don’t state it, but can void the warranty if they feel that it has been improperly installed. Aside from the warranty benefits, because tankless water heater installation involves gas or electrical wiring, and because improper installation can result in water flooding into your home, we highly recommend professional installation.