Best Tankless Water Heaters | My Top 10 Picks

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Moving on from a tank to tankless can go one of two ways:

It can be one of those life-changing decisions that make you wonder how you managed before.

OR it can be a tremendous source of frustration.

I’ve seen both scenarios every day in my work as a plumber.

Water not hot enough or too hot..a “cold water sandwich” becomes a daily occurrence.. the system overloads once a week or more…the air supply gets blocked…ignition failures.

IT CAN BE A MESS if you don’t take the time to choose well.

That’s where I come in

I honestly believe that what you have in front of you is the most well-rounded guide on choosing a good tankless water heater.

If I did my job right here, this 10-minute read should give you all the answers you’ll ever need to choose smartly.

For this guide, I:

  1. Analyzed all the highest rated-heaters tankless water heaters to make a short-list of winners
  2. Gathered data on the short-listed units
  3. Defined and then tweaked a quality-rating system for the heaters
  4. Chose ten best tankless water heaters (which I’ll be presenting in just a moment)

Without much ado, let’s dive right in.

First Things First – Cost Analysis

Note that I’m not saying cost-benefit analysis.

I want to address the elephant in the room – the higher cost of a tankless heater.

Is it worth it?

Let’s do some math.

  1. Let us assume that you get a unit that costs $300-500
  2. Let’s also assume that your current electric bill is $120 (five bucks higher than the national average).
  3. A good tankless unit will likely save you somewhere in the range of $35-45 per month (some outliers can save you up to 60%, but we’re talking averages here)

The conclusion: A good tankless water heater pays for itself within a year or two – that’s the ‘average” case I see in my practice.

Cost aside – it’s hard to put a price tag on having hot water on demand. If I had to use one word for going tankless, I’d go with “liberating.”

Provided that you don’t choose the wrong one. Let’s make sure that doesn’t happen.

For Those In a Hurry- My Top Picks at a Glance

If you’re in a hurry, I’ll get right to the point and present my top two tankless water heaters.

The first is a whole-house solution, and the second is point-of-use.

If you’re looking for a central unit

There’s very little doubt there – my top pick is the industry classic that’s been reigning supreme for years – the Stiebel Eltron.

It’s the proprietary patented continuous flow technology that gives this unit an edge when it comes to the reliability of the hot flow.

To put it simply – I believe this is the only unit that will allow you to forget that you have a tankless heater. With most other models, you’ll be reminded by an occasional change in temperature or a pressure drop.

And that doesn’t mean the units are bad – they’re just not as good as the Stiebel Eltron.

And the numbers confirm it – it’s the one unit that firmly kept the top spot in its category for the whole duration of analysis, maintaining a whopping 90+ % in the user satisfaction category at all times.

If the tankless heater market were a horse race, Stiebel Eltron would be a unicorn -at least in my book.

If you have doubts that I’m somehow favoring Stiebel Eltron, let me put those to rest – I did not receive anything for free from the company, nor do I know anyone there.

I’ve just seen this unit in action.

If you’re looking for a point-of-use heater

The situation here is not as simple. There were a few products that battled it out for the top spot.

In this update, the top-rated point-of-use tankless heater is Ecosmart ECO 11.

The results I’m seeing right now put it shoulder-to-shoulder with two other units that cost more.

It’s as simple as that.

Some products are as good, but there’s no better value for money than the ECO series.

Best Tankless Water Heater Reviews – Top 10

1 – Best Overall - Stiebel Eltron

Stiebel Eltron Tankless Heater – Tempra 12 Plus – Electric, On...
  • CONTINUOUS FLOW – Advanced Flow Control patented...
  • SPACE & ENERGY SAVER – Its small, sleek white design saves...
  • EASY OPERATION – Electronic switch activates the hot water...

When Dr. Theodor Stiebel immersed that first coil in 1924 Berlin, little did he know that a company carrying his name will become a force to be reckoned with in one of the most competitive appliance markets.

My top pick comes from this German brand with a storied history- they’ve been making water heaters for almost a century now.


Size: 4.63 x 16.63 x 14.5 “

Weight: 24 pounds

Power: 12-36 kW

Output water temperature: 86-140 °F

Connections: 3/4″ NPT

Warranty: 7 years for leks and 3 years on parts

Defining features:

  • Continuous Flow technology – patented by Stiebel Eltron and designed to maintain water temperature by adjusting the pressure
  • Space and energy-saving features electronic water flow control and auto-modulation
  • Cleanly designed digital display and intuitive controls
  • The interior heating system is solid copper

What’s better about it?

Let me be clear from the get-go – this is the unit I’d choose for an average American home.

The word “best” has always been too vague for my taste because I work in an industry where things can be measured, tested, and quantified.

The data I have on it overwhelmingly show that it’s every bit as good as heaters that cost 150-250% more.

When I say that this is the “best tankless water heater,” here’s what I mean:

Low number of on-arrival issues and initial flaws

It’s at the very top in that quality aspect. That’s overall, compared to units that cost much more.

Single models that worked for (almost) everyone

There are great units that simply won’t work for your set of circumstances.

Not likely to happen with the Stiebel Eltron Tempra because the power versions range from 12 to 36 kW, with amperage in the range of 50 to 150 A.

Finally, the temperature rise can go from 42 to 62 degrees, depending on the version you chose.

Tempra 36, for example, is a beast and can supply 8 GPM at a temperature rise of 82 degrees F.

It’s the most reliable electric unit I know

Despite being small and silent, its advanced flow control can only be compared to high-end central gas units.

Advanced self-modulation

“Self-modulating” means it adjusts to the amount of water you’re using and turns the heating elements on and off.

Adaptive technology is becoming an industry standard for all the better brands, but, in my experience, Stiebel Eltron got it just right.

And it’s a key factor for me because I know what it means in practice.

To put it simply – going tankless will make you more energy efficient in terms of not using power when you don’t need it. Stiebel Eltron goes one step beyond that – you only use as much power as you need when you need it.

Variable flow ensures a constant temperature

I’m a fan of this feature, and I’m stressing it because not everyone is.

Variable flow means that the unit will restrict flow when you go over the heater’s capacity.

So, you’re taking a shower, and it just happens that your family members turn on multiple appliances to full hot at once. With lower quality units, you’ll feel a change in water temperature.

Not with Stiebel Eltron.

Stiebel Eltron will not just let out cold water – it will lower the flow rate.

In my book, that’s just smart design. The variable flow feature wasn’t there before the company upgraded the Tempra series to Tempra Plus.

I’m glad they did.

I’d rather feel a slight pressure drop once in a blue moon than be hit with cold water during a steamy shower.

If you get the sizing right, it rarely happens, but it’s good to know that the feature is there.

Tempra Plus vs Trend

The differences between the Plus and Trend sub-series of the Tempra are cosmetic and mostly limited to the controls design.

There’s one substantial difference – Tempra Plus features Advanced Flow Control, and Tempra Trend doesn’t.


If you find a Stiebel Eltron Tempra that fits your needs in terms of power and output water temperature, you’re in luck. This is likely where your search ends.


  • Dependable flow and temperature control
  • High energy efficiency
  • Long-term reliability
  • Great customer support with low response times


  • The flow rate vs. temperature rise should be communicated more clearly in their sizing guide

2 – Best Point-of-Use - EcoSmart ECO 11

EcoSmart ECO 11 Electric Tankless Water Heater, 13KW at 240 Volts with...
  • Endless On-Demand Hot Water; Consistent hot water when you...
  • Save Space; EcoSmart tankless electric water heaters are 90%...
  • Save Energy; EcoSmart tankless electric water heaters are...

Saying that Ecormart ECo 11 is the runner-up is not really fair because we’d be comparing apples to oranges – or apples to much smaller apples….anyway, I digress.

The top overall pick (Stiebel Eltron) is a robust central unit. This heater from Ecosmart is a compact eye candy that packs a significant punch.

It dominated the point-of-use category from the moment I started gathering data.

Specs of the ECO 11:

Size: 12 x 8 x 4 inches

Weight: 6.5 pounds

Power: 13 kW

Flow rate: 3 GPM

Output water temperature: 80-140 °F

Connections: 1/2″ NPT

Warranty: lifetime

Defining features:

  • Self-modulating technology patented by EcoSmart
  • Energy-saving focused design (energy factor 0.98)
  • Simple, intuitive controls and a large digital display

What’s better about it?

At no point was another unit close to the ECO 11 in terms of temperature control and efficiency. At least no unit in its price and size range.

Looking at my data now, and you’d have to go two price levels up to get the kind of numbers ECO 11 delivered in our tests. It’s impressive.

The 8 kilowatts and 33 Ampers of “younger brother” (Eco 8) are on the low side for most people, and its “bigger brother” (ECO 18) is much bigger (literally).


Most people looking for a point-of-use tankless water heater will find the Eco 11 to be at the sweet spot between size and performance.

It’s hands-down my #1 choice among the point-of-use (POU) tankless water heaters. If the sizing and the flow don’t seem right for you, there are five other units in the ECO series – from ECO 8 to ECO 36.

Oh, and did I mention that you have a lifetime warranty on this one?


  • Energy-efficient – features advanced self-modulating technology
  • Small, compact design
  • Low incidence of on-arrival issues
  • Low incidence of critical failures


  • In low temperatures, you might see a slight hot water delay (solvable by planning for the heater to be close to the water source)

3 – Rinnai Indoor RL75iN

Rinnai RL75IN, 7.5 GPM, Indoor Installation
  • Energy and Space Efficient: Space-saving design conserves...
  • Optimal Water Pressure: High-performance 7.5 GPM hot water...
  • Instant Heating: Circ-Logic technology enables recirculation...

Specs of this Rinnai:

Type: natural gas

Size: 14 x 9.3 x 23 inches

Weight: 50 pounds

Flow rate: 9.4 GPM

Energy efficiency: 82 %

Output water temperature: 98 – 140 °F (residential), 98°F – 160°F (commercial)

Warranty: heat exchanger 12, 10, and 5 years (residential, combo, and commercial application), 5 years on all other components

Defining features:

  • Energy-star certified
  • State-of-the-art digital controller
  • High-end materials – built for durability & longevity
  • Pairs easily with an external pump

What’s better about it?

There’s one sure-fire way to know that a tankless water heater is top-notch – if it’s not cheap by any means, but no one ever mentions the price except to say it’s worth it.

That’s what I’ve seen in my time installing the R75, and that what I’ve heard from the colleagues I interviewed for this guide.

There’s no point in comparing the efficiency of the gas unit to an electric one. It’s never close, and the latter will outperform every time.

That’s not why people choose gas

They choose it for two main reasons – lower operating costs and higher flow rates (over 8 GPM, which makes them a better choice for larger homes).


Whatever your reasoning is, Rinnai R75 won’t disappoint. I am yet to see (or hear) of someone not loving this heater.

From what I’ve found in my research, people who had a grievance about this unit talked about on-arrival issues. That’s what the warranty is for – 12 years on residential use, 5 on commercial, and 10 if you’re using it for both.


  • Durability and longevity – likely to last twice as long as a classic tank
  • Great value for money
  • Reliable – all Rinnai units are tested before shipping
  • Stable flow rates
  • Modern design
  • Option to minimize the hot-water delay by installing an external pump


  • The product info could be clearer on the residential vs. commercial warranty terms
  • The recirculation function is not built-in, and the cost of adding it to the unit is high

4 – Best for Outdoors - Camplux 10L

Camplux Tankless Water Heater, 2.64 GPM On Demand Instant Hot Water...
  • 2.64 GPM Instant Hot Water -Camplux high capacity 2.64 GPM...
  • 6-IN-1 Multiple Protection- Flame-out protection,...
  • Easy Installation -The propane water heater uses standard...

Specs of this Camplux:

Type: Propane-powered

Size: 12.8 x 5.91 x 20.28 inches

Power: 20W

Weight: 23.8 pounds

Flow rate: 2.64 GPM

Energy efficiency: 88,5%

Warranty: 1 year

Defining features:

  • Compact, space-saving unit – great for cabins and RVs
  • Well-rounded protection – Camplux calls it 6-in-1 (flame-out, anti-freeze, over-heating, air-flow pressure, safe ignition, UL-listed cord)
  • High energy-saving factor
  • Innovative approach to combustion technology
  • Color display

What’s better about it?

For propane-powered units, most gravitas in my research was put on three things – how easy it is to use (and install), value for money, propane-used vs. heat delivered, and the ever-important temperature control.

For this pick, I had to go beyond data-collecting and outside of the plumbing community. I talked to people who are using these – the camping and RV community. Fun, friendly bunch they are.

It turned out that there are a few units close in terms of pretty much all performance aspects except one – the balance between the use of propane and water delivery.


I’ve seen many otherwise great tankless water heaters with higher BTU ratings than people need. The result is going through a propane tank of propane in a few days.

This is the part that Camplux gets just right – it’s also what propelled it to the proverbial king of the hill in this category.

Two thumbs up from campers, RVers, and plumbers.


  • Easy installation
  • Well-designed safety systems
  • Consistent flow rate and minimal hot-water delay
  • Solid value for money
  • Can be used as a portable and/or a wall-mounted unit


  • The tech support could be faster

5 – Best Budget Pick - Ecosmart POU 3.5 & 6

Ecosmart POU 6 Point of Use Electric Tankless Water Heater, 6...
  • Can provide hot water for one sink at 0.5 GPM in warmer...
  • Requires 1 x 30 amp breaker and 10 AWG wire
  • For one sink at 0.5 GPM in colder climates the POU 6 is...


Size: 7 x 11 x 3 “

Weight: 4 pounds

Power: 3.5 or 6 kW

Flow rate: 0.5 GPM for warmer climates for POU 3.5 / 0.5 for colder climate and 1 GMP flow rate in warm climates for POU 6

Output water temperature: 80-140 °F

Connections: 1/2″ NPT

Warranty: 1 year on the exchanger, electronics, and the element

Defining features:

  • Minimal space use – compact under-the-sink design
  • Flow-controlled – it adjusts the temperature based on the flow
  • The flow rate is at the sweet spot for secondary faucets – can handle one gallon of water per minute a temperature rise of 30-35 °F (in warmer climates)

What’s better about this tankless water heater?

Let me get right to what I meant to say in the title above. My inbox is bursting with questions about this type of tankless heater -a small, cheap electric tankless water heater for faucets that are not being constantly used.

That’s why I’m adding this Ecosmart to the list – it’s just powerful enough to allow you to wash your hands after a day in the workshop comfortably.


Out of all the water heaters in this price and capacity range, this Ecosmart heater performed the best in most categories that matter, including energy efficiency, temperature control, and heat exchanger reliability.

It’s also easy to install and won’t make a dent in your wallet. It’s a no-brainer at its current price.


  • Low cost, high value for money
  • Compact design – small for the power it delivers
  • Volume just right for one sink
  • Low incidence of flow rate anomalies
  • Simple operation


  • The customer support could (and should) be faster

6 – Rheem RTEX-13

Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater,...
  • External adjustable digital thermostatic control with LED...
  • Durable Copper immersion two heating elements, field...
  • Simple installation – 1/2 NPT adapters included; side 1/2...

Specs of this Rheem:

Type: electric

Size: 12.63 x 8.25 x 3.63 inches

Power: 13 KW

Flow rate: 3.17 GPM

Energy efficiency: 99.8%

Warranty: 5 years on leaks, 1 year on parts

Defining features:

  • Features two copper heating elements
  • Advanced power control
  • Precise temperature settings – 1 degrees increments
  • Adjustable digital thermostat

What’s better about it?

This small eye candy is one of the most popular units in North America. The predecessor of this model earned the bragging right and the new and improved version (RTEX-13) picks up where the original left off.

To put it simply – it’s a well-rounded product that delivers in all the key performance aspects at a reasonable price.


  • Affordable
  • The smallest unit I know that deserves a mention
  • Easy installation
  • Performance numbers are up there with much more expensive units
  • High GPM for the price
  • Simple, user-friendly controls


  • Not the best choice for bigger homes or cold climate

7 – Noritz NRC66DVNG

Noritz NRC66DVNG Indoor Condensing Direct Tankless Hot Water Heater,...
  • Endless hot water
  • Can be vented with Schedule 40 PVC Pipe and Fitting
  • High Efficiency

Specs of this Noritz:

Type: natural gas

Size: 6.7 x 13.8 x 23.6 inches

Weight: 11.42 lbs

Power: 6.5 KW

Flow rate: 3.17 GPM

Energy efficiency: 99.8%

Warranty: 12 years on the exchanger, 5 years on parts, 1 year on labor

Defining features:

  • Condensing unit makes the most of the energy used
  • Technologically advanced heat exchanger
  • Built-in controller
  • Remote thermostat

What’s better about it?

I’ve said it a few times and I’ll say it again, “the future of tankless water heaters” is in the condensing models. However, most of them are not there yet, meaning that the cost difference is too high to justify the extra energy savings.

That’s not the case with this Noritz. It fully justifies the premium price point by over-delivering in a few key areas, including energy efficiency.


  • Easy to install, thorough instructions
  • The condensing technology allows for the use of PVC venting
  • Highly efficient
  • Quiet
  • Solid temperature control
  • Compact, small footprint


  • You might experience a hot-water delay if the heater isn’t close to the source

8 – RHEEM 9.5 GPM Indoor Direct Vent (condensing)

Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent Tankless Natural Gas...
  • 94-Percent Energy efficient with stainless-steel condensing...
  • Intelligent electronic controls designed to increase energy...
  • Third party efficiency listed by AHRI

Specs of this RHEEM:

Type: natural gas

Size: 18.5 x 9.75 x 27.5 inches

Weight: 79 lbs

Flow rate: 9.5 GPM

Energy efficiency: 94%

Warranty: 10 years limited on the exchanger, 1 year limited on the parts

Defining features:

  • Condensing technology – less power wasted
  • The heat exchanger is stainless steel with an energy factor of 0.94
  • Built-in blower
  • Comprehensive/flexible controls
  • Concise digital display
  • Digital remote
  • Low Nox

What’s better about it?

If you’re looking for a condensing unit, your choices are somewhat limited.

If on top of that, you need a unit that can meet the needs of a larger home, your choice comes down to a handful of tankless heaters.

If this is your scenario, my top pick is this robust Rheem.


  • Highly efficient (condensing)
  • Comes from a reputable brand
  • Great temperature control
  • Easy installation


  • Costs more than similar non-condensing units

9 – SioGreen Infrared Electric Sio14

Sio Green SIO14 v2 Infrared Electric Tankless Water Heater - Instant...

Specs of this SioGreen:

Type: electric, infrared

Size: 25.1 x 17.2 x 9.5 inches

Weight: 28.2 lbs

Flow rate: 2-3 GMP, depends on the temperature rise

Money-back guarantee – 30 days

Defining features:

  • Quartz used as media – no direct contact between water and metals means zero maintenance
  • Innovative infrared technology used to heat the water
  • Auto-modulating smart technology regulates heat delivery

What’s better about it?

The SioGreen is a one-of-a-kind tankless heater but, judging by its success, it won’t be for long. I expect more brands to come up with their own infrared-based models.

The main innovative aspect is the use of Quartz as media and infrared energy.

The result is a highly efficient, user-friendly heater that requires zero maintenance because there’s no mineral buildup.


  • No metallic coils mean low to zero maintenance cost
  • Smooth flow delivery and low incidence of sudden temperature changes (cold water sandwiches)
  • Space-saving compact design
  • Automatic power adjustment
  • Comes with a money-back guarantee


  • Costs more than units in its capacity range

10 – Takagi Condensing 10-Gallon

Takagi T-H3-DV-N Condensing High Efficiency Natural Gas Indoor...
  • Endless hot water, On-demand usage, Compact, Space saving,...
  • Computerized safety features, No pilot light to have to...
  • Safety features include freeze, overheat, surge protection,...

Specs of this Takagi:

Type: natural gas

Size: 10.75 x 17.75 x 22.5 inches

Weight: 59 lbs

Flow rate: 10 GPM

Warranty: 10 years on the exchanger for single-family use and 10 years for commercial use, 5 years on parts

Defining features:

  • No pilot lights mean low to none fire risks
  • Fully computerized safety features (including anti-freeze, overheating, and power surge)
  • High-end materials – the primary heat exchanger is a copper alloy (commercial grade)

What’s better about it?

This condensing Takagi has a unique sales proposal – deliver similar performance values as the competition at a power price point.

What allows it to deliver on that promise is the innovative heat exchanger. It’s made of copper alloy that transfers heat 25 times better than stainless steel – at least that’s what Takagi says.

Judging by the consistently high user satisfaction percentages, Takagi’s claims about this hefty 10-gallon unit are true.


  • Great balance between price and performance
  • Superior temperature control
  • Relatively easy installation
  • Certified for high-altitude areas (up to 10,100 ft.)


  • Occasional report of on-arrival defects

Choosing the Best Tankless Water Heater – Reference Info

Pros and cons of going tankless

The information might be too much to digest at a single sitting, so let’s chunk it down into bite-size pieces – by making a concise PROS & CONS list:

PROS of a tankless heater:

  1. Instantaneous supply of hot water that never runs out
  2. Money and energy savings
  3. Because of the high energy efficiency, they qualify for a 10% tax credit – as of December 2016.
  4. They often qualify for financing programs
  5. Save savers
  6. They last longer than tank
  7. Lower upkeep and maintenance costs
  8. No “stand by loss” of keeping the tank running at all times
  9. Longer warranties
  10. Better suited for smaller homes than accumulating heaters

CONS of tankless heater:

  1. Higher chance of choosing wrong
  2. They cost more
  3. Typically more complicated to install than tanked units
  4. Supply is not unlimited (This might sound counterintuitive because I’ve already said “hot water that never runs out” in the PROS list. “Not unlimited” means that you will see a drop in water temperature if you are running multiple outlets simultaneously. Again, this is only a CON if you don’t choose well – which is not likely to happen since you’re reading this)
  5. Inconsistent water heating – only an issue with the lower quality tankless water heaters

Electric vs Gas

This is one of the first questions you’ll need to answer before choosing.

Here’s my take:

Go with gas if

  • You need flow rates over 8 GMP
  • You have a large family/house
  • You’re looking for a robust central solution
  • You’re prepared to pay more for the reliability and power – both the unit and installation will cost more
  • You’re looking for lower upkeep costs

Go with electricity if

  • Price is a key factor for you
  • You’re working with a smaller installation space (these units are much smaller than gas-powered)
  • Planning the ventilation is complicated in your space (no gas combustion means fewer ventilation concerns and lower installation cost)
  • You’re looking for a high-efficiency rating – energy savings are a crucial factor for you

It’s a zero-sum game

In practice, the last points on the two lists above offset each other. Electric tankless water heaters might be more efficient (98-99% energy efficiency compared to 80-85% of gas), but electricity costs more.

I’d say forget about the upkeep costs and think about the other factors I listed.

One thing is certain – they are both more convenient than a tank water heater.

If you’re interested in getting gas-only then check out these gas water heaters.

Energy efficiency rating & energy factor

You’ll see the two terms thrown around like it’s nobody’s business; make sure you understand what they mean.

The efficiency rating of a tankless water heater is a number that tells you how much hot water is produced by one unit of fuel. That number is also known as Energy Factor (EF).

So, if you see a rating of 0.9, that means that 90% of the energy expended is used to heat the water.

Tankless heaters are much more energy efficient (have a much higher EF) than your standard tank heater.

Flow rate

Flow rate is the number of gallons that your tankless heater can handle in a minute. The numbers you’ll see listed in the specs are based on 25 or 50 degrees Fahrenheit of temperature rise.

It’s one of the critical pieces of information.

For example, in warmer areas, you can heat water just fine with a tankless water heater with a listed flow rate of 4GPM for a temperature rise of 25 degrees. On the other hand, the best tankless water heaters we looked at can handle much heavier loads than that -both in terms of flow rate and temperature rise. And remain energy efficient in the process.

Temperature rise

A number describing the difference between groundwater temperatures and the maximum temperature you can get as an output, at a given capacity.


Warranties vary wildly, but this is what to look for in the best tankless water heaters arena:

With gas units, look for a minimum of:

  • 8 years on the heat exchanger
  • 5 years on all other parts

With electric models look for:

  • At least 5 years on all parts

If you’re not installing it yourself, don’t settle for anything less than a 1-year warranty on the labor.

Tankless water heater maintenance

You’ll see most manufacturers saying that their products require a 6-month or 1-year maintenance schedule.

In practice, the rule of thumb is that the harder your water and the higher your temperature setting, the more often you’ll need to check the unit up. Six months is a good period to shoot for.

My advice here is not to take any chances.

After getting a tankless water heater, gather all the relevant data about your water (hardness, temperature rise, average flow rates), call the manufacturer with the paper in from of you, and ask them what they recommend.

After a few maintenance check-ups, you’ll know if there’s wiggle room to put more time in between. That might void your warranty, though.

Personally, I’m by a by-the-book guy because it leaves me with less to worry about.

FAQs about Tankless Water Heaters

The Basics

What is a tankless water heater?

A tankless water heater (also known as inline, continuous flow, instant-on, instantaneous) is any water heater that delivers on-demand instead of storing heated water in a tank.

How does a tankless water heater work?

They work by heating cold water directly and without storing any of it. It either uses an electric resistance heater with an insulated jacket around them or a gas burner.

What are the benefits of a tankless water heater?

This is a complete list of the most important benefits of a tankless water heater:

  • Energy-efficient – they only heat as much water as you need
  • Convenient – no waiting for an empty tank to heat up
  • Space-saving – great for tight kitchens and small apartments
  • Money-saving – less energy spent on heating up water means lower bills
  • They last longer than traditional units
  • Lower upkeep and maintenance cost
  • Lower incidence of leaks
  • Safer than thank heaters

What are the downsides?

They only have one major downside – the initial cost of both the water heater and installation is higher than traditional heaters.

Who makes the best tankless electric water heater?

According to my database of 104 tested units, these are the top 10 brands of electric water heaters:

  1. Bosch
  2. EcoSmart
  3. Heatworks
  4. Navien
  5. Noritz
  6. Rheem
  7. Rinnai
  8. Stiebel Eltron
  9. Tempra
  10. Trutankless

(alphabetically listed)

What brand of tankless water heater is the most reliable?

In my opinion, these are the most reliable brands of water heaters:

  1. Bosch
  2. EcoSmart
  3. Noritz
  4. Rheem
  5. Stiebel Eltron

I’m stressing that this my opinion and listing these in alphabetical order. It’s because reliability is not one of those quality categories that can draw conclusions based on low data volumes.

What size tankless water heater do I need?

Use these steps to calculate the size of the water heater you need:

#1 – Put pen to paper and calculate your “peak water flow rate

To do this, add the flow rates of the appliance in your home that you typically use. These are reference flow rates:

  • Typical shower head – 2 gallons per minute
  • A water flow rate of older (rain-type) showerheads go up to 5 gallons per minute
  • Water flow rate of a standard dishwasher – 2.5 gallons per minute
  • High-efficiency dishwasher – 0.6-1.5 gallons per minute
  • Faucet has an average water flow rate of 1 gallons per minute
  • Standard washing machine – 2.5 gallons per minute
  • A high-efficiency washing machine has a water flow rate of 1 gallons per minute

#2 – Find the groundwater temperature in your area – use the groundwater temperature map to do that.

#3 – Calculate the difference between the groundwater temperature and the temperature you’d like to see on your faucets – this number is also known as “temperature rise” (ΔT for those who remember high school and professionals)

In my experience, people typically go for the range of 110° F – 120° F for their faucets.

#4 – You now have two pieces of information to choose the right size of tankless water heater for you – the temperature rise and the peak flow.

Remote control

The better tankless heaters typically come with a remote control. That usually means a higher price tag on the tankless heater.

How to install a tankless water heater

If you aren’t experienced with appliances, installing tankless heaters might be best left to professionals – if we’re talking about a central water heater.

A point-of-use water heater is pretty easy to install.

To install a tankless heater, follow these steps:

  1. Remove the old tank by first shutting off the water and gas that leads to the hot water tank
  2. If you’re working with gas, you’ll need a line that will lead from the water heater to the gas meter
  3. You’ll also need to drill a hole on the side of the house that is convenient to you and still close to the heater
  4. Fresh air intake will go through the PVC pipes you’ll insert into the hole (step 3)
  5. Connect the cold water lines to the tankless hot water heater and draw lines out of it. I suggest using copper pipes here for energy efficiency.
  6. You can install a crossover valve at the furthest plumbing fixture for optimal flow rate, which helps even with the best tankless water heaters.
  7. Turn all parts of the system on and test

Going into greater detail here is beyond the scope of this guide. I have a dedicated piece in the works that will cover all types of tankless heaters.

Cost of tankless water heater

The total cost of a tankless water heater will be the range of $100-3,000.

That might seem like a vague cost description, but the costs will vary depending on the type of tankless hot water heater you choose and how easy the unit is to install. A point-of-use heater that’s easy to install will cost much less than a central water heater -both initially and in the installation cost.

Some factors that will affect the initial cost of tankless water heaters:

  • Energy factor (energy efficiency, efficiency rating)
  • Temperature rise and flow rate (gallons per minute)
  • What type of heat exchanger the tankless unit comes with. In layman’s terms, a heat exchanger is any device that transfers heat from one source to another; they’re not exclusive to a water heater.
  • If it includes self-modulating technology
  • Whether it’s a mini tank, point of use, or central
  • Warranty terms – the best tankless water heaters come with a lifetime warranty. To be honest, the warranty is only a factor if the

Other Relevant Questions

Where is a tankless water heater installed?

Ideally, you’ll install your water heater somewhere inside the house. It is possible to install a tankless hot water heater outside the house but take precautions to avoid direct rain and sunlight.

With a central water heater, the ideal location would be a well-ventilated basement or pantry, while point-of-use and mini-tank models will find a cozy nest under the sink or in a cupboard.

What size tankless water heater to replace a 50-gallon tank heater?

To replace a 50-gallon tank heater, you’ll need a robust 10 GPM gas unit or 25+ kW of power in an electric tankless water heater – for the colder climates.

A 7-8 GP gas unit (or 17-18 kW electric) will do the trick of replacing a 50-gallon tank water heater for warmer climates.

Other factors, like self-modulating technology, can contribute to the size of a tankless unit that will successfully replace a 50-gallon tank.

Will a tankless water heater work without electricity?

No, they won’t.

That goes for the central gas units, too – their control panel is powered by electricity.

Will tankless water heaters freeze?

The answer is, “Yes, tankless water heaters can freeze despite the freeze protection that the better ones come with.”

The freeze protection will work temporarily in the ranges of -5 to -20 degrees Fahrenheit. That means winterizing is a good idea in colder climates.

If the water heater is inside, there are simple things you can do to prevent freezing, like insulating the external pipes or installing pipe-heating cables.

If it does happen, don’t operate a frozen tankless water heater under any circumstances. You’ll cause permanent damage, and most manufacturers won’t cover damages caused by freezing.

If it does freeze, will it thaw on its own?

Yes, a tankless water heater will thaw on its own as the temperature rises.

Will they save you money?

Yes, they will – you can expect the good tankless water heater to save you 25-35 %of your electric bill.

How likely are they to leak?

What is BTU?

A BTU is the measurement of heat energy required to raise one pound of water in temperature by a single degree Fahrenheit.

Takeaways and Updates

I do my best to stay on top of things in the industry and update this guide with new data every two months.

If I see a significant shift in the Top 10 (like a change in manufacturing practices), I do an unscheduled update to reflect what’s going on.

What this means for you

It means that the guide you have before you is THE single most -complete reference piece on choosing a tankless heater out there. It also means that the data you see here is always fresh.

Finally, it means that, even if you don’t decide to buy anything today, it’s only smart to bookmark this and get back whenever you need to.

Yours in conservative buying choices,

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