Best Tankless Water Heaters: Top Rated Gas and Electric Options For On Demand Hot Water

Home / Best Tankless Water Heaters: Top Rated Gas and Electric Options For On Demand Hot Water

Tankless water heaters are all the rage in the plumbing and heating world right now! They offer substantial energy savings, improved reliability, and a much more compact design than traditional tanked water heaters.

These devices have been popular in Europe and other spots around the world for decades, but they’re just now taking off in America. It’s an exciting time, as more European companies bring their products here, and more American companies get into the market!

However, most buyers don’t really know what they’re looking for when they shop for tankless water heaters. It’s easy to pick the wrong one, and end up frustrated. You’ll also have to deal with the fact that while many companies in the business are producing quality products, just as many are jumping on the bandwagon to catch the zeitgeist without putting in enough design planning and engineering.

We’ll help you navigate the waters of the tankless world in this guide! We’ve rounded up six great tankless water heaters that we think are the best of the best! There are three gas models, and three electric models. They come in all shapes, sizes, and formats, so there’s something here for every home!

Let’s jump right in with a glance at our top three!

EcoSmartStiebel Eltron TempraEccotemp
Our Rating: 4.3
Popularity: Very High
Our Rating: 4.8
Popularity: Medium
Our Rating: 4.4
Popularity: Low
Buy on Amazon
Buy on Amazon
Buy on Amazon

Why You Should Switch To A Tankless Water Heater

Tankless water heaters save lots of space compared to the units that have tanks attached. You’re saving a significant chunk of space in your basement, mudroom, or wherever else you might have installed your old water heater. A tank unit usually takes up a whole corner of the room, at least up to shoulder height. A tankless model can be as small as a board game box! Even the largest units are tiny compared to a bulky water tank.

Since they’re so compact, you can fit tankless water heaters just about anywhere. Any gas unit will have to be ventilated outside or installed outside your house, which makes them slightly more limited, but electric units can fit in cabinets, next to sinks, you name it! They’re much, much easier to fit into your actual living space. You wouldn’t want a massive water tank in your kitchen, but you’ll barely notice having a tankless unit!

They’re also more reliable. Tank water heaters are notorious for going wrong and developing major issues quickly. Tankless water heaters run for years with excellent reliability records. They have longer lifespans than tank models, and they need fewer service visits along the way.

There’s a lot less potential for water damage when a tankless water heater goes awry, too. You can simply shut off the water supply when something comes up. If you’re dealing with a failing old-fashioned water heater, you’ve suddenly got a whole tank’s worth of water damage to contend with.

They provide hot water as long as you want it! With an old-style/tank water heater, you have as much hot water as there is in the tank, and then you have to wait for the machine to catch up to you. A tankless water heater isn’t rated to a set quantity of hot water. Instead, it’s rated for a flow amount, such as 5 GPM (gallons per minute). As long as you don’t go over that limit, you can keep drawing hot water for as long as you want, with no delay and no interruptions. That’s a huge advantage, especially in houses where several people will need to shower one after another, for instance.

They’re much more energy-efficient than the tank options. With a tank model, you’re going to be burning fuel all day long, in order to keep a tank full of water at temperature. It’s not burning fuel like crazy if you’re not using hot water, but you’re still using a steady drip all day. With a tankless water heater, you only use fuel when you’re using water. It’s that simple. According to the US Energy Department, the average fuel savings for a gas unit will be about $108, and the savings for an electric unit will be about $44 every year. Those are just the average figures, too! With a high-efficiency, model, you’ll save even more.

With so many benefits, and with the costs coming down every year, there’s no reason not to go with a tankless model for your new water heater!

Now, let’s get into some reviews!

Best Tankless Reviews For On-Demand Hot Water

Top-Rated Electric Tankless Water Heaters

1. EcoSmart ECO 27

This EcoSmart unit is a very cost-effective choice for people looking for an electric tankless water heater. It’s efficient, effective, and provides a lot of bang for your buck. It might not be as indestructible as the more expensive German-made options, but we think it’s the best of the budget-range electrics.

The Specs:

  • Power requirements: 240V/112.5A electricity, 3-40A breakers
  • Size: 17” x 17” x 3.75”
  • Output Capacity: 2.71-6.59 GPM max.


It’s small but mighty. Under 14 pounds and in a 17” square, it’ll easily fit in a kitchen cabinet, or on the wall wherever your electrical and water hookups are handiest. Previous buyers marveled at how much space they were able to save over their old tanked water heaters!

You get a lot for what you pay! According to EcoSmart’s handy chart, this unit is capable of cranking out from 2.71-6.59 GPM, depending on your area. In the coldest parts of the USA, where inlet temperatures can be as low as 37° F, it’s rated to produce nearly 3 GPM–enough to run a shower and sink simultaneously. In Southern climes, it would be more than enough for the average house, even with several showers running at once.

It’s our cheapest choice for high-demand homes in warm spots, and average to high-demand homes in cold regions. Previous buyers in states like FL and AL said they could easily supply several bathrooms at once or several appliances simultaneously!

It has a digital control panel, which allows you to set hot water temperature to a precise degree setting. You can set the temperature to anything between 80° F and 140° F. Previous buyers liked being able to dial in different settings for different needs. You can turn things up for a load of whites, then just turn down the limiter for your normal shower and sink usage.

It’s made by a company which is very focused on reducing energy use. EcoSmart have integrated self-modulating technology that’s usually not available on such an inexpensive unit. It constantly adjusts the heater to make sure it’s only using as much energy as you’re requesting. This machine is rated to be 99.8% efficient–almost perfect! As a result, it’s rated to save up to 50% on your hot water bills!

It’s cheaper by half of other electric tankless models.

It’s covered by a lifetime warranty! EcoSmart claim to be the only tankless electric manufacturer offering lifetime coverage, and our research indicates that’s true.

It’s also built with modular parts, so as to make for easy repairs. Most previous buyers said that when they ran into minor issues, the company’s tech support were very helpful in talking them through replacing fuses and other components. Judging by more recent reviews, EcoSmart have been improving a lot in the customer service department when it comes to warranty and service claims, too. That was a weak spot for a few years.


Some buyers weren’t thrilled with the output in colder climes. You should always err on the conservative side when you’re looking at output ratings, or you could end up disappointed. Still, a fair number of reviewers in cold spots said the company’s estimates weren’t realistic.

Even the least expensive electric tankless water heaters are as expensive as some midrange gas models. However, you’re dealing with a lower fuel cost over the long term, especially in areas with high natural gas and propane prices.

While electric units have lower startup and installation costs than gas models, you’ll need to pay for a 240V electric hookup if you don’t already have one (most people don’t).

You’ll also have to figure in professional installation costs. The warranty is only valid if the unit is installed by a licensed pro, and buyers who tried the setup themselves said they soon got in over their heads.

This is a budget model, and it’s an imported Chinese make. So, it has a spottier record for reliability than we’d like. It’s nowhere near as consistent as our German-made recommendations.

Some buyers had issues with flickering lights. They advised that you might need to have 200A service to resolve that. Some other buyers had bad experiences with making warranty claims and getting the company to honor repairs and replacements. Others reported that their machines had been going strong for years.

We still think this is a more reliable, durable choice than other budget electrics, but it shouldn’t be considered on par with one of the more expensive Stiebel units, for instance.

2. Stiebel Eltron DHC E12

This Stiebel unit is actually a lot less expensive than the EcoSmart, but it’s also a much smaller water heater with a lower capacity. It’s a good choice for people on a budget who would rather invest in a more reliable, consistent German unit with a lower output than a cheaper, higher-capacity (but less reliable) machine like the EcoSmart. If you’re a low-demand user looking for a small whole-house heater, or someone looking to use a few small water heaters like this around your house, this is very, very good for its size!

The Specs:

  • Power requirements: 208-240V/112.5A electricity, 1 50-60A breaker
  • Size: 7.9” x 14.2” x 4.1”
  • Output Capacity: 1.82-2.34 GPM max. through 1/2” pipes


It’s a Stiebel–the original tankless water heater company. The German makers were the first to put these machines on the market, and they’ve had a reputation for innovation and quality ever since! There’s a reason they’ve got such a strong brand loyalty–these are the best of the best for electric units.

It’s absolutely tiny! This is designed as either a single-application heater (for one bathroom, as an example), or a low-use water heater for a whole house. Since it’s designed for a relatively low output, it can be as compact as can be. It’s just slightly larger than a wall soap dispenser, or a cup dispenser. You can easily get it in a cabinet, even a tight one. Or, since it looks so good, you could mount it right on the wall without it being a big, ugly eyesore.

It might be a small heater, but within its capacity, it’s close to perfect. You’d be hard pressed to find any complaints about this Stiebel besides its low capacity. If you expect to use it for up to 2.34 GPM and no more, you’ll be good as gold. Buyers said it got right up to temperature, modulated smoothly without delays, and supplied up to its capacity even in cold spots!

It’s ideal for people who only use one or two hot water appliances/fixtures at a time. If you live alone, or if your family are good about scheduling and alternating showers, laundry, and other hot water needs, this could easily supply a single-bathroom home.

While this is only rated for up to 2.34, it’s not a rating you should approach with skepticism. That’s not the case with most models, which offer optimistic estimates at best! Even at the lowest inlet temperatures in the country, it’ll still provide 1.82 GPM as hot as you want it. If you’re using super low-flow showers and sinks, reviewers said you could get away with 2 at once in temperate and warmer climes. However, you wouldn’t want to use more than 1.0 GPM shower heads at the same time. In cold areas, this should really be considered a single-fixture heater.

It actually has two different options for wiring and operation. You can use this as either a Stage 1 (7.2 kw) or Stage 2 (9.6 kw) type heater. That’s handy for people who have specific wiring requirements. It also allows people who are just using this for one room to run it on lower power.

As with the EcoSmart, you can adjust the temperature precisely. The Stiebel’s range is between 86° F and 140° F.

There’s a handy safety limiter feature to keep the maximum temperature at 109° F. It’s a great precaution against scalding water.

It’s self-modulating like the EcoSmart, and is just as efficient.

It’s much more reliable than an EcoSmart. This one has an impeccable reliability record, like most Eltron’s. In fact, a lot of people who were frustrated by unreliable or faulty EcoSmart’s commented in their reviews that they replaced the faulty units with Eltron’s. They noted the heavier construction, superior design, and much better reliability.

Overall, buyers agreed you really do get what you pay for with these machines! It has a solid copper heating system, overload and overheating protection, and a number of other features that you just don’t find on cheaper models like the EcoSmart. Oh, and it’s all made in Germany!

It’s covered by a 7 year warranty on leaks, and a 3 year warranty on parts. Unlike the EcoSmart’s warranty coverage, this one is all-inclusive, and backed by customer service with an excellent reputation.

Even though it’s a superior German model, it’s a lot cheaper than the EcoSmart.


While buyers who took the DIY approach said this is very easy to install, we’d still recommend hiring a professional. So, figure in installation costs to your calculations!

It’s not for high-demand houses, unless you’re going to have a few of these running around the house. Make sure you’re not expecting this to produce more than 1.82-2.34 GPM, however you have it set up!

It’s less expensive than the EcoSmart, but mostly because it’s a smaller heater to begin with. This is relatively expensive for its output, but we think it’s worth it in quality.

3. Stiebel Eltron Tempra 24

Stiebel Eltron Tempra 36 Plus

This Stiebel Eltron, the Tempra 24, is our top quality recommendation for an electric unit. It’s more than capable of supplying a whole house with hot water, even if you want to run 2 or 3 things at once. It’s twice as powerful as the smaller Stiebel, and it has even more great features packed in the casing. Think of it as a much more reliable alternative to the EcoSmart. We think that the average homeowner need look no further for a capable, long-lasting electric model!

The Specs:

  • Power requirements: 208-240V/150A electricity, 2X 50-60A breakers
  • Size: 21.5” x 19.5” x 8.8”
  • Output Capacity: 2.52-4.68 GPM max.


It’s got twice the output capacity of the smaller Stiebel, and it can compete with the EcoSmart as well! The EcoSmart might be rated at a slightly higher max output, but most reviewers agreed that those estimates were optimistic at best. The Stiebel on the other hand reliably meets its max ratings!

Even in the coldest climates, it’ll crank out at least 2.52 GPM. That’s more than enough for the average household, even if you want to use two (1 GPM or less) fixtures at once. It can even run two showers with no issues in the coldest climates. If you’re using low-flow heads, you could probably get away with two showers and a third output in temperate and warmer climes.

In most places in the USA, you’ll get more like the maximum 4.68 GPM from this one! That’s ample supply for even multi-bathroom homes, or people who want to do dishes, run laundry, and still have enough hot water for another family member to take a shower.

On the whole, buyers raved about the Eltron’s performance. They were amazed at how quickly it kicked in, as well as how smoothly it adjusted between temperatures. As long as reviewers had needs under the maximum output rating, they had nothing but praise!

Even though it’s so powerful, it’s still relatively compact. This one takes up less than two square feet, and is less than 9” thick.

As with the smaller Stiebel, you can adjust between 84° F and 140° F. It adds a digital display, and a more elaborate control knob, though, which makes it even more intuitive to use. This one also has some pre-marked settings to help you choose the right one for your home. It has the same safety limited for the highest temperature setting, as well.

It has even better self-modulation and flow control than the smaller Stiebel. It’s miles ahead of the EcoSmart! Even if you exceed capacity, the Eltron will simply drop water pressure to compensate, so you can still take a hot shower, albeit at a lower flow rate. Reviewers said they saw substantial savings on energy bills!

It’s just as well-made as the small Stiebel. The heating system is all-copper, the plastic housing is even more sturdy, and the whole thing is equipped with heavy-duty electronics and safety sensors.

Reviewers found it to be incredibly reliable, with many saying they had been running theirs for years without a single hitch! The very few buyers who ran into trouble said they were immediately shipped replacement units or parts with no hassle.

It’s only about $200 more than the EcoSmart, for a machine that will last a lot longer, and work much more consistently.

It’s covered by the same 7-year warranty on leaks and 3-year warranty on parts as the smaller Stiebel above.


As with our other recommendations, you’ll need professional installation, and a 208/240V hookup.

It’s limited to 4.68 GPM, even in the warmest areas. That’s more than enough for most people, but we know that some people have very large homes with lots of bathrooms, or are shopping for a larger building or a commercial space.

If you have a very high-use household requiring an even larger capacity, you’ll want to look at this Stiebel:

We think it’s overkill for most people, but if you’re trying to heat 3 or more bathrooms at once, or have some larger hot water usage requirement, you may find that it’s worth the extra cost. Be aware that you’ll need a 300A electrical service, though. Most houses with extremely high demand are better off going the gas route, since those models have higher overall output capacities.

A couple of reviews were from buyers who said they’d run into trouble with the chemical composition of their water. However, any issues should be covered under the warranty, and other buyers said that provided you clean the system and follow the manual, there shouldn’t be any issues no matter your water. In any case, Stiebel is very helpful in giving advice based on your own water type.

Top-Rated Natural Gas/Propane Tankless Water Heaters

1. Eccotemp i12

This EccoTemp unit is our top choice for a budget-friendly, low-demand water heater. It’s perfectly suited to entire small homes in warmer areas, and it can reasonably supply a home in a colder area where hot water use is staggered. We think it’s the least you can spend for a tankless gas unit that really gets the job done!

The Specs:

  • Gas requirements: Minimum Inlet Gas Pressure is 4″ w.c (1 Kpa), 3/4” gas line
  • Size: 16” x 16” x 11”
  • Output Capacity: 2-3 GPM max.


It’s very affordable. This one is easily $100 cheaper than our least expensive electric recommendation, and it has relatively low installation costs compared to larger gas models. Assuming you don’t have to make many changes to your current setup, you could reasonably hope to get it up and running for around $500 total.

It performs very reasonably. You can expect to see about 3 GPM output in any area, which is enough for two low-flow fixtures, or a single high-use shower (2.0 GPM+) with a sink running elsewhere. Buyers said it had no trouble getting up to temp, and most said they could easily get away with showering while running a load of laundry. Even reviewers in Northern areas said they could use two fixtures at once without any trouble. Of course, you’ll see better results if you’re using low-flow fixtures and efficient appliances.

It’s 85% efficient. That’s not impressive compared to the 99% electric models we’ve recommended, but in the gas world, that’s pretty great. It’s actually slightly more efficient than our midrange choice, even though it’s a much smaller heater. You can rest assured you’ll see substantial savings on your energy bill!

Previous buyers were very impressed with the EccoTemp’s insulation. They said it barely warmed up at all when it was working, which is reassuring for an indoor gas unit. The vent piping will be quite warm, though, so you’ll want to make sure to insulate that area when you’re planning out your modifications.

It’s nice to look at, as well, which isn’t usually the case with these. If you’re installing it somewhere out of the way, you might not care much how it looks. On the other hand, for folks who want to have it in their living space, the sleek glass exterior and modern appliance look will be a welcome touch!

There’s a child-safety locking feature, which allows you to set an upper temperature limit. It’s designed to prevent accidental scalding.

It’s covered by a 2-year warranty.


Like most gas units, it’s designed to be mounted on an outside wall, with the venting directly next to the unit. Keep that in mind when you’re thinking about where you’d put your new heater.

While it does have the ability to self-regulate when an extra load is placed on the system, it’s not as nimble as more expensive options. So, if you’re in the shower and somebody else turns on hot water elsewhere in the house, there might be a slight drop as the heater compensates. That’s why we think it’s best for single-use/low demand homes.

We’re impressed with the 3 GPM max flow rate for such a small and inexpensive heater. However, it’s just that–relatively small and inexpensive. If you don’t use low-flow and efficient fixtures, and want to use more than one at a time, you might want to look at one of our larger recommendations.

Based on feedback from previous buyers, this seems like a very reliable machine. We could only find one reviewer who had run into problems, and in that case, they’d received a replacement machine. We think this is a safe bet, but EccoTemp is also a relatively new company without a long track record to judge.

2. Takagi

Takagi Indoor Water Heater

This Takagi is an excellent midrange option for small households in cold regions and medium to even larger households in warm spots. It’s rated at twice the capacity of the EccoTemp, and it comes highly recommended by Consumer Reports. We think it’s more than enough for most homes in warm spots, and will do very nicely for whole households which use efficient plumbing fixtures in cooler areas.

Propane version also available:

Takagi Indoor Water Heater

The Specs:

  • Gas requirements: 3/4” line, heater rated at 140,000 BTU
  • Size: 20.25” x 13.75” x 9.5”
  • Output Capacity: 3.3-6.6 GPM max. through 1/2” pipes


It’s highly underrated. By that, we mean that it’s marketed as a very low-use unit, but in reality, for most regions of the US, it’s more than capable of supplying the average home. If you use low-flow fixtures, this can easily supply two showers in the coldest areas in North America. Warmer areas can expect to run as many as three showers, or two showers and a washing machine, for example, assuming each uses less than 2.0 GPM. So, we think it’s really a mid-size water heater instead of a super compact unit.

Even buyers whose incoming water was 36 degrees (the lowest inlet temps in the country) said that they had no problems with showering and still having enough left over for sinks or laundry during the winter.

Reviewers in warmer spots agreed that this was vastly under marketed as a whole home heater. They thought it was plenty capable of supplying the average family home with two bathrooms, and with some water to spare!

Professional testers love the Takagi as well. Consumer Reports scored it very highly, and it’s become a favorite among landlords, contractors, and other professionals who regularly buy and install tankless water heaters.

It’s very well-made. The inside heating system is entirely copper, and there are safety overload switches and sensors galore, to make sure nothing overheats or malfunctions in any other way. Since this one has a better sensor array than the EccoTemp, it’s able to be much more responsive to changes in demand.

It comes with a remote control for added convenience. That definitely beats having to go over to the heater and/or open up the panel whenever you want to make adjustments. Since you can control things from a distance, you can put this somewhere out of the way, where it’s less obtrusive.

It’s covered by a 15-year warranty on the heat exchanger, and a 5-year policy on the rest of the parts. That’s a whole lot more coverage than the EccoTemp, and it rivals most other policies on the market. Takagi heaters also have a very good reputation for reliability.

Lots of reviewers noted that their units had been running for years with no issues at all. Longtime users advised paying close attention to descaling and cleaning the machine out to make sure no problems arose from water composition, which is always a good decision.

It’s rated for ultra-low emissions. This unit meets the Ultra-Low NOx regulations of less than 14 ng/J (<20ppm).


It’s a bit less efficient than the EccoTemp, at 82%. It’s also $200 more expensive than the EccoTemp. You do get twice the capacity, but this is probably going to be twice the price once you factor in installation and modifications to your house.

While we think this is perfectly suitable for a whole home with multiple bathrooms in warmer spots, it’s not good for several bathrooms in cold spots unless you’re using low-flow (1.5 GPM or less) fixtures for your shower and water-saving appliances. If you are, you shouldn’t have any problems. If you use 2.0 GPM or larger fixtures, and you don’t want to have to think about scheduling hot water use, it may be a good idea to go with the larger Rheem below.

You’ll need more substantial ventilation (4” piping instead of 2.5” piping) than you would for the EccoTemp. 4” piping is fairly standard, but the size difference is something to consider as you think about where you’ll install your heater, and what supplies you’ll need to buy.

Some buyers had reliability issues. However, most of the problems seem to have arisen from people not paying attention to descaling or softening their water, or cleaning out the Takagi at the appropriate intervals. Any issues would obviously be covered by the warranty, and Takagi has a great reputation for customer service with customers who have problems, or people just calling to get installation advice.

3. Rheem

Rheem Low NOx Outdoor Tankless Natural Gas Water Heater

Our top quality recommendation for a tankless gas unit comes from Rheem. It’s the only one of our recommendations that’s meant for outdoor use, and it’s the only one that meets Energy Star guidelines for efficiency. This is a big, capable tankless unit that’ll give you as much hot water as you could need, while still saving you energy and space over an old unit! It’s also under $1000.

The Specs:

  • Gas requirements: 3/4” supply, unit rated at 180,000 BTU
  • Size: 21.5” x 19.5” x 8.8”
  • Output Capacity: 4.5-8.4 GPM max.


It has super high output ratings! If you don’t ever want to have to ration your hot water usage or plan to stagger different uses, this is the tankless water heater for you! It can provide at least 8 GPM in warm regions, which is enough for three showers at once–even if you’re using full-flow fixtures! You could easily use this to supply a 2 or 3 bathroom house, with hot water to spare for all the other rooms. Even at the coldest inlet temps, it’ll still crank out 4.5 GPM. For those of us who use low-flow fixtures and water-saving appliances, that’s enough for two showers at once, plus a third usage point.

In any location, we think this provides ample hot water to an average-sized home! It’s the ultimate choice for medium and even large houses across the country. The only people who wouldn’t be more than served by the Rheem would be those in very cold spots with large houses, several bathrooms and very inefficient fixtures (>2.0 GPM). The rest of us will have plenty of supply to go around!

It’s an outdoor water heater. It’s actually the only one of our recommendations that’s designed to be outside, but don’t let that make you think it’s a bad thing! Since it’s already going to be outside your house, this is one of very few gas units that doesn’t need special ventilation built around it. You won’t have to put holes in your wall, buy extra ventilation piping, or any of those typical installation things. Oh, and you won’t even have to make space for it in your house! You can enjoy savings and convenience without taking up so much as a cabinet.

It has even better sensors than the Takagi, which makes it the most responsive of the three. It’s also better at responding to low GPM fixtures, since it’s been designed with them in mind! By contrast, models like the Takagi can take some coaxing to notice a tiny draw and kick on. The Rheem responds instantly, and reviewers complimented how fast and effectively it could make adjustments.

It’s the only one of our gas recommendations that’s Energy Star-rated! This is a real winner for cutting down on your gas bill. Like the Takagi, it’s also rated as low-emission.

It’s made the best of the bunch. This one has an all-copper heat exchanger in the heart, rugged metal housing, and high-grade sensor equipment that’s more than ready to live outside. Buyers said they were instantly reassured when the opened the box that they had bought something that would truly last for years.

Even though it costs close to the $1000 mark on its own, it’s still relatively reasonable to buy. Since there are no installation costs besides mounting and gas hookup, you’ll have to pay your installer a lot less than you would for using one of the indoor units we’ve recommended.

The warranty coverage is generous: 12 years on the heat exchanger, 5 years on parts, and 1 year on labor.


It’s Energy Start compliant, but it’s not the most efficient unit on the market. This is rated at 82% efficiency. It’ll still save you lots of energy, though, and we think it’s the best compromise between efficiency, performance, and value on the gas market right now.

It’s a lot heavier than our other choices. This thing weighs over 50 pounds, all told. You’re going to want to make sure it’s attached to something sturdy, like your wall studs.

It’s an outdoor unit. That’s not necessarily a bad thing, as we mentioned, since you’ll save space inside the house, and avoid venting ordeals. However, it does mean you’ll have to go outside to do any repairs or troubleshooting.

We think this is enough for any typical homeowner, wherever you live. However, we know some people have exceptional needs. If you’re in an extremely cold spot and need more than 4.5 GPM, or a warmer spot with a house that needs more than 8.4 GPM (!), we’ve got you covered with another Takagi recommendation below:

See also:

For small-scale applications:

Just need a tankless water heater for a single room? If you’re trying to supplement your main water heater at home, or setting up a small system in a vacation cabin, this Bosch is a super easy, affordable option! It’s designed for pool houses, attics, basement bars, anywhere you need a small amount of hot water on demand.


Bosch Tronic 3000 T 2.5-Gallon Electric Mini-Tank Water Heater

It’s a “point of use” tankless water heater, meaning it’s designed to be right next to the fixtures it’s going to supply. You can pop it under the sink, or even in the medicine cabinet–it’s really that small. The 2.7 GPM flow rate is enough for most single fixtures, be it a shower or sink, and the best part is that it runs on standard 120V power. It’s the only electric unit in this guide that doesn’t need a special 240V hookup! It’s made just as well as our bigger recommendations, with a glass tank, CFC-free insulation, and a long warranty policy (6 years on the tank, 2 years for other parts).

For big houses:

We’ve based most of our recommendations on small to average houses, or large houses with as many as two bathrooms. If you’re the exception to that rule, and looking to fit a large house with three or more bathrooms, either your own home or a group of apartments, you’ll need something bigger and more high-powered than anything we’ve looked at thus far. Enter this Takagi!


Takagi TH3DV TH3 Series 199000

This beast of a heater is rated to supply between three and four bathrooms, depending on your local climate and inlet temperature. It can crank out up to a whopping 10 GPM! That’s as much hot water as you could possibly want at any given time. It’ll cost a little over $1000, though, and you’ll need to factor in all the installation costs, as it’s an indoor unit. We think this is wildly overkill for most people, but to those who need lots and lots of hot water on demand, this is a rugged, reliable machine that’s up to the task. It’s Energy Star rated, low-emission, lead free, and comes in both propane and natural gas models. Oh, and it’s still less than two square feet in size!


Which of these tankless water heaters should you buy?

Here’s our simplified buying guide!

If you want to use electricity:

EcoSmart: for small homes in cold areas using only one hot water fixture at a time, or up to average homes in warm areas, using up to two fixtures at a time. Our budget recommendation, but not recommended for people who can afford a Stiebel.

Stiebel Eltron DHC E12: a much more reliable choice for relatively low-use homes, supplying up to two low-flow fixtures in warmer areas, or one shower and a sink in extremely cold spots. Our top electric recommendation for smaller applications.

Stiebel Eltron Tempra 24 : the ultimate electric unit for average and larger homes with multiple bathrooms. Our best electric recommendation for anyone who wants to supply two bathrooms at once in cold spots, or two bathrooms and a sink on

If you’re going with gas:

EccoTemp: the best budget-friendly option for alternating/single hot water use in homes in cold spots, or for a small to average homes in warmer spots which don’t use more than a shower and an additional draw, like a sink or washing machine.

Takagi: an excellent midrange option that’s close to the EccoTemp in terms of price, but with twice the output and superior reliability. For entire small homes in cold spots, or medium homes with up to two showers in warmer spots.

Rheem: for average to large homes, with two showers running and extra to spare in warm areas. Our top pick for most homeowners, anywhere in the country, assuming you use relatively efficient plumbing fixtures and appliances (2.0 GPM or less) in extremely cold areas.

How To Shop For The Best Tankless Water Heater To Supply Your Home

Decide on your fuel type

Tankless water heaters come in two main types. There are models which use electricity to heat your water, and models which have a small natural gas or propane burner to generate heat. The type of fuel you end up using will dictate which models you want to look at, so make sure you know up front which you want to use.

Electricity is more efficient than combustion, just like in cars. So, an electric tankless model will use the least energy overall. Electricity is also cheaper in most parts of the country than natural gas or propane. The best part of using an electric model is that you don’t have to think about ventilation! That means you can have your heater pretty much anywhere.

On the other hand, electric models cost more to buy up front, and they cost more per GPM in terms of output. For the same price, you can get about 25%-50% more output for your dollar on a gas unit. You’re also going to need to get a 240V industrial electric hookup installed, and probably some larger breakers, which can cost a few hundred dollars up front.

Gas units are less expensive up front, and by the GPM. Depending on where you live, natural gas or propane may also be cheaper to buy. In terms of the cost of your heater itself, you can supply large homes much more cheaply using a gas model.

On the downside, they have higher installation costs than electric units, since you’re going to have to install ventilation in your walls. That can cost a few hundred dollars for the proper piping and labor, and the ventilation requirement also limits you in terms of where you can place your unit. Oh, and just like an electric unit, most gas lines for these heaters are slightly larger than you’d use for other appliances, so you may need an upgrade to your gas line itself (another expense).

*Within the gas category, there are some models that come configured for either natural gas or propane. We’ve mainly recommended natural gas models, but both Takagi’s come in propane versions as well.*

How do you decide between types of fuel? If you don’t have a strong personal preference, it could come down to cost. Compare electricity and gas costs in your area, and see if there’s a big difference, especially over the long term. If one is significantly cheaper, that might be the way to go.

If you’re thinking about hookups for electricity, bear in mind that you’ll need both a 240V hookup and a certain amperage of service. You may or may not be able to upgrade your amperage, depending on your utility. In the gas department, you could also run into limitations, depending on where you live.

If you’ve compared costs and thought hard, but still can’t figure out which route to go down, just call your plumber and ask their opinion. It never hurts to get an expert’s input! After all, they’ll probably be the ones to install the equipment you buy.

Establish your budget

The tankless water heaters in this guide range in cost from about $300-$1000. When you’re thinking about your budget, the primary deciding factor will be the amount of power you need, in terms of GPM output. The more hot water you want to be able to have at any one time, the more you’ll need to shell out up front!

Aside from the heater itself, you’re also going to be looking at between $300 and $1000 in setup costs for many models. That’ll cover the installation of an industrial 240V power supply, or a larger gas inlet line. It’ll also cover the cost of ventilation for a gas model. Your costs may vary depending on your existing plumbing and heating system, local labor costs, and your building code requirements.

If all of this feels daunting, don’t worry! Tankless water heaters are certainly an expensive purchase, and it can seem overwhelming to think about paying for all the retrofitting. However, rebates and tax credits are available in most parts of the country! Many people find they can cover the entire cost of their heater upgrade through credits and rebates, and pretty much anybody is going to be able to find some savings through that route. Check your local utility, your state’s environmental agency, and through the EPA’s Energy Star program. There are some handy online search engines if you’re not sure where to start searching for programs.

Know your needs

When you’re deciding how large a heater to buy, the primary thing you need to keep in mind is the amount, or supply, of hot water you need. It’s going to be a total flow rate at a given time, such as 4 GPM (gallons per minute). Since tankless models aren’t limited by a set amount in a tank, it’s all about figuring out the maximum rate you’ll want to be able to draw at any given time.

Make sure you judge by gallons per minute, not the size of house! We’ve added some easy descriptions about house sizes to make your comparisons easier, but a single-bathroom house with an inefficient 3 GPM shower head is going to use just as much water as a two-bathroom house that uses water-saving 1.5 GPM shower heads!

So, add up all the GPM rates on the appliances and plumbing fixtures you’d use at a given time. For instance, if you want to be able to take a shower and run laundry at the same time, you’d add your shower head GPM and your washing machine GPM. Always leave yourself at least half a GPM extra for safety’s sake!

Some common hot water draws

  • Shower head (water-saving/low-flow): 1.5 GPM
  • Shower head (standard US): 2.0 GPM
  • Sink faucet (average): 0.5-1.5 GPM
  • Kitchen faucet: 1.0-2.0 GPM
  • Bathtub: up to 4.0 GPM
  • Dishwasher: 1-2 GPM
  • Washing machine (average): 1-2 GPM

Your location also plays a big part in figuring out your GPM requirements. Going from the warmest parts of the country to the coldest, the difference in inlet temperature (where water comes into your house) halves your expected GPM from the same machine! We’ve included both the lowest and highest output ratings for each heater we’ve reviewed. If you’re somewhere in between, or unsure of which climate zone you’re in, all the companies who make the models we’ve recommended have their own helpful maps and sizing charts on either the Amazon listings or their website!

Think about the long term

Like any appliance, your new tankless water heater is an investment. The whole point, aside from on-demand hot water, is to save lots of money on your energy bill, and have the machine pay for itself over time. So, you want it to last for years and years!

In general, we’ve found that the German companies make more durable and reliable tankless water heaters. That’s probably because they’ve been making them longer. It’s also the difference between anything made in Germany versus a Chinese import. You’re looking at better quality, more careful engineering, and all the other factors which make an appliance last longer.

When you’re comparing machines, look for copper heat exchangers and piping on the inside. Copper resists corrosion, and is the most durable type of metal for equipment like this. You’ll also want to check for overload and heat protection sensors, to keep the machine from overheating or blowing a fuse.

Expect a warranty of at least 2-5 years on any unit, and always choose extended and expanded warranty protection when it’s available. We also recommend checking to make sure there are authorized service people near you who can work on your unit if something goes wrong.

While tankless water heaters are vastly more reliable over the long term than tank models, you’ll still find reviewers and previous buyers reporting issues. In the vast majority of cases, they say that it’s something to do with their water composition. Water quality can certainly affect any piece of plumbing equipment adversely, but it should never stop a tankless water heater from running, or seriously affect its performance. To avoid these issues, it’s important to always consider water softeners, descaling, and other procedures according to the manual. Call the company and consult your plumber with questions if you think your water might be an issue–with the right precautions and cleaning routine, it probably won’t be!

What’s Next?

We hope you’ve found your new tankless water heater in this guide! If you think you have, just click on the links in the review to see all the technical specs, and more product details, like flow rate charts from the manufacturer!

Still looking for your perfect fit? Check out one of our extra picks, or click through to Amazon to see more models from the brands we’ve featured here!

If you’re interested in reading more expert reviews and analysis, head to our homepage! You’ll find lots of other helpful guides like this one, all right there!