10 Best Tankless Water Heater Picks of 2020 | Reviews

Find the best tankless water heater for your home with our ultimate buyer’s guide and top 10 tankless water heater reviews. We’ve got everything you need to know right here!

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Let us help you find the best tankless water heater for your home. Our tankless water heater reviews will show the way.

We’ve included all the key facts about the top models in the table below. Following the table, we review each product in a bit more detail.

These are the top-rated water heaters available. They come in a range of price brackets, but all have great reputations. We’ve included both the best electric tankless water heater reviews and the best tankless gas water heater models as well.

Check out our buyer’s guide to see what key features you should be looking for in a tankless water heater.

We’ll start with the comparison table and reviews. Alternatively, jump to the Introduction to Heaters & Buyer’s Guide presented below.

Stiebel Eltron Tempra 24 Plus


4.7$$$5.4ElectricReliable, great temperature controls, consistent hot water flowThree year warranty is less than other models
Rinnai RUC98iN Ultra Series


4.6$$$$$9.8GasHigh energy efficiency rating, huge water flow rate, 12 year warranty on heat exchangerMore expensive than most
Takagi T-KJr2-IN-NG


4.6$$$6.6GasHigh water flow rate, turns itself off if overheating, 10 year warranty on heat exchangerVenting required


4.3$$$$$9.5GasHigh energy efficiency, quality components, massive flow rateOne of the more expensive tankless system we’ve reviewed
EcoSmart ECO 27


4.3$$6.0ElectricWorks well in colder climates, energy efficient, digital controls, limited lifetime warrantyWater flow rate lower than some competitors
Rinnai RL75iN4.3$$$$$7.5GasOffers a large temperature range, can be converted from gas to propaneMust use the listed vent
EcoSmart ECO 114.1$2.0ElectricDigital controller gives complete control, limited lifetime warrantyOnly suitable for smaller homes
Eccotemp L10



4.0$2.65GasAuto shut-off, portable, great priceLimited flow rate, only suitable for small homes & RVs
Eccotemp FVI-12-LP


3.9$$3.4GasLow energy consumption, perfect for smaller homesWouldn’t suit homes with more than one bathroom
Rheem RTEX-13


3.7$4.0ElectricGreat value, reliableNo digital display

Before we present you with our best tankless water heaters reviews, we want to tell you that GPM stands for gallons per minute. This is a measure of how much hot water can be provided every minute. Larger families will need larger numbers.

Next, you can read our more detailed tankless hot water heater reviews. We give our recommendations for the best gas tankless water heater systems and the best tankless electric water heaters.

1. Stiebel Eltron Tempra 24 Plus Electric – BEST ELECTRIC TANKLESS WATER HEATER – OUR PICK

The first of our tankless water heater reviews is for the Stiebel Eltron Tempra, an electric tankless water heater that comes with really impressive customer feedback. It is considered one of the most technologically advanced systems on the market today.

It features Advanced Flow Control (a feature exclusive to this heater) which ensures that there is always a constant flow of hot water, no matter how big the household water demands are. This model doesn’t have the problem with temperature fluctuations like some others do.

The Tempra features a maximum water flow rate of 5.4 gallons per minute (GPM). This makes it able to handle the hot water needs of medium to large households. It can handle the demands of homes with two bathrooms. The temperature is controlled accurately with the help of digital temperature control.

This means you can be very precise (down to the degree), and not waste any energy heating the water to unnecessarily high temperatures. It’s German-engineered, and just like their cars, it’s a great piece of design.

The Tempra has been given a recent redesign to improve on an already impressive machine. The new improvements include:

  • Upgraded electronics
  • Flow sensor design
  • Hinged cover (for easy access)
  • Advanced Flow Control system

Since it is an electric heater it doesn’t require any outside venting. This makes installation much easier than a gas model. You must make sure that you have the power capabilities at home to handle a water heater though.

It features a slim, sleek design and will take up very little space. It measures 16 5/8 (width), 14 ½ (height), 4 5/8 (depth). If you are moving from a traditional tank-based water heater to this, then you are definitely going to have some extra space at home to fill.

Stiebel estimates that you can save between 15-20% on your hot water bill each month compared to a conventional hot water heater.

Key Features

  • Rating: 4.7
  • Price: $$$
  • Electric tankless water heater rated for 240 V @ 24 kW
  • 5.4 gallons per minute of water flow
  • 3 Year warranty
  • Advanced Flow Control technology
  • Digital temperature controls
  • Slimline design
  • Robust and dependable

Bottom Line

This heater has combines some amazing technology and reliability into a tempting sleek unit. It’s a system of really high quality, and a recent price drop makes it amazing value on Amazon now too. This is one of the best electric tankless water heaters out there.


This model from Rinnai is a gas-powered heater. It features the highest energy efficiency rating we have seen. It has a thermal efficiency of 95% and an Energy Star certificate. It also has an Energy Factor rating of up to 0.96. This is among the highest ratings available in a home water heater. This means it is able to run more efficiently than most heaters, saving energy and money in the process.

This model has an expensive initial cost, but you can expect energy bills to fall due to its efficient operation. It also has a staggering max water flow rate of 9.8 GPM. This means it is able to service even the largest of households. Even homes with 4 or 5 bathrooms won’t have any problems with this model.

In fact, Rinnai says it is able to handle 4 showers running simultaneously. This water heater will never be in any danger of a drop in pressure. Even when running at full capacity, it will do so quietly. This is said to be one of the quietest tankless water heaters on the market.

As it is a gas-powered system is does require outdoor venting. Rinnai is the only manufacturer to offer two venting options on installation. The unit ships with both concentric and twin pipe PVC venting included. This gives more freedom at installation time.

Being one of the more expensive models, it also comes with a solid warranty. You get 12 years on the heat exchanger and 5 years on the parts. Aside from the EcoSmart models, this is the best warranty we have seen. If you want a more in-depth analysis of how this product works, check out our complete Rinnai RUC 98 iN tankless water heater review!

 Key Features

  • Rating: 4.6
  • Price: $$$$$
  • Energy Star certificate
  • Amazing energy efficiency
  • 9.6 gallons per minute water flow rate
  • Min/max BTUs: 15,200-199,000
  • Really low NOx emissions
  • Warranty: 5 years parts, 12 years heat exchanger

Bottom Line

Though initially more expensive, this model will save you more in the long run due to its exceptionally efficient operation. This model tops our tankless gas water heater reviews and is a system of real quality. Rinnai is probably the best tankless water heater brand in the business.

3. Takagi T-KJr2-IN-NG Gas Tankless Water Heater – GREAT EFFICIENCY & VALUE

takagi tankless water heater

Despite having one of the most unimaginative names in the whole house tankless water heater world, the Takagi T-KJr2-IN-NG tankless water heater is actually a heater of some pedigree. It is attractively priced for a unit that packs so many impressive features.

It is a gas water heater. This means that is slightly more efficient than an electric unit, but it will require external venting to allow the gases to escape. The unit needs 4-inch category III stainless steel venting.

It comes with an Energy Star certificate. This means it has been recognized as being one of the more energy-efficient models on the market. It boasts an energy factor of 0.81-0.83. Now, this isn’t quite as efficient as the Rinnai model we just talked about, but be aware that this unit from Takagi costs less than 1/2 of the price. It packs quite a punch for something so well priced.

An impressive feature of this water heater is its ability to monitor the input and output water temperatures to maintain a steady temperature. This means there are no temperature fluctuations when you are having that relaxing shower.

This model from Takagi gives an impressive water flow rate of 6.6 gallons per minute. This makes it suitable for even large homes. Homes with 2 bathrooms can be supplied with enough water for two showers to run simultaneously quite easily.

Key Features

  • Rating: 4.6
  • Price: $$$
  • Gas-powered tankless water heater
  • 6.6 gallons per minute maximum water flow rate
  • Energy Star certificate
  • Great value
  • Warranty: 5 years on parts, 10 years on heat exchanger
  • 140,000 BTU

Bottom Line

This is impressively priced for something with Energy Star certification. A great option that doesn’t have to break the bank. It’s got most of the perks of the more expensive units but lacks the price tag. This tankless hot water heater reviews really well.

4. EcoSmart ECO 27 Electric Tankless Water Heater – TOP BUDGET CHOICE

eco smart best electric tankless water heater

The ECO 27 electric tankless water heater is our budget choice, but don’t be deceived into thinking that this isn’t an impressive water heater, because it is. It’s attractively priced and boasts an array of impressive features that should make it a worthy consideration for any prospective buyer.

An awesome feature of this heater is its ability to function even in the colder of climates. Tankless water heaters don’t like really cold water, but this model will work with water as cold as 37°F. Now you won’t reach the peak performance level of 6 gallons of water a minute at this temperature, but it will cope better than others. EcoSmart says that the peak water flow rate of 6 GPM is capable of handling the hot water demands of 4 showers running simultaneously.

It features a digital temperature control which allows you to adjust the heat to the nearest degree. By controlling the temperature so precisely you can save energy, and adjust the settings according to the time of the year. The temperature can be adjusted between 80°F – 140°F. This is one of the least expensive models to offer digital controls like this. Another great feature is its advanced self-modulating technology. This lets the ECO 27 adjust how much energy is needed according to how much hot water is needed.

For me, the most amazing thing about this model is the lifetime warranty. This is unique in the heaters that I have reviewed and is made even more impressive a fact when you consider the price of the unit. This is the best electric tankless water heater when it comes to value for money.

The unit is slim and attractive. It measures just 17x 17x 3.8 inches. It is made up of high-quality copper and stainless steel components that are durable, efficient, and easily replaced. If you want a more detailed guide on this product, check out our EcoSmart ECO 27 heater review!

Key Features

  • Rating: 4.3
  • Price: $$
  • Electric powered tankless water heater
  • Rated for 240V and 27kW
  • 6 gallons per minute maximum water flow rate
  • Will operate in colder climates
  • Digital temperature controls
  • Advanced self modulating technology
  • Lifetime Warranty

Bottom Line

Our budget choice due to the array of features and amazing warranty it offers. If you live in a colder part of the country, then this whole house tankless water heater is definitely worth a close look. This whole house electric tankless water heater reviews really well on websites like Amazon too. Due to the outstanding value it offers, this is one of the best hot water heaters available.

5. Rheem RTG-95DVLN Natural Gas Tankless Water Heater – A SYSTEM OF THE HIGHEST QUALITY

Rheem RTG-95DVLN Natural Gas Tankless Water Heater

The Rheem RTG-95DVLN comes out on top in our gas tankless water heater reviews. It’s one of the more expensive models we’ve encountered, but it backs up the price tag with some impressive stats. It packs a whopping 94% energy efficiency! If you are serious about reducing energy bills, and also your impact on the environment, then this is water heater isn’t one to be missed.

Besides high efficiency, it also offers a large capacity. It will happily output up to 9.5 GPM of hot water in your home. This is among the largest capacities available in a domestic heater of this type. It is more than capable of looking after the hot water demands of a really big family home with multiple bathrooms.

It features electronic controls and a digital display that allow complete control over the settings. It is even able to self-diagnose any issues, which makes maintenance really simple and straightforward. The electronics are designed to increase energy efficiency and safety. The individual components are tested by third parties to ensure the highest of build qualities.

This Rheem heater has an exclusive water savings setting. This is designed to save up to 1,100 gallons of water per year by reducing the flow of water until the temperature reaches the threshold set on the unit.

Another awesome feature is the introduction of a minimum water flow rate and activation point. This means the home will receive hot water even in times of low demand. Some tankless heaters struggle to output enough hot water unless the water demand reaches a certain level. No such problems with this model.

As it runs on gas it requires external venting. It can accommodate up to 38 feet of 3-inch pipe or up to 5 feet of 2 inch PVC pipe. The unit is designed to emit lower levels of NOx.

Key Features

  • Rating: 4.3
  • Price: $$$$$
  • Gas-powered tankless water heater
  • 9.5 gallons per minute water flow rate
  • Smart electronics
  • Up to 94% system efficiency
  • Digital controls
  • Hot water even in low demand situations
  • 5 Year warranty

Bottom Line

Hard to match efficiency and features. It doesn’t come cheap, but you can be assured of its quality and efficiency. This tankless gas water heater reviews really well from anyone that uses it.

6. Rheem RTEX 13 Electric Residential Tankless Water – AMAZING VALUE

Rheem RTEX 13 Electric Residential Tankless Water Heater

This Rheem RTEX 13 tankless water heater reviews really well, and it is also the cheapest we have featured. It is the most popular hot water heater on Amazon, and has hundreds of favorable reviews. It is electrically operated and fits standard 1/2 inch fittings.

A max water flow rate of 4 GPM isn’t huge, but it can easily handle small to medium homes.  It doesn’t have the delicate digital controls of other models but comes at a fraction of the price. This is a unit that is unspectacular in its design, but has shown to be a consistent and reliable performer, time and time again. It comes highly recommended on Amazon by many happy customers.

Key Features

  • Rating: 4.2
  • Price: $$$
  • Electricity-powered tankless water heater
  • 4 gallons per minute water flow rate
  • External adjustable digital thermostatic control with LED display
  • Self-modulating power control
  • 99.8% energy efficient
  • Water-Saver Shower Head – 1.5 GPM
  • Simple installation – 1/2 NPT adapters included; side 1/2 inch Compression water connections
  • 6 Year warranty

Bottom Line

This model is cheap (relatively speaking) and it doesn’t show off. It’s a dependable water heater, that is perfect for medium to small homes and even holiday homes. The warranty and the inherent endurance of this unit make it one of the best choices in tankless water heaters on the market today.

7. Rinnai RL75iN Gas Tankless Water Heater – TRUSTED PERFORMER

Rinnai RL75iN Gas Tankless Water Heater

This is the second of the Rinnai tankless water heater reviews we have featured. The RL75iN is a gas-operated system that is suitable for homes with 2-3 bedrooms. It offers a max water flow rate of 7.5 GPM, which is quite substantial.

It comes with a really good 12-year warranty on the heat exchanger (5 years on parts). It is Energy Star certified which means it offers really good energy efficiency.

It is controlled digitally so the user can have complete control over temperature settings to the nearest degree. This has the benefit of saving energy, as you can be very precise with how hot you need your water. Being a gas system it will require ventilation. This Rinnai tankless water heater has a great reputation, and the brand is held in high regard.

Key Features

  • Rating: 4.3
  • Price: $$$
  • Gas-powered tankless water heater, indoor-only installation
  • 7.5 gallons per minute water flow rate
  • Control-R 2.0 mobile app features timers and scheduling options for distance control
  • Energy Factor of .82 for both gas types
  • Leak detection shuts off water to the unit to limit property damage
  • Enhanced scale detection lessens the possibility of serious damages
  • Temperature range with controllers: 98ºF – 140ºF
  • Warranty: Residential Factory Warranty – 120 months (heat exchanger), 12 months (labor), 60 months (parts).

Bottom Line

A trusted brand that offers exceptional performance. The Energy Star certificate proves how capable it is of efficiently heating water in your home. This unit has few competitors, if any when it comes to best tankless gas water heater models considering its tech specs, features, excellent customer reviews, great warranty, and overall brand reputation!

8. Eccotemp FVI-12-LP Gas Water Heater – GREAT VALUE

Eccotemp FVI-12-LP Gas Water Heater

This Eccotemp FVI-12-LP water heater model runs on propane which is a more efficient power source than the electric-powered models. It has a digital display system and has independent controls for water and gas. It has a maximum water flow rate of 4 GPM which would suit smaller homes best.

The 2-year warranty is a bit less than what competitors are offering, but this system is one of the cheaper water heaters available. It doesn’t consume as much energy as other models but doesn’t heat water to such a high temperature.

Key Features

  • Rating: 4
  • Price: $$$
  • Whole-home indoor gas-powered tankless water heater
  • Uses liquid propane
  • 4 gallons per minute water flow rate
  • Activates only on-demand with no pilot light necessary
  • Fully automatic temperature controls with an energy-saving mode and child lock technology
  • Safe electronic ignition system
  • Requires a standard 110v electrical outlet with UL-listed cord
  • Easy installation: standard 1/2″ NPT water fittings and comes with horizontal venting
  • Sleek, modern design with black tempered glass front panel featuring an easy to use LED display controls
  • Warranty: 2 years

Bottom Line

This is a great choice for smaller homes. It doesn’t use as much gas as other similar tankless gas water heaters and does a great job in the right circumstances. The unit pulls about 2 watts idle and 1.07 Amps during operation, so you don’t have to worry about energy consumption. It is the perfect choice for vacation cabins, cottages, and smaller homes/apartments.

9. Eccotemp L10 Outdoor Water Heater – BEST RV Tankless Water Heater

Eccotemp L10 Outdoor Water Heater

This Eccotemp L10 portable tankless water heater is slightly different from the other model we already discussed. It is portable and can be installed outdoors. Due to its smaller size, it also has a lower water flow rate of 3 GPM. It comes with standard 1/2 inch fittings so can be installed easily. It also has an automatic safety shut-off to prevent accidents.

This Eccotemp model is competitively priced and is one of the cheaper units we have looked at. It’s a great fit for RVs, vacation homes, and campers. It wouldn’t be able to be heavily used but would work well under the right circumstances.

Key Features

  • Rating: 4
  • Price: $$$
  • Portable gas tankless water heater
  • Uses liquid propane
  • Comes with CSA regulator for use with standard 20 lb. grill propane tank
  • 3 gallons per minute water flow rate
  • 2.6 gallons per minute of water consumption
  • Range of temperatures between 50 to 140 degrees Fahrenheit
  • Electronic ignition powered by 2 “D” cell batteries
  • Compatible with 12-volt water pumps
  • Includes: gas regulator and hose, showerhead, garden hose adapter, & output water quick connect
  • Operating range of 20-80 psi
  • Warranty: 1 year

Bottom Line

This is the perfect RV tankless water heater. It’s well designed for the demands of traveling. It is also the ideal choice for campsites, cabins, or simply around the house. It also works great if you live in a secluded area and you still want hot water even if electricity is not readily available.

10. EcoSmart ECO11 Electric – BEST FOR COLD CLIMATES

EcoSmart ECO 11 Electric Tankless Water Heater

This whole house electric tankless water heater from EcoSmart, the ECO 11 electric tankless water heater has an intuitive digital interface, giving the user complete control over hot water operations. Being from EcoSmart it also has the advantage of having a lifetime warranty. This is an amazing feature, which makes EcoSmart models unique.

This model is suited for smaller homes and has a relatively low water output rate of 2 GPM. If you have more than one bathroom then, you should take a look at the larger EcoSmart ECO 27 which we discussed a bit further up the page. Likewise, if you live in a place with a colder climate, the ECO 27 would be a good fit. In smaller homes, this heater can do a really efficient job. It has an attractive price tag too.

Key Features

  • Rating: 4.2
  • Price: $$$
  • Electric tankless water heater
  • Patented Self Modulating Technology and design
  • Saves up to 60% on your water heating costs
  • 99.8% energy efficient
  • Uniform Energy Factor: 0.98
  • 2 gallons per minute water flow rate
  • Best for climates where the incoming water temperature is 67°F and above
  • Digital Temperature Control in 1-degree increments
  • Plumbing connections are 1/2″ compression fitting with the option of 1/2″ NPT adapter included
  • Warranty: lifetime

Bottom Line

This is one of the few heaters that will work well with colder input water. A lifetime warranty isn’t to be taken lightly either. This last model on our list of best tankless water heaters is a dream came true for a small apartment or any small point of use application. If you did not figure this one out yet, you can use this heater for multiple or single applications depending on your climate. In warm climates, the ECO 11 can handle two sinks running simultaneously and one shower, or two sinks simultaneously in colder climates.

Best Tankless Water Heater Reviews: A Buyer’s Guide

Tankless or ‘on-demand’ water heaters are a more energy-efficient solution to the problems posed by old-fashioned storage tank heaters. The water heaters of the past were ideal in their day, but in modern times we need a more practical solution.

Rather than store heated water in a giant tank, tankless heaters heat the water as and when you need it. This ‘on demand’ function makes them more energy efficient and means you can save money on your energy bills each month.

One of the main categories you will see mentioned about these units is the maximum water flow rate. This number should be one of your key considerations when browsing on-demand heaters. Measured in gallons per minute (GPM), this is the amount of hot water that will be available to your household at a particular time. The top models will give as much as 10 GPM, which will be enough for even the biggest of families. If you want to learn more about these measurements, check out our guides on how water filters work!

Tankless water heaters were first readily available around 10 years ago. However, in their infancy, they were unreliable as the technology wasn’t quite ready for them. These days technology has turned them into machines of efficiency and they have improved in every area.

Improvements in Modern Day Tankless Water Heaters

  • Modern-day water heaters retail at much less intimidating prices than those of 10 years ago.
  • They are easier to install, as they have more practical designs which makes connecting to existing gas lines much more straightforward.
  • There are no longer problems with inconsistent water temperatures. Manufacturers have solved this problem in innovative ways by introducing buffer tanks and recirculation pumps.
  • They are more reliable and much easier to maintain.

How Do Tankless Water Heaters Work?

Gas and electric tankless water heaters work in the same way as standard water heaters that have tanks. The difference is that they are on-demand water heaters, or a point-of-use water heater. A point-of-use water heater is able to heat the water much more quickly and is able to work only when needed. This means it doesn’t don’t need a storage tank and doesn’t use up the energy needed during standby operation.

When a hot water tap or appliance that draws hot water is turned on in the home, cold water is drawn into the water heater. The unit senses the flow of cold water and activates the burner. This then warms the heat exchanger (the part that heats the cold water). The heat exchanger is surrounded by the incoming cold water, which is then heated to the desired temperature, ready to travel on to the desired location. Since these heating units only heat water as it is required, a demand water heater is much more efficient than a conventional water heater.

Some Energy Star certified tankless hot water heaters use a further heat exchanger. This allows them to use 9 % less energy than regular units. The second exchanger takes heat from the hot combustion gas and condenses (cools) it. This means that the exhausted gas is much cooler than regular systems. Generally speaking, if the exhaust gases are cooler then it means the system has been more efficient and less energy has been wasted.

Before You Buy: Checklist

1. Estimate the capacity that you’ll need

This is really important with a tankless system. If you choose a model that can’t keep up with demand, then you won’t get any hot water.

While capacities of storage water heaters are defined as the number of gallons that fit into the tank, whole house tankless water heaters are measured in a different way. So how is the capacity of a water heater measured? Well, tankless hot water heaters are defined by the amount of hot water they produce in one minute. This gallons-per-minute (GPM) rating can vary from about 2-13 through different manufacturers. To estimate the type of capacity that you will need, you should imagine peak water usage times in the home. Here are some average numbers to help you estimate your peak water usage:

Reason For UseGallons per Minute (GPM)
Clothes Washer3.3
Shower and Bathtub2.5
Kitchen and Bathroom Sink2.2

If for example, you have two bathrooms and there are times when people will be showering simultaneously, then a model with a GPM rating of at least 4 would be desirable. However, a one bedroom home could suffice with something as low as 3 GPM. These GPM ratings also depend on the temperature of the incoming water. If you live in a cold area then expect the stated GPM value to be lower.

This isn’t the only number that you should be checking though. Each model has its own sizing chart. This includes information about the flow rate, the number of hot water fixtures in a home, and the effect of temperature rise. The sizing chart displays how a water heater performs in each situation so that you can make sure you get the right-sized model for your home.

Check out the sizing chart for the Stiebel Eltron Tempra range here.

2. Check out the warranty

The longer warranty models will probably be more expensive, but for something that is going to get used as much as this, it might well be worth it. Warranties can run for over 10 years with some models. Be aware that most of the warranties depend on the unit being installed by a professional. The best tankless water heaters come with solid warranties.

3. Think about where you will install it

A point-of-use water heater (or “demand water heater”) is usually very small and compact. However, some will need to be installed near a gas supply, and some models will need ventilation for combustion gases. Changing to a tankless system from one that uses a tank will free up some valuable space anyway.

4. Make sure your home is a good fit for a tankless heater

If your current water heater is electric and you don’t have the capability to provide propane or gas, then you probably shouldn’t go for a tankless system. You would need to increase the capacity of your electrical system by too much for a tankless electric water heater to be worthwhile.

Also, these types of heater don’t fit extremely cold water supplies. The heater’s capacity depends on the incoming water temperature. The colder your water the less GPM of hot water you will get. This is because it has to heat the water more and for longer because it’s cold. Choose your tankless water heater based on the winter water temperature in your area. This caters for the worst case scenario. The output will be much better through the other three seasons.

Why Get A Tankless Water Heater Instead of A Regular One?

They have many benefits over standard water heaters. Let’s have a look at why they are a better fit for your home.

  • They are more energy-efficient. They only heat water when it is needed.
  • Water heaters are said to account for around 25% of all energy consumed in a household. Improving the energy efficiency of this unit will make a big difference in energy consumption.
  • They are cheaper to run because of this.
  • They won’t run out of water. A standard water heater only has as much hot water as is inside the tank.
  • They take up less space. A residential tankless heater is only around the size of a small suitcase.

Tankless Water Heater Pros and Cons

Let’s discuss the pros and cons of tankless water heaters now that you know more about these products!


More energy efficient

As these systems don’t have to maintain the water at a constant temperature, they use less energy. They work on an ‘on-demand’ basis. This means they use just the right amount of energy to heat the amount of cold water that is needed. Energy is not wasted keeping a tank of cold water hot. They also provide a more consistent temperature of the water, meaning that scalding hot water doesn’t come out of the faucet. This again saves energy. The best tankless hot water heaters are incredibly efficient machines.

Cheaper to run

A by-product of being more energy efficient is that they will save you money on your energy bills too. Water heaters can account for around 25% of energy bills, so significant monthly savings can be made.


Traditional water heaters with tanks can be huge. The best tankless water heater units don’t have a tank so they require very little space. Even the larger units are only around the size of a medium suitcase.

Won’t run out of hot water

These units heat the water as and when it is needed. This means they are not limited by the size of a hot water tank. As long as you have a model that has a heating potential and water flow rate big enough to keep up with demand, then you won’t run out of hot water.


Not great in cold weather

If your incoming water is likely to get seriously cold, then maybe a tankless system isn’t a good fit. This would require a lot of energy to get the cold water hot and would slow down the hot water flow rate. You could get around this problem by getting a system with a really large flow rate.

High start-up costs

These systems are generally more expensive than their traditional counterparts. They may also require some extra work upon installation if you need to upgrade existing gas (propane or natural gas) or electrical infrastructure (natural gas vs propane is an additional consideration). But in the long run, you are likely to save money and you will recoup this cost.

Not a good fit for really large households

I’m talking +4 bathrooms in size. This would push the limits of the high capacity systems, and might even need multiple systems to cope.

How Do I Maintain a Tankless Water Heater?

These devices contain a heating exchanger (heating coil) which is surrounded by water when it is in operation. Water contains minerals like calcium and magnesium which create limescale that binds to the heating element and walls.

As the heater gets very hot very quickly it will “bake” the minerals to the inside of the unit. This limescale will reduce the efficiency of your water heater and can even break it. Therefore, you must perform proper maintenance on it.

People that live in areas with really hard water (lots of calcium and magnesium) may need to maintain their unit once every year, while people in areas with softer water (or those that have a water softener) might not do this every 4 or 5 years. Considering some of the best and most effective water softener systems that work with salt or water descalers working on electrical principles might also be a good idea.

Maintaining one of these units is a straightforward job. It will differ very slightly between manufacturers, but generally, it is just a matter of rinsing it with undiluted white vinegar. This will remove any limescale or mineral build up on the heating elements.

You can take a look at the basic maintenance procedure with this guide.

Best Tankless Water Heaters FAQs

Before we wrap up this guide, let’s answer some of the most frequently asked questions we received from users and people interested in getting a tankless water heater for their home.

Will I get instant hot water?

Actually, no you won’t. This is a common misconception about these types of heater. It will heat water instantly on-demand, but it will still need to travel through the plumbing lines. To get the instant hot water you need to install a hot water recirculation pump. These are available with many tankless models.

Do I need to upgrade the gas line in case I want to install a heater?

Yes, possibly as they need a bigger gas line. Tankless heaters need more BTUs because they use their energy over the period of a few seconds or minutes. A traditional system that uses a tank is able to use energy more steadily over a long period of time. The minimum gas line size is usually 3/4 inch and the size of the gas line upgrade will depend on the model and distance from the gas meter.

So it uses more gas than a traditional system?

No, they use the same BTUs. The traditional system heats more steadily, but they both use the same amount of energy to do the same work. The tankless unit will save energy as it has higher energy efficiency, and will only heat water when it is needed. A system with a tank will waste energy by continuously heating the water to maintain the desired temperature.

Why do some models need electricity and gas?

The gas supply is to heat the water. Most models are operated by digital controls. They use digital monitoring and have an electric ignition.

Will I need a water softener?

No, you don’t always need one. However, if you live in an area that has really hard water, then a water softener would help to prolong the life of the water heater. Some kind of water treatment system to prevent scale build-up in the water heater would be an advantage.

Will it save me money on my energy bills?

Yes. These systems are more energy efficient because they only heat water when it is needed. Traditional water heaters are lazy when it comes to energy efficiency because they are constantly in operation and use energy all of the time. If you choose a system with a really high energy efficiency ratings or an Energy Star certificate, you are likely to save even more each month.

Do they need regular maintenance?

They should be maintained around once a year. This is a simple job which involves rinsing the system with vinegar to remove limescale from the heating elements. If you have a water softener then this won’t have to be done as often. A whole house water filter would also help to prevent things like sediment from affecting the performance of the heater.

How much do they cost?

Tankless water heater prices vary widely. The prices change according to the size/output of the unit, energy efficiency rating, and general features a unit offers. The best tankless hot water heaters offer precise digital controls that let you strike an energy/heat balance that will save you the most money on your bills.

Do tankless water heaters last longer?

Tankless water heaters tend to cost more at point-of-sale than conventional “storage” water heaters. But the best tankless water heaters are known to last longer than their water tank storage counterparts, more than making up for the initial cost.

Water tank storage water heaters use continual heating to maintain constant hot water in their built-in tanks, causing more wear and tear on the mechanism. The lifespan of the tank is also an issue, as oxidation (rust) and mineral scaling limit the lifespan of most storage water heaters (stainless steel tanks are recommended if available).

Storage water heaters usually last between 10-15 years. But barring unforeseen mechanical failure, most tankless water heaters have a life expectancy of 20+ years.

Are electric tankless hot water heaters as efficient as they claim?

For homes with moderately-light hot water needs, on-demand water heaters can be much more energy-efficient than conventional storage-tank water heaters. The type of tankless water heater (gas-fired, pilot-light) will determine its actual heating efficiency. Proper installation and maintenance are necessary to optimize energy usage.

Is a tankless water heater reliable?

Tankless water heaters produce hot water at a rate of 2–5 gallons (7.6–15.2 liters) per minute, with natural gas or propane-fired heating unit producing higher flow rates than those of a tankless electric water heater.

But depending on the circumstances, there are situations where even the largest, most powerful natural gas or propane fired unit can’t supply enough hot water for large households when multiple users in multiple rooms require simultaneous hot water for long periods. In such cases, the addition of more hot water heating units in multiple locations can satisfy large demand.

Can a tankless Energy Star water heater replace a gas heater?

Yes, provided water heating is sufficient to supply hot water usage needs can be met. ENERGY STAR® estimates a typical family can save $100 or more per year with an ENERGY STAR qualified tankless hot water heater.

What are some advantages and disadvantages of tankless water heaters?

One of the worst things in the morning is trying to start your day and realizing your shower doesn’t have any hot water. It takes quite a few minutes for the water tank to get full again and heat up. By then, you could have already eaten your breakfast and been out the door. In addition, the water heaters cool and are reheated several times a day – even when you are not home. This is a waste of energy and racks up costs for your utility bills.

The good news is that you can cut some of these costs by installing a tankless water heater. Homeowners often cite endless hot water supply, additional storage space, and lower energy bills as the reason why they switched over to tankless water heaters. Just a heads up – tankless water heaters save money in the long run but their initial costs are much higher than tank models. The U.S. Department of Energy reported that gas-operated tankless heaters will save you an average of $108 per year over traditional tank counterparts. Electric tankless heaters will save you an average of $44 per year.

Even if the savings sound good, don’t get ready to go out and spend it all just yet. Remember that the initial purchase cost of a tankless water heater is expensive. In fact, they can cost up to three times more than the traditional storage heater right off the bat. A good deal on an electric tankless water heater would cost about $1,000. If you are looking for a gas-powered whole house tankless water heater, it could cost you more than $3,000. Keep in mind that not all homes are equipped to support tankless water heaters. You may need to hire an electrician before you attempt installation. Rewiring your house can cost you upwards of $5,000.

The Advantages of Using a Tankless Water Heater

Alright, let’s get to the good stuff. There are many advantages to investing in a tankless water heater. The most obvious benefit is increased energy efficiency and lower operating costs. One of the most common questions we encounter is ‘how much energy and money am I going to save?’ As we previously mentioned, you will actually be spending more money upfront when you invest in your tankless water heater. However, the operating costs you cut in the long run will be more than worthwhile.

You won’t have to spend money on standby heat anymore (aka waiting for your shower to warm up). A tankless water heater provides hot water on demand. You won’t have to wait for constant reheating. In addition, you will get an increased water heater lifespan. While typical tanks only last ten to thirteen years, tankless water heaters can last for up to twenty. If you are planning to stay home, you will save a big chunk of cash.

Did we mention you will be saving a lot of space too? If money and energy efficiency weren’t big factors for you, maybe some extra square footage will be. After all, traditional water heaters can measure up to five feet tall and two feet wide. While that might not sound like a lot of space off the bat, you would be surprised at how much space they hog. By comparison, tankless water heaters are about the size of a large computer.

The Downsides of Using a Tankless Water Heater

Okay, now that we have listed all of the pros of using a tankless water heater, it’s time to address the cons. Here are a few factors to take into consideration when shopping. First, tankless water heaters have a limited output. If you have a large household, and multiple people are showering in different bathrooms, doing laundry, and dishes at the same time, the water heater might not be up to the task.

Second, it comes with an additional cost. While typical water heaters might only cost $300 to $400, they can be as pricey as $1,000. They have come down significantly in price over the next few years. The idea is that you will make up the upfront cost in savings over the next few years. There is also an instantaneous energy requirement.

Another con is the installation process and cost. We highly recommend hiring a licensed professional when you trade your traditional heater for a tankless water heater. Besides moving out the old unit, you will need to make space work for your new heater. Electric systems may require an upgrade. For gas systems, you may need a gas line.

Beyond savings, tankless water heaters also save you space, last longer on average than traditional water heaters, and are better for the environment. They typically come with a longer warranty too (about fifteen years on average). Traditional water heaters have a six-year warranty on average.

Is a Tankless Water Heater Right for You?

Here are some factors to consider as you consider your purchase.

  • Demand: What needs do you have for a tankless water heater? Do you need it to heat up your water in one bathroom or in the entire house?
  • Type: Think about the requirements you need for installation. For example, an electric tankless water heater will require proper voltage, a circuit breaker, and more. Gas-fired styles need proper ventilation.
  • Location: Your heater needs to be within 50 feet of a power source.
  • Longevity: Did you know that a tankless water heater can last you for twenty years or more? This is twice the lifespan of a traditional heater.
  • Installation: Unless you are completely confident in your abilities, do not try a DIY method. Hire a professional, highly-rated plumber or A/C contractor to install your tankless water heater.

Tankless Water Heaters: Electric or Gas?

Have you decided to go tankless? Good for you. You’ll save money, space, and you’re being eco-friendly. But one question still looms. Should you choose an electric or a gas model? As you may have guessed, there are some pretty significant differences between them. First, there is the potential cost of rewiring your house.

However, you will be happy to know that electric tankless heaters operate with ninety-nine percent efficiency. They won’t qualify for Energy Star rating rebates though. You will find that gas-operated tankless water heaters are on average twenty-three percent more efficient than traditional storage version ones (which operate at 60% efficiency according to the Department of Energy).

On-demand heaters can be mounted on the wall and take up substantially less space than tank heaters. They can be fueled by either gas or electricity. What your decision should boil down to is efficiency. Tankless water heaters only produce hot water when you need it; it is energy efficient. A study by the American Council for an Energy-Efficient Economy reported that by eliminating storage losses, a tankless system can reduce energy consumption by up to ten percent. Recent figures from the Department of Energy also shows that a tankless water heater uses much less fuel compared to traditional heaters.

The DOE calculated that one-time costs are about $865 for a 50-gallon storage tank heater and up to $2,500 for a gas-fueled tankless water heater. If you have fifty gallons of water in a tank, two people can take showers in the morning while another person makes breakfast and you will still have hot water to spare. Tankless water heaters can supply two to five gallons of water per minute. Gas-fired heaters produce more hot water than electric units do. Despite their extensive sticker price, a tankless water heater is the best solution for your heating needs.

Think about it. How many of the rooms in your house are far from the main water heater? The cold water standing in the pipes could delay hot water delivery for minutes and you waste a lot of water running your shower in the process. Electric tankless units may be appropriate for small units. For those of you who think that a large water heater sitting in your basement sounds inefficient, you are right. Let’s consider your options.


Advantages include: instant hot water on demand, a longer lifespan for the heater unit, lower month-to-month costs, they take up less space than bulky water tank heaters, and theoretically as long as they are functioning properly they never run out of hot water. Most importantly they eliminate “standby loss,” the wasted energy used when traditional units reheat water repeatedly even when not in use (the water heater constantly uses energy to keep hot water in its water tank).


Disadvantages include inconsistent water temperatures, a higher initial unit installation cost, and (in cases where demand outraces heating ability) a limited hot water supply. Also, the installation of a water softening system might be necessary to ensure that an instant water heater operates properly without interference from mineral buildup and scaling.

Are tankless water heaters really better than regular water heaters?

It all depends on what you are looking for, and why. They can be a very efficient alternative and the perfect solution to the needs of a particular household.

Will a Tankless Water Heater Be Enough for My Household?

The answer depends on your household size and average water usage. Tankless water heaters are a great option for families looking to replace their age-old storage tank with something to reduce heating bills, save space, and provide a large supply of hot water. Think about it. Heating up your water storage accounts for the largest portion of your home’s heating bill. Going with an energy-efficient system will significantly reduce your monthly utility bills.

Tankless water heater installation may cost much more than a traditional water storage heater. However, it will pay for itself in a couple of years. With this said, a tankless water heater is not the perfect choice for every type of household. They cannot run out of the water, as they are designed to heat water on demand. But they can be overwhelmed by the demand if you have multiple showers or appliances running simultaneously. You may have seen that tank water heaters are numbered by their storage capacity. In contrast, tankless water heaters are ranked by their maximum temperature in relation to the flow rate.

What Dangers Poses the Use of a Tankless Water Heater?

Using any type of gas-powered system requires caution. Since most tankless systems run on natural gas, you have to use the same cautionary measures you would regularly. There is a potential for carbon monoxide leaks. However, a tankless system isn’t very different from a gas-powered heater. As long as you keep up with your annual maintenance checks, you should not run into any problems with it.

Generally speaking, tankless water heaters are safer than storage water heaters. Besides the caution of carbon monoxide, a tankless water heater is a safe piece of equipment to install in your home. There is no tank to overheat or dangerously increase in pressure. Tankless water heaters are safer for children to be around. Many of them come with overheating sensors and automatically shut down if the temperature rises too high.

How to Choose the Right Size for Your Tankless Water Heater

Since tankless water heaters are ranked by the maximum temperature at a given flow rate, you need to consider its application. Never try and save money by buying a smaller tankless water heater than you know that you would need.

Final Round-Up: Tankless Water Heater Reviews and Recommendations

That brings us to the end of our hot water heater reviews and guide. If you have any questions then please don’t hesitate to ask away. We promise to reply promptly. We’ll update this page as we find top-rated water heaters that we feel add any value to the guide.

If you have concerns and are looking for solutions to enjoy hot water no matter where you live, check out our guide on the best hot water recirculation pumps!

If you want to be kept up to date with any new reviews or new articles here at Water Filter Answers then you can follow us on Facebook or join our mailing list. There are links in the top right corner of the page. Don’t forget to use the comment section below to share your experiences with such products! Do you use any of these best tankless water heaters? Are you happy with your curent model? Do you have other suggestions to make to the community?

Hi I'm Jamie, teacher and owner/chief contributor at waterfilteranswers.com. We strive to bring you the most informative water filter reviews in the most intuitive and user friendly way. Besides offering advice on the water filter to suit your needs, we also post topical articles on water pollution and the environment. Stay connected and follow us on, Facebook, Twitter, Google+ and more!

  1. I love that appliances are becoming more and more energy efficient. It’s amazing how much one energy efficient appliance can save you. I’ve been trying to be more eco-friendly, so it sounds like tankless water heater could be a great option. Do you have any thought on solar powered water heaters?

  2. Hello,
    Thanks for sharing the great info about the water heater and also of a tankless water heater.
    I also found a site a site – https://www.reviewinstitute.org/rheem-tankless-water-heater/

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