Comparing The Best Tankless Water Heaters

best tankless water heater

If you’ve ever run out of hot water while showering, I think you’ll agree:

There’s almost NOTHING worse than stepping out of the shower shivering and freezing!

A quality tankless water heater, custom-tailored to your family’s hot water needs, will ensure you won’t run out of hot water ever again.

And more:

It’ll even help you save money in the long-term by lowering your monthly electricity costs.

The problem is, there are so many makes and models to choose from it can get overwhelming. That’s why I created this extensive guide to the best tankless water heaters on the market.

If you don’t have the time to read through a lot of reviews and comparisons, I’ll give you my top picks right now. Later on I’ll be diving into each water heater and giving my in-depth review.

  NamePower SourceFlow RateRating 
Best Overall
Stiebel Eltron Tempra 24 PlusElectric4.5 GPM4.8/5Check Price
Best Value
Takagi T-KJr2-IN-NGNatural Gas6.6 GPM4.7/5Check Price
Best Quality
Rheem RTGH-95DVLNNatural Gas9.5 GPM4.7/5Check Price
Energy Efficient
Rinnai RUC98iN Ultra SeriesNatural Gas9.8 GPM4.5/5Check Price
Budget
Ecosmart ECO 18
Electric3 GPM4.4/5Check Price
T

ankless water heaters used to be prohibitively expensive, but they’re only getting cheaper.

Along with their small size compared to their with-tank alternatives, the fact that they never run out of hot water, and their power efficiency leading to lower monthly electricity expenses, I think you’ll agree that they’re a good choice for most home hot water needs.

In this article, I’m going to help you decide which tankless water heater is right for you by providing in-depth reviews of 15 of the absolute best makes and models on the market, divided into categories by their maximum flow rate (the amount of hot water they can provide). This is so you can focus only on the those heaters that provide the right amount of flow for your household’s needs.

Further on you’ll find a detailed buyer’s guide that will teach you about the various features and specifications of on-demand water heaters, and answer common questions you might have.

best whole house tankless water heaters

Best Whole House Tankless Water Heaters

As this size, you’re buying something that will easily service all but the very largest properties. Multiple bathrooms running simultaneously, showers and baths on entirely different ends of the property from the installation point of the unit, all with less temperature fluctuations or drops in normal use.

What this means is you won’t have to worry about drops in pressure or temperature even when everything is in use. So when the kids come home and jump straight in the shower whilst you’ve got the dishwasher and washing machine on, you can be sure that everything will keep on chugging.

At this level, you’re also looking at heating units that are large enough to consider running smaller commercial uses, with options for linking several machines in series to increase outflow, as well as enough hot water output on the larger machines to justify commercial installation.

Tankless Water Heater Comparison Chart

stiebel eltron tempra 24 plus
Stiebel Eltron Tempra 24 Plus
  • 4.8/5 Rating
  • Electric
  • 4.5 GPM
  • Anywhere
stiebel eltron tempra 24 plus

Recommendation

Our top rated instant water heater across all ranges, and also the best electric tankless water heater, the Stiebel Tempra 24 Plus is a fantastic model that just gives and gives. It’s supposed to only put out a maximum of 4.5 gallons per minute, way below the rest of the range and barely enough for two bathrooms, but in practice it easily outperforms this thanks to Stiebels innovative technology. Coupled with the fact that it’s electric rather than gas and it can be installed inside and outside and you’ve got a versatile, powerful unit suitable for pretty much any household.

TECH SPECS

Power source
Electric
Maximum flow
4.5 GPM
Install location
Anywhere
Size
17” x 15” x 5′
Temperature range
86-140F
Energy factor
0.99
Kilowatts
24kW
Volts
240V

Stiebel Eltron Tempra 24 Plus

Stiebel make the most technologically advanced electric water heaters on the market, and it shows. The amount of technology in this system means that even though its raw numbers look much less than the equivalent choices in terms of water flow and heating, it manages to keep up, or even outperform similar water heaters in almost every regard.

For a start, it’s ridiculously efficient, with a 99% energy factor meaning almost no energy is wasted not heating water. This saves you loads of money in the long run. The Tempra series also have advanced flow control modules built in, that automatically regulate water pressure when you start to exceed your systems limits on hot water. What this means is, it will slowly reduce water pressure until it’s stable again, meaning you get the most consistent temperature possible.

It’s built to the same high standard as all Stiebel systems, with excellent all around build quality, high quality, expensive electronics, corrosion resistant internals and seismic proof construction means it will last for years. The warranty is comprehensive, but only lasts 3 years. That’s nothing to worry about though, as the quality is so high that people have had these units for years and never needed anything fixing.

I found it simple to use, with an idiot proof temperature control setup on the front, and I was also surprised by how small it was, barely bigger than a lot of point of use models.

One thing I found excellent is it’s also upgradeable. It’s possible to install more heating elements into this unit, up to a maximum of six, which is incredibly useful if you’re looking for commercial usage, or you’re planning an extension some time in the future and don’t know if your water use might change.

The only real downsides are the slightly more difficult installation, and the hungry electricity requirements compared to some other units. It needs 240V of power and heavy duty wiring, so make sure your property has adequate infrastructure before you buy this. If in doubt, get it checked and installed by a professional.

Overall, the high performance and excellent build quality win out. This is the single most reliable and consistent electric water heater I’ve ever reviewed, and that’s why it’s my number one pick. No matter your situation, this will handle it.

rinnai rl94ep
Rinnai RL94 EP
  • 4.6/5 Rating
  • Propane
  • 9.4 GPM
  • Outdoor
rinnai rl94ep

Recommendation

The Rinnai 94 series are part of the Rinnai Luxury range, aimed at larger homes and commercial usage, and it certainly delivers on that. It’s got a massive maximum output flow of 9.4 gallons per minute, easily enough to deliver hot water for an entire house at peak capacity. For comparison, 9 and a half gallons is four showers running at maximum capacity and the hottest temperature, all at once.

TECH SPECS

Power source
Propane
Maximum flow
9.4 GPM
Install location
Outdoor
Size
9.3” x 14” x 23”
Temperature range
98-140F
Energy factor
0.83

Rinnai RL94 EP

Like a lot of propane based heaters, it’s less efficient than an electric water heater, only 83% energy efficient rather than the near 100% you get with electric, but it’s still efficient enough to qualify for Energy Star compliance and government rebates and tax assistance and far more efficient than even the best tank based water heater.

Fully controllable from the front panel, it’s easy to use and programmable on a 24 hour cycle, great if you know you need hot water at specific times of day, and for greater control there’s also an option for a commercial remote controller.

This is an outside only unit, because it has no exhaust options besides the built in venting slot. Rinnai also make an indoor variant, if that’s something you need.

The internals are really high quality, and it’s got a massive 12 year warranty on the heat exchanger, and a solid 5 years on working parts. It’s easy to service, too, with built in service valves that make access simple, something I don’t see on many heaters.

For a household or small commercial enterprise, the Rinnai 94 is a great choice. With its excellent hot water output and running capacity, and the quality Japanese manufacturing that will last forever, it’s a capable and powerful instant water heater.

rheem rtg 84xln
Rheem RTG-84XLN
  • 4.5/5 Rating
  • Natural Gas
  • 8.4 GPM
  • Outdoor
rheem rtg 84xln

Recommendation

A solid, powerful unit that will easily provide enough hot water for almost any home, with great options for commercial usage, the only downsides to the Rheem are the huge size and only average performance compared to its competitors.

TECH SPECS

Power source
Natural Gas
Maximum flow
8.4 GPM
Install location
Outdoor
Size
27” x 18” x 9.5”
Temperature range
80-140F
Energy factor
0.82
Kilowatts
N/A
Volts
120V

Rheem RTG-84XLN

Putting out 8.4 gallons per minute with a temperature rise of 30 degrees fahrenheit, or 6 gallons per minute with a temperature rise of 45 degrees, the RTG 84 is easily powerful enough for all but the largest of homes.

It runs on natural gas, with a good energy factor of 82 percent that makes it reasonably efficient. Its nothing special, but still better than a water tank. As a natural gas unit, venting is important, but this particular system is low emissions and low nox, so even though it’s an outdoor unit it has options for indoor installation.

One very impressive feature on this is the hot start programming, which minimizes the water temperature fluctuations you normally get when you first turn something on. It also comes with a remote control, for really easy operation.

For commercial use, there are multiple options for series linking, with circuit boards available for 6 and 20 unit chains. It’s also robust, with a 12 year warranty on the heat exchanger and 5 year warranty on everything else.

It is huge, though, and incredibly heavy, especially compared to an electric water heater. That doesn’t detract from the performance, though, and this is a reliable gas heater with good performance that will easily handle the vast majority of properties.

takagi t h3 dv n
Takagi T-H3-DV-N
  • 4.3/5 Rating
  • Natural gas
  • 10 GPM
  • Indoor
takagi t h3 dv n

Recommendation

Takagi make some of the best instant water heaters, and this model is no exception. Powerful, with a huge water flow value of 10 gallons per minute and a high maximum temperature of 185 F, it’s possibly even too powerful for most normal homes. If you have a heavy need for hot water, like an exceptionally large house, or are looking for commercial usage, this is a fantastic choice.

TECH SPECS

Power source
Natural gas
Maximum flow
10 GPM
Install location
Indoor
Size
24.9” x 17.8” x 11.2”
Temperature range
100-185 F
Energy factor
0.95
Kilowatts
N/A
Volts
120V

Takagi T-H3-DV-N

Like all Takagi water heaters, this is a fantastic system, with a wealth of exceptional features that make it powerful, efficient, and an all round excellent choice. For a start, it heats its water to a huge 185 degrees fahrenheit maximum temperature, far hotter than any residential property will ever need.

Its highly efficient at 95%, which is great for a natural gas model, almost approaching the efficiency of electric water heaters. There’s also a built in computerized safety and electronic ignition switch, which means no flickering, always burning pilot light.

One major downside is, because of the function of this water heater, it requires a drain as well as an exhaust vent, which can be a real pain in the ass to install. Needing to find a position that provides adequate drainage for the acidic water it produces can be problematic, especially if you don’t have any suitable existing drains and have to bore one specifically.

It’s also relatively large, and pretty heavy at 60lbs, so it requires a decent mounting surface to make sure that it’s properly fixed. It also requires almost 200,000 BTUs to run this thing at full capacity, so you might need to upgrade your pipes to get it working at full power, ’cause a lot of homes wont have what it needs as standard.

Overall, this is fantastic water heater, but my honest criticism is that it’s too much for most normal situations. There’s almost no situation where a standard house will need as much hot water as this puts out, and if I was looking for an instant water heater for my home, I probably wouldn’t buy this because it’s just too much. But if you do buy this, you won’t regret it. It’s powerful, fast, and packed with technology, making it one of the best out there.

mid range tankless water heaters (whole house   small home)

Mid-Range Tankless Water Heaters (Whole House – Small Home)

At this size, you’re looking at heaters with a general flow rate of around 6 gallons per minute, this means that they can comfortably run several features at once. For example, the number one pick in this category, the Takagi, will easily run everything in two good sized bathrooms at once without struggling.

Normally, this size water heater is powerful enough to replace a conventional water tank for smaller households of two to four people with one or two bathrooms. They’re also more than ample for single rooms and sole point of use, and aren’t particularly expensive either, so it’s easily possible to have more than one in larger houses, setting each one up close to where they’re needed, giving you instant hot water all over your property.

Tankless Water Heater Comparison Chart

takagi t kjr2 in ng
Takagi T-KJr2-IN-NG
  • 4.7/5 Rating
  • Natural gas
  • 6.6 GPM
  • Indoor
takagi t kjr2 in ng

Recommendation

My best value choice, and also the best gas tankless water heater, the Takagi is a compact, powerful natural gas based heater that can easily run two bathrooms at the same time. Cheap, easy to install, and with a great warranty, the Takagi water heater is perfect for smaller households.

TECH SPECS

Power source
Natural gas
Maximum flow
6.6 GPM
Install location
Indoor
Size
20.3” x 13.8” x 6.7”
Temperature range
Energy factor
0.83

Takagi T-KJr2-IN-NG

Considering the price, the Takagi T-KJr2-IN-NG is really powerful, giving you the same performance and hot water flow that you’d get from a 40 gallon water tank. Considering the size of it, this is really impressive, as it’s barely 13 cubic feet total, with a footprint of less than a square foot the smallest in the Takagi range.

In terms of performance, it runs at 6.6 gallons per minute, which is far more than enough to run two showers. At 6.6 gallons it heats water by up to 35 degrees fahrenheit. You can also reduce the flow to 3.3 gallons per minute, enough for even the most greedy shower, to raise the temperature by up to 70 degrees fahrenheit.

Takagi is a Japanese company, and the build quality throughout is exceptional. Just in case anything goes wrong, it’s got a great warranty that covers the heat exchanger for 10 years and other parts for 5. It’s also got an altitude switch, which is good for up to 6000 feet above sea level. Niche, but it’s there.

Bear in mind it’s a natural gas heater, so it needs venting, and you can’t share the exhaust stack with any other gas appliances, which is something to consider when installing.

Overall, the Takagi T-KJr2-IN-NG is a great gas tankless water heater. It’s powerful enough to replace a small water tank in small to medium homes, and cheap enough that you could use it as a point of use heater and still not feel bad.

ecosmart eco 27
Ecosmart ECO 27
  • 4.5/5 Rating
  • Electric
  • 6 GPM
  • Indoor
ecosmart eco 27

Recommendation

With the same massive 99% efficiency rating as every other Ecosmart, and putting out enough hot water to comfortably work with multiple rooms at the same time, the ECO 27 is a solid, effective instant water heater with a range of technology that make it an even better choice than the smaller models.

TECH SPECS

Power source
Electric
Maximum flow
6 GPM
Install location
Indoor
Size
17” x 17” x 3.75”
Temperature range
80-140F
Energy factor
0.998
Kilowatts
27kW
Volts
240V

Ecosmart ECO 27

The ECO 27 is the first Ecosmart model that I feel comfortable saying is a replacement for a conventional water tank. Putting out a solid 6 gallons, this instant heater will comfortably feed two showers plus extras, and works at the same great temperature range as the smaller models, from 80 to 140 degrees fahrenheit.

Another great thing about this is the lowest working temperature, anywhere from 37 degrees fahrenheit, making it ideal for colder climes, and meaning you won’t have to worry when the temperature drops next winter.

It’s full of the same technology Ecosmart puts into all of their heaters. Proprietary self modulating technology that only uses as much energy as needed, excellent and easy to use digital controls that are accurate down to one degree. It’s also got the option for a remote control, which is fantastic in this age of wireless everything.

Like everything but the smallest model in the Ecosmart range, this does requires a minimum of 240V and three 40A electrical breakers to run, but its actual power consumption is low. It’s got three individual water heaters, and each one only switches on when it’s needed, so if you’re only running one faucet or don’t need to heat the water too much, it will only switch on one heater at a time and use a whole lot less energy, saving you even more money.

Solid and dependable, this is a great heater for smaller households, and its all covered by a lifetime warranty, giving you the peace of mind that once it’s in, you’re set and covered, and don’t have to worry about hot water for years to come.

stiebel eltron tempra 20 plus
Stiebel Eltron Tempra 20 Plus
  • 4.4/5 Rating
  • Electric
  • 4.5 GPM
  • Indoor
stiebel eltron tempra 20 plus

Recommendation

Stiebel make the most technologically advanced electric water heaters on the market, and the Tempra 20 Plus is no exception. It’s top of the line and German made, and the advanced flow control means it gives you the most consistent water temperature possible. It’s just a little small compared to the others at this price point, with a slightly lower water flow rate, which affects my rating of it.

TECH SPECS

Power source
Electric
Maximum flow
4.5 GPM
Install location
Indoor
Size
17” x 15 x 5”
Temperature range
86-140F
Energy factor
0.99
Kilowatts
19.2kW
Volts
240V

Stiebel Eltron Tempra 20 Plus

99% efficient, and with Stiebel’s advanced flow control, the Tempra 20 gives you far better performance than the specs say you should. The advanced flow control automatically adjusts water pressure when you exceed the maximum flow, so if for example you’re in the shower and someone turns on the dishwasher, the temperature won’t change and plunge you into freezing water.

There are two built in heating units, which give this a maximum temperature rise of 44 degrees fahrenheit, and it’s got a temperature range of 86 to 140 degrees fahrenheit. This makes it ideal for smaller properties with one or two bathrooms, especially in hotter areas with warmer groundwater.

It’s built to a really high standard, too. German made heavy duty electronics, corrosion resistant internals and seismic proof construction means it will pretty much never go wrong. This is probably a good thing, as the warranty is quite short compared to a lot of others, only 3 years.

Whilst this is a great instant water heater, for just a little bit more outlay you could upgrade to the Tempra 24, which is my vote for the best electric water heater on the market, dollar for dollar.

rinnai v65ep
Rinnai V65 EP
  • 4.4/5 Rating
  • Propane
  • 6.6 GPM
  • Outdoor
rinnai v65ep

Recommendation

The only propane driven instant water heater in this category, and the only one that needs to be placed externally. The Rinnai V65 is a solid heater with consistent performance, but for me the fact that it’s a lot more bother to install and maintain means it might not be worth the hassle, especially when you can get something comparable that runs on mains and can be installed anywhere indoors.

TECH SPECS

Power source
Propane
Maximum flow
6.6 GPM
Install location
Outdoor
Size
23” x 14” x 9”
Temperature range
98-140F
Energy factor
0.82
Kilowatts
NA
Volts
120V

Rinnai V65 EP

Generally, propane is only used for far larger and more powerful instant water heaters than this one. However, there’s nothing stopping companies from making smaller water heaters using propane and still making a quality product, as this one shows.

Rinnai make two models of the V65, the EP, for external use, and the ‘I,’ for internal use. This model is the EP, so it has to be installed externally. This brings a few bonuses, like not requiring venting which saves money and makes installation much easier, as well as saving space in the house. But it also means you have to make sure it’s protected when you’re placing it, as particularly bad weather can affect the operation of the heater and potentially even do damage.

It’s certified safe, with low emissions and environmentally friendly operation, and it’s safe to be installed in mobile homes. There’s no pilot light, too. The ignition is electrically driven, which is safer and more consistent.

In terms of heating, it puts out 6.6 gallons per minute, about the same as the Takagi, our top rated model in this category, but it’s a lot less efficient. Only 82% as opposed to up to the 99% you get on electric models. As it’s placed outside, you’re also going to get a lot more temperature bleed, and as it’s likely to be placed further from the point of operation, it’s going to take a lot longer for hot water to get to where it’s needed. I’ve heard stories of showers taking up to 30 seconds to go from anything except ice cold.

Overall though, this is a good instant propane heater. It’s powerful, and puts out enough hot water for houses with one or two bathrooms. If you need a propane based heater, this is a great choice, but given the option, I’d go electric.

top of the line tankless water heaters (whole house or commercial, high flow, natural gas)

Top Of The Line Tankless Water Heaters (Whole House or Commercial, High Flow, Natural Gas)

At this size, everything is putting out enough hot water to run a normal house all the time. You’ll never have to worry about exceeding your hot water limit, because you won’t have one.

There’s also a lot to love for commercial usage here, with built in or upgradable options for series linking units to increase output flow, as well as huge efficiency across the board.

Bear in mind, systems this size are designed for massive amounts of use and that probably makes them overkill for smaller households of two to four people. If you’re looking for something in that range, you’re probably better off with one of the choices in our Mid-range or Best Water Heaters sections.

If you do have a need for a unit from this range, bear in mind they all run on natural gas, with the vast majority requiring somewhere around 200,000 BTUs delivered to run at maximum efficiency.

Tankless Water Heater Comparison Chart

rheem rtgh 95dvln
Rheem RTGH-95DVLN
  • 4.7/5 Rating
  • Natural gas
  • 9.5 GPM
  • Indoor
rheem rtgh 95dvln

Recommendation

Our choice for the highest quality water heater out there, Rheem have outdone themselves with this model. It puts out enough hot water that any residential users won’t have to worry, it’s really efficient for a natural gas model, and its one of the safest and most reliable models I’ve ever seen.

TECH SPECS

Power source
Natural gas
Maximum flow
9.5 GPM
Install location
Indoor
Size
27.5” x 18.5” x 9.8”
Temperature range
80-140F
Energy factor
0.94
Kilowatts
N/A
Volts
120V

Rheem RTGH-95DVLN

First off, this is one of the most powerful and most efficient natural gas hot water heaters there is, running at over 90% efficiency and putting out almost ten gallons per minute of hot water, which is enough to run two bathrooms and a kitchen full of appliances with ease.

It’s stuffed with safety features, including Rheems patented overheat film wrap that keeps you protected in the event of a heat exchanger breach, (which is obviously bad, because that generally ends up with hot water all over the floor and the inside of the unit.)

The vents are high quality stainless steel, and because it’s a condensing boiler, the exhaust gases are nowhere near as hot when they leave the system, so you can get away with using cheaper venting materials, saving you a few dollars.

It’s also highly recommended for colder climates. Rheem specifically created this thing to fight off the frost as if it was nothing, and it has built in freeze protection that allows it to operate anywhere down to -30C, which is obviously enough unless you’re living in the arctic.

It’s simple to install, with a self diagnostic system that can tell you exactly what’s wrong on the front digital display. The same display you use to control it, and that show you temperature settings and any codes should it go wrong.

It also comes with a remote control in case you wanted to adjust it from a distance, and there are options for expansion, with both six unit and twenty unit manifold control boards available, in case you need to link these together for heavy commercial use. If you’re looking to expand on this and don’t mind spending a little more cash, there’s also an option to install a recirculation pump, which provides instant hot water as soon as you turn on the tap, rather than having to wait a few seconds like you might otherwise.

Overall, Rheem have made one of the best natural gas powered water heaters out there. It’s incredibly powerful, to the point of overkill for most normal properties, it’s packed with technology that makes it safer and more efficient than pretty much any comparable model, and it puts out more than enough hot water for almost any situation. That’s why it’s our choice for best quality hot water heater on the market.

rinnai ruc98in ultra
Rinnai RUC98in Ultra Series
  • 4.5/5 Rating
  • Natural gas
  • 9.8 GPM
  • Indoor
rinnai ruc98in ultra

Recommendation

Our most efficient choice, Rinnai’s Ultra RUC98 is also energy star compliant, meaning if you’re looking to upgrade to a tankless water heater to save yourself money in the long run, this is the best choice to make. It’s expensive up front, sure, but this system will just keeps paying back the longer you have it.

TECH SPECS

Power source
Natural gas
Maximum flow
9.8 GPM
Install location
Indoor
Size
26′ x 18.5” x 10′
Temperature range
98-140F
Energy factor
0.96
Kilowatts
N/A
Volts
120V

Rinnai RUC98in Ultra Series

These models are part of Rinnai’s ultra range, the highest class of instant water heaters they make and the ones designed for the heaviest amount of work. According to the manufacturers, this system will cope with houses with up to four bathrooms needing hot water, so if you’re looking for a serious product that can cope with the largest properties, this is a good choice.

They’re safe and efficient. Like I’ve already said, it’s energy star compliant, and has between 95 and 98% efficiency, which is fantastic for a natural gas heater. It averages out somewhere around 96% efficiency, which would be good even for an electric water heater, the most efficient kind.

There’s no pilot light, instead relying on electric ignition, and emissions are incredibly low, making venting easy. It’s also got a hot water temperature lock, multiple electronic controls for water temperature and flow, and diagnostic systems that make it simple to service and repair in case of faults.

If you’re in an area with hard water problems, there’s enhanced scale protection built in, and it’s made of high quality materials so it’s pretty scale resistant.

With the best efficiency to performance of every instant water heater I’ve ever looked at, as well as multiple other excellent features and Rinnai’s quality of build throughout, the RUC98 Ultra is easy to recommend. On top of all of this, there’s also an outdoor model, so no matter what you need, this can provide.

rheem ecosense 8 4 gpm
Rheem Ecosense 8.4
  • 4.4/5 Rating
  • Natural gas
  • 8.4 GPM
  • Indoor
rheem ecosense 8 4 gpm

Recommendation

A solid, well performing water heater that only falls short compared to the others in this list, the Ecosense 84 still performs well enough to provide hot water for all but the largest houses, and gives the same solid, reliable performance we’ve come to expect from Rheem products.

TECH SPECS

Power source
Natural gas
Maximum flow
8.4 GPM
Install location
Indoor
Size
27.5′ x 18.5” x 9.75”
Temperature range
85-140F
Energy factor
0.82
Kilowatts
N/A
Volts
120V

Rheem Ecosense 8.4

Compared to both the Rinnai and the larger Rheem model above, the Ecosense 84 seems a little lackluster. But then it would, because they’re designed for different things. The Ecosense line is specifically designed to be a more economical model that still performs well enough to deal with the rigors of daily life on all but the largest properties.

You’ve got a flow of 8.4 gallons per minute at a temperature rise of 30 degrees fahrenheit, easily enough to run two bathrooms and other appliances together, and 6.6 gallons per minute at a hotter temperature rise of 45 degrees, which is still enough to run two bathrooms simultaneously.

It’s got freeze protection down to minus 30, the same as the best of Rheem’s indoor heating models, and a solid and easy to use digital control suite, which makes using it a breeze and servicing and repairs simple.

Honestly, if you’re just looking for a reliable whole house tankless water heater, this is a good choice. It’s not too expensive, it’s powerful enough to service all but the largest of houses, and it’s one of the highest rated and best reviewed systems out there.

noritz nr981 svng
Noritz NR981
  • 4.0/5 Rating
  • Natural gas
  • 9.8 GPM
  • Indoor
noritz nr981 svng

Recommendation

A heavy duty but basic instant water heater by American brand Noritz, the NR981 will comfortably service even the largest and greediest houses, but it’s unfortunately lacking in every other department.

TECH SPECS

Power source
Natural gas
Maximum flow
9.8 GPM
Install location
Indoor
Size
23.6” x 13.8” x 9.4”
Temperature range
100-140F
Energy factor
0.84
Kilowatts
Volts
120V

Noritz NR981

Putting out 9.8 gallons per minute, this instant heater is powerful, but unfortunately relatively inefficient at just 84%. It’s pretty small, and quite light for a system with this amount of output, so it will be easy to find a place for it in your home.

There’s also freeze protection, high altitude adjustments and safety lock outs, but unfortunately, that’s all it really has going for it.

There’s no digital controls, and you have to open it up to adjust it. Worse, the temperature settings only go from 100 to 140 degrees, and are adjustable only in 5 degree increments. Comparing this to the swish front mounted digital panels and degree by degree adjustments I’m used to and it’s actually quite embarrassing. We’ve got systems here a third the price that are more technologically advanced than this one!

Worse, it both looks and feels old. This doesn’t just apply to Noritz’s products, either. I know this isn’t a way to judge a company, but their website seems incredibly unprofessional. It just left a bad taste in my mouth to see a company that should be projecting professionalism using something that hasn’t been updated in years, and I think that’s a fair criticism of everything they do. It works, but it’s nothing flashy.

Compared to everything else above, and especially considering the cost, this really isn’t worth looking at. The world has moved on, and tech of this level is hard to justify.

point of use tankless water heaters (single shower/sink)

Point Of Use Tankless Water Heaters (Single Shower/Sink)

At this size, you’re looking at a heater that can comfortably run a single shower and maybe a faucet, but not much more.

They’re small and light, so easy to place and install, and have a lot less power requirements than larger units, but obviously this affects the output. The majority at this size are also electric, which means a lot less requirements when it comes to placement and exhaust venting, making installation a whole lot easier.

If you’re looking for an instant water heater that can easily run one or two appliances or faucets, or you have a room in your house that’s far enough away that it’s worth getting a separate heating unit plumbed in, then these are ideal.

Tankless Water Heater Comparison Chart

ecosmart eco 18
Ecosmart ECO 18
  • 4.4/5 Rating
  • Electric
  • 3 GPM
  • Indoor only
ecosmart eco 18

Recommendation

My number one budget choice, the Ecosmart ECO 18 has one of the highest energy efficiency ratings I’ve ever seen. It’s maximum flow rating of 3 gallons per minute is good for a heater this size and easily powerful enough for single showers and other point of use situations.

TECH SPECS

Power source
Electric
Maximum flow
3 GPM
Install location
Indoor only
Size
17”x 14”x 3.75”
Temperature range
80-140F
Energy factor
0.998
Kilowatts
18
Volts
240V

Ecosmart ECO 18

According to the manufacturer’s guide 3 gallons per minute should be able to run two low flow showers at the same time. In my experience, it’s more realistic to assume that you’ll be able to run one shower and possibly a faucet without any drop in pressure or temperature changes, which makes this ideal for single bathrooms, garage setups and summer cottages.

Fully electrically powered, it’s set by a digital temperature gauge that runs from 80 to 140 F in one degree increments, which I found really easy to use. It’s also tiny, small enough to be installed under a sink fitting or on a wall without any issues, which is good because this is an indoor only water heater.

It’s covered by a lifetime warranty in case something goes wrong, and you’re set for all electronics, the heat exchanger and the element, basically any of the expensive working parts. Bear in mind that you’re only covered if the machine is installed by a licensed professional, so for all you DIYers, that’s something to watch out for.

The most impressive thing about this though is its 99.8% energy efficiency rating. Bear in mind conventional tank heaters can be lucky to get 80% efficiency, so you can imagine how much money this will save once it’s installed. It is worth noting that to install this you require a minimum of 150A and two 40A double pole breakers, so as always check the wiring and electrical situation in your property to make sure it’s sufficient, as having to unexpectedly upgrade your house’s wiring can be expensive.

However, most properties should easily be able to accommodate those requirements, and for a budget point of service model, I honestly don’t think there’s a better product out there.

ecosmart eco 11
Ecosmart ECO 11
  • 4.2/5 Rating
  • Electric
  • 2 GPM
  • Indoors only
ecosmart eco 11

Recommendation

The little brother to the Ecosmart ECO 18, the ECO 11 retains its same fantastic 99% energy efficiency, and puts out enough hot water to consistently run a single shower or pair of faucets. If you’re looking for a heater designed specifically for a single installation point, this is a solid choice.

TECH SPECS

Power source
Electric
Maximum flow
2 GPM
Install location
Indoors only
Size
11.5” x 8” x 3.75”
Temperature range
80-140F
Energy factor
0.998
Kilowatts
13KW
Volts
240V

Ecosmart ECO 11

Made with the same robust quality and attention to detail as everything in the Ecosmart range, the ECO 11 is a well designed little unit that will give you solid, long lasting performance, if you pay attention to its downsides.

Firstly, this is a single point of use heater only. It puts out 2 gallons per minute, which is ample for a faucet, and is good enough for the vast majority of showers. It’s going to struggle for anything more than that, so don’t go thinking you can replace your house’s water tank with this.

It’s tiny, obviously designed with the use in mind, so fitting it around where it’s intended to be used will be easy. Like I said in the buyers guide, when you’re installing tankless water heaters, you want to get them as close to the area they’ll be used as possible to get your hot water flowing as quickly as you can.

It’s fully adjustable, with electronic controls that are set in single degrees with a good temperature range of 80 to 140 degrees fahrenheit, and all its working parts are made of the highest quality material. The warranty covers all the electrical parts as well as the heating element, too. Something to consider though, like all Ecosmart products, the warranty is only valid if the heater was installed by a certified professional.

This unit is designed to be used in areas of about 67F and above. It will function in areas colder than this, but obviously performance suffers. It also needs a 240V electrical supply, so as always make sure that you’ve got the capacity to run what you’re buying. But if you’re looking for a small instant water heater that you can install easily for a single area in your house, this is a good, reliable choice. It’s just a shame that for a little bit more money, you can grab an ECO 18, which is that much more powerful.

marey power gas
Marey Power Gas 10L
  • 3.9/5 Rating
  • Natural Gas
  • 3.1 GPM
  • Indoor only
marey power gas

Recommendation

This Marey Power Gas instant water heater has solid performance equivalent to the ECO 18, our top rated point of use model. So why have we rated it lower? Simple. Because it runs on natural gas, it’s so much bigger and bulkier, as well as requiring an exhaust vent, and for a unit this size I don’t think it’s worth it. However, it’s still a powerful little water heater, and does the job it needs to do.

TECH SPECS

Power source
Natural Gas
Maximum flow
3.1 GPM
Install location
Indoor only
Size
24” x 14” x 7”
Temperature range
Dependent on groundwater temperature
Energy factor
0.87

Marey Power Gas 10L

The first thing that struck me about this heater was its size. It’s legitimately massive, two feet tall, and almost 10 kilos in weight. As it runs on natural gas, you’re also going to have to make allowances for the necessary exhaust vent when you install it.

However, if you can get past this you’ll find a powerful and relatively efficient little water heater that’s more than good enough for single point of usage setups, and potentially powerful enough to run several points, for example a shower and a faucet, at the same time.

Its maximum output is three gallons a minute. A shower uses between 1.5 and 2.5 gallons per minute, depending on the model, so this is easily enough. It’s also got a solid efficiency rating of up to 87%, which is far higher than even the most efficient tank based water heaters, as well as an auto igniter that runs off of standard batteries.

One advantage of this heater is you can run it off the grid, so to speak. A propane tank and some batteries is all it needs, so if you’ve got, for example, a hunting lodge or lakeside cottage that needs hot water, this is much easier than getting electric lines run out to it and cheaper than a generator setup. It’s also got a low pressure startup, so you don’t need to worry about pressurised water lines, which also makes this a great choice for installation on upper floors.

It’s also pretty easy to install, especially for someone that knows what they’re doing. The manual that comes with it is easy to understand and completely comprehensive, and it’s all covered with a 5 year warranty.

Overall, this is a good portable water heater, but it doesn’t perform any better than electrically powered variants, which are generally much easier to install and use and a lot more convenient. But if you’re looking for gas, or you need a heater that can’t be electrically powered, this is a great choice.

How To Choose The Tankless Water Heater That’s Right For Your Home

The Definitive Buyer’s Guide

tankless water heater buyers guide

Why would I choose a tankless water heater over a conventional storage boiler tank?

why would i choose a tankless water heater over a conventional storage boiler tank?There are several major reasons.

First and perhaps the most obvious; in the long term it will save you money.

Yes, I know, instant water heaters are a lot more expensive to buy, and they’re also more expensive to install, but only in the short term. Because they only heat water when you need it, tankless water heaters end up slashing massive chunks from your heating bill, and over the course of a few years, these savings can really add up.

Imagine cutting 30% from your heating and water bill over the twenty year lifespan of your new water heater. How much money would that save?

Second, they’re a lot more convenient. A shower can easily use over two gallons of hot water per minute, so a small water tank, like a 40 gallon model, could easily be exhausted just by that one shower if everybody needs to jump in. Say, if you’re going out?

Because the heat exchangers in tankless water heaters actually heat up the water running through it as you use it, it gives you an endless supply, no matter how much or how little you use.

Third, tankless water heaters are a lot less space intensive. Some models are small enough to be mounted right at the point of use, for example under a sink that requires instant hot water, as soon as you switch on the tap, and even the biggest are still smaller than even the smallest water tank.

There are other considerations, as well. For example, some models have options for indoor and outdoor installation, meaning you could easily free up some space in your garage or loft by putting it outside. Some even have the option to be run off the grid, meaning you could potentially have a setup that supplies hot water to an out of the way woodland cabin or lakeside summer holiday home without running mains cables all the way out to it.

Are there any downsides to tankless water heaters over water tank boilers?

Of course. No technology is perfect.

For one, as we’ve already mentioned, because they are so much more impressive in performance and operation, tankless water heaters are more expensive, both in initial purchase cost and installation costs.

Second, depending on the model you buy and its power needs, you might need to consider venting requirements, drainage, and/or electrical needs.

Third, there’s the cold water sandwich problem. You hear about this one a lot from detractors of instant water heaters, but in my opinion it’s nothing to worry about unless you’ve got an enormous property, and even then there are ways around it.

Finally, if you decide to install a tankless water heater over a water tank, you will have a limit on how much hot water you can use across everything in your house. This is why it’s important to look at how much hot water you need, and work out how many gallons per minute your new heater will need to give you.

Should I replace my existing water heater with a tankless model?

The question on everybody’s mind. Like everything in life, there are advantages and disadvantages to both options, and even a few years ago it would have been easy to say it depends on your circumstances, but today even homes with small water and heating bills should seriously consider looking at a tankless water heating option.

As always, it’s down to personal circumstances, but advances in technology and lowering costs mean that tankless water heaters are becoming more efficient and much more attractive every year.

How do I know how much hot water I need?

A good rule of thumb is around 3 gallons per minute per bathroom. This should cover general usage with no problems. As an example, a shower running hot requires somewhere between 1.5 and 2.5 gallons per minute to operate.

If you want to be absolutely sure, every device in your house that requires a plumbed in water supply will have a rating by its manufacturer, which should be available in the documentation or on the manufacturer’s website. This should be expressed as gallons per minute, telling you how much water it needs to operate. So add up the values of everything in your house that is likely to be running together, and that’s how much water you need.

It’s always better to go slightly higher than you think you need, if possible. Nothing is worse than hot water being drawn from the shower you’re currently in to feed something else in your house.

A lot of manufacturers provide handy guides on groundwater temperature and the maximum flow of all of their units, and what this should power. A good example of this is on Ecosmart website for the ECO18, one of our top rated point of use instant water heaters, and can be found here.

What is maximum flow? (Also known as Flow rate, output flow, or GPM)

Maximum flow is how much hot water your instant water heater is capable of outputting at full power. It’s expressed in gallons per minute, (GPM) at a specific temperature rise, eg, 6 GPM at 30 F temperature rise.

What’s a maximum temperature rise?

The temperature rise is how many degrees your water heater will increase the temperature of the water running through your pipes. Higher temperature rise is obviously better, as this means your water heater will be able to increase the temperature of your groundwater further, which can be especially important in colder climates, which will have naturally colder groundwater.

Some more expensive models of tankless water heater have multiple temperature options, with the ability to reduce your maximum flow to increase the temperature of your water.

What does my heater’s efficiency rating and energy factor mean?

Your heater’s efficiency rating tells you how much of the energy that the system requires to run goes into heating the water as opposed to being lost to the outside environment. This means the higher the efficiency rating, the better. Efficiency rating is also expressed as energy factor. They mean exactly the same thing, but efficiency rating is normally given as a percentage, and energy factor will be given as a decimal figure.

When it comes to power sources, all instant water heaters have different efficiency ratings, with electrically powered instant heaters generally being the most efficient, followed by natural gas, and lastly propane.

As a quick rule of thumb for efficiency:
80%+ is okay. 85%+ is good. 90%+ is excellent. 95%+ is exceptional.

So how do tankless water heaters work?

so how do tankless water heaters work?It’s actually deceptively simple. Once your new heater is plumbed in, the water in your pipes will run directly through a set of pipes inside the unit.

When you need hot water, the heater turns on, and uses either a gas burner (if it runs on propane or natural gas) or an electric element (if it’s electric) to heat the water as it runs through it.

This heated water runs through the pipes to exactly where it’s needed, and as soon as you switch off the hot water, the heater also instantly switches off and stops heating the water in your pipes.

Because it heats water as it runs through the heater, rather than slowly heating it over time like a water tank, this is how it gives you endless hot water, and also why knowing the temperature rise of your unit is important.

It’s also this as-needed operation that saves you money. As the water in your central heating system is only being heated when you’ve got a need for it, your instant water heater uses almost no energy when its on standby.

So how much do tankless water heaters really cost?

The real answer is, it depends.

In the reviews, we looked at water heaters that can cost as little as $250, and others that can cost seven or eight times that. Bear in mind they generally cost two or three times as much as an equivalent performance storage heater model.

In terms of installation costs, again it depends. You’re looking at several hundred dollars, at least, and you’re going to want to get it installed by a licensed professional, as a good number of manufacturers won’t honor warranties if they aren’t.

There are other considerations that could ramp up the cost as well. Needing to create exhaust venting space, changing wiring and circuit breakers if your house isn’t up to electric standards. These things can all run expensive.

As always, we recommend you look at everything as deeply and as critically as you can. Add up the costs involved and balance that against the convenience of having endless amounts of hot water at your fingertips and the savings you will make in bills.

What’s the difference between gas and electric power for tankless water heaters?

Electric tankless water heaters are generally smaller, cheaper and less powerful than units that run off of gas. Because they don’t need venting for exhaust gases, they’re a lot easier to install indoors, easier to maintain, and safer too.

Gas heaters are more powerful, but less efficient than electric water heaters. This is balanced by the fact that they’re generally around 10% cheaper to run. Gas instant heaters also have a much higher range of outputs than electric heaters, from smaller models up to the very largest and most powerful. (All of the most powerful models with the highest flow in our review range are gas powered.) Obviously, because they run on gas, they’ll also need to be supplied with this to run.

In general, electric models are ideal for smaller uses. Point of use, single room and small households should probably consider electric power.

Gas power, being far more powerful but also requiring more maintenance and installation considerations, are excellent for houses that need the very best performance, large amounts of hot water delivered quickly and efficiently. Gas driven instant water heaters are also excellent for commercial uses, and a lot of the higher level models actually have control board availability that allow you to link them in series to increase output flow even more.

What about natural gas versus propane? Which should I choose?

In my experience, it’s not which should I choose, but more which is available.

If you’re planning on running your water heater off of natural gas, that means that there has to be availability in your area. In general, natural gas is cleaner and much more efficient than propane in operation, as well as being cheaper per unit in general.

Instead of being delivered via gas main, propane will be delivered from a propane tank on your property. This means propane is by far the easiest variety of instant water heater to set up, especially if you are planning on installing it outside and have to worry less about venting. The price you pay for this is less efficiency and greater running costs.

If you have the option, natural gas is both cheaper and better for the environment in the long run, and if I had the choice of both, I’d choose natural gas.

The model I’m looking at says it is a condensing water heater. What does that mean?

Gas based water heaters produce hot gases as part of their operation, and require an exhaust vent to get rid of this by-product. A condensing heater has technology that captures some of the heat of this exhaust gas. This reduces the temperature of the exhaust gases, making venting requirements a lot easier, and then uses this energy in the system itself to heat the water in your pipes, making the system much more efficient.

There are slight downsides, however. The condensed runoff water has to have specific drainage requirements as it’s slightly acidic, and condensing heaters cost a little bit more up front. In the long term though, it’s usually an investment that will pay off.

What is the cold water sandwich problem?

A conventional storage based water heater works by constantly heating the water in the tank, which is connected to your central heating, so the water in the pipes in the rest of your house will also slowly heat up to the same temperature as the water in your tank.

Instant water heaters don’t do this. Instead, they only begin to heat the water in your system when you switch them on, which is what saves you all that money on energy bills. What this does mean though, is because the heater is only heats up the water running through the heat exchangers inside the unit, it can’t heat the cold water sitting in the pipes between the heater and whatever you’ve just switched on, so this cold water has to be flushed out of the system before the hot water can come through.

This only ever becomes a problem in larger houses where the water heater is a large distance from water fixtures, meaning there is a larger volume of pipe between the heater and the fixture. In most normal circumstances, there will only ever be a few seconds of cold water flow, then your water will come out as hot as you want it for as long as you need it to.

What are the effects of hard water on a tankless water heater? How will this affect maintenance?

The water flowing through your new water heater will create calcium deposits, or scale, whether it’s considered ‘hard water’ or not. You will have to descale your water heater at least once every three years, which should be done with the general servicing of the system.

If the water in your area is particularly hard, you may need to descale your water heater more often, potentially up to once a year.

4 Responses

  1. Alex says:

    If I have a water softener installed (before the water gets to the heater, of course), does that eliminate or just reduce the necessary frequency of descaling?

    • edanb says:

      Hey Alex, thanks for stopping by! While using a water softener before the heater will definitely reduce the frequency of descaling, it won’t eliminate the need completely. The frequency can drop to once every 4 or 5 years, so I’d say it’s a clear win. Also, most units will void their warranty if the unit is not descaled periodically, which is another reason to get it done every so often.

  2. Jaimie says:

    It’s a pity you don’t have a donate button! I’d certainly donate to this brilliant blog!
    I guess for now i’ll settle for bookmarking and adding
    your RSS feed to my Google account. I look forward to brand new updates and will talk about this blog with my Facebook group.
    Chat soon!

    • edanb says:

      Hey Jaimie, thanks for the kind words! I’m so happy you found the post useful, and sharing the site with others is thanks enough 🙂

Leave a Reply

Your email address will not be published. Required fields are marked *