10 Efficient Tankless Water Heater Reviews – Make the Right Choice in 2024

This innovative water heater from Rinnai uses advanced technology to bring you steaming, hot water.

This unit is able to instantly heat water because of the heating elements installed within its piping system. Let’s break down its features and get a better look at why this heater makes it to our top ten list:

Let’s dive into the details…

First of all, we found this water heater to be a powerful, whole house unit. Our testing proved it to have a massive capacity. In fact, it can put out up to 7.5 GPM of hot water at a time. This makes it perfect for large-sized residential, or even commercial, applications.

Simply put, it’s enough to run 3 to 4 full-flow showers simultaneously. That’s a tough standard for other tankless water heaters to top.

On top of that, this Rinnai model is not lacking in the energy efficiency department either. With an energy factor of 0.82, this device showed us it can save its owners a reasonable amount on their utility bills. It even comes with an Energy Star certificate for your assurance!

Environmentally Friendly: This unit is also SCAQMD-certified for reduced fumes and emissions of carbon dioxide.

You know what else we thought made this tankless water heat great? The amazing technology and advanced controls!

The Rinnai RL75iN comes with a digital controller that shows the user if there are any issues the unit is facing. It makes troubleshooting a breeze and indicates error codes (you can check the manual for what they stand for, their importance, and how to solve them). We loved the simplicity of this feature.

You can also control the water temperature and set it as hot as you like. For residential applications, you can choose from between the range of 98 to 140F. For commercial applications, the temperature can range from 98 to 160F.

Moreover, it also comes with a leak detector, which stops the water supply if a water leak is identified. Another cool feature is the temperature lock. This locks the temperature setting to prevent any unauthorized adjustments and changes.

Since scale deposits can shorten the life of a water heater, and lead to damage or breakage, we were especially impressed with the scale deposit detector this unit is equipped with.

And that’s not all that impressed us. The Rinnai RL75iN’s space-saving and convenient design had us swooning. It’s not very large sized, and its sleek, silver design won’t look like an eyesore in any part of your house.

This unit comes with a 10-year warranty for the heat exchanges, a 5-year warranty on the parts, and a 1-year warranty for residential installation. Keep in mind the warranty is only valid if you get the unit installed by an authorized Rinnai service provider.

The only negative part about this excellent water heater is its price. But if you look at the long-term benefits, it can really be worth it. Especially if you want to invest in a whole house water heating system for a large residential or commercial place.

Plus, with all the advanced features and controls, this unit can run perfectly for 20 years if maintained properly. Maintenance isn’t much of an issue either because this intelligent device always informs you whenever there is a problem!

Features:

• Comes with a digital controller and Error Code Indicator
• Residential temperature range: 98°F – 140°F
• Commercial temperature range: 98°F – 160°F
• Energy Star Certified
• Leak and Scale Deposit Detector

This German-engineered water heater is one of the best electric models out there for larger families, houses, condos, and even smaller commercial areas. It’s designed to work great in both warmer and colder climates.

Here’s why we love it…

First, it’s a total powerhouse. In fact, it slightly improves over the Rinnai RL75iN from above. With a powerful capacity to put out up to 8 GPM of water, this water heater can easily provide hot water to four showers at the same time.

Aside from a high flow-rate, it’s self-ventilating and comes in a compact size designed to save space. This means you can pretty much fit this water heater anywhere in your house without taking away from the aesthetics of your house.

Another great thing about this incredibly powerful model is it comes with self-modulating technology, which adjusts the power output according to any changes or fluctuations in the incoming water temperature.

We know everyone loves to save on their electric bills and the Stiebel Eltron Tempra Plus makes it possible. We discovered it has a super high energy efficiency of 99.5%, so you are sure to save on your energy expenses. This is great if you want to invest in a heavy-duty water heater for your house, but don’t want to increase your energy costs in the long run.

This Tempra Plus model also features an interesting Advanced Flow Control technology. This little perk lets the heater adjust its flow-rate to keep the output temperature the same as you set it. This means no matter how many water outlets you use, the water temperature will stay the same. This water heater will simply adjust the flow-rate accordingly.

The handy digital temperature display on this product is also a great feature to have. You can adjust the water temperature to any desired level between 86 and 140F.

This German product also comes with a thermostatic temperature control feature, which regulates the temperature to prevent any fluctuations during your usage. This basically means you’ll never have to worry about streams of cold water in between your hot showers anymore. That certainly one of the reasons we ranked this model so high.

Some things to be aware of…

Now, we aren’t saying this tankless water heater isn’t great. But like every other product out there, it comes with a few potential drawbacks you should at least be aware of before you start spending.

This water heater isn’t cheap. But, considering its massive capacity, the price seems fair to us. Plus, it saves your electricity costs in the long run, which really makes it a cost-effective option. However, getting it installed by a professional might increase your costs significantly. You might be tempted to try a DIY install, but that would just waste this product’s warranty.

Speaking of warranties, this Tempra Plus model comes with a 3-year warranty, but only on its parts. This is a little unfortunate because some users have reported their heater broke down after several months and the warranty didn’t apply to the whole unit.

The point is, be careful before you make your purchase decision. Nevertheless, this heater mostly has great customer feedback and is designed to work perfectly in colder areas, as well as in warmer climates. If you want to invest in an efficient electric heater suitable for a large residence, this is a solid option.

Features:

• Digital display
• Advanced Flow Control technology
• 36 kW's of power
• Thermostatic Temperature Regulation
• Requires 300 Amp service

This Rheem model is definitely one of our favorites.

If you have a large household, a consistent supply of hot water in cold weather can be a big problem. But if you’re willing to invest in a water heater guaranteed to put an end to all your worries, this is the one.

This high quality, powerful indoor water heater delivered an impressive flow rate of up to 9.5 GPM. That’s enough to instantaneously run two or three full-flow showers and a kitchen full of appliances.

But that’s not the only good thing about it…

Apart from its massive capacity, this product comes stuffed with tons of other features.

For starters, it comes with a stainless steel heat exchanger and uses condensing technology to heat water. This makes it extremely energy efficient. In fact, it has a certified energy factor of 0.94, which means you get to save a huge amount on your monthly bills. It also comes with intelligent electronic controls that further increase its energy efficiency.

Unlike other heaters powered by natural gas, this Rheem model uses an innovative venting system (low-NOx) that reduces fumes and emissions. It can pretty much be fitted anywhere inside or outside the house. It isn’t very heavy or large-sized either, considering its powerful output capacity, which makes it convenient to fit indoors.

Another great thing about this heater is you can fit several units together using special cables for additional use, such as for serving a larger house or even a commercial area.

Wait, there’s more:

That’s right. This water heater features more techy features. It comes with a digital display that shows temperature settings and maintenance codes, and a built-in self-diagnostic system for convenient troubleshooting. It also comes with a remote control, so you can easily change its settings from a distance. We loved the convenience of this.

It also comes with freeze protection and supports altitudes of up to 8,400 foot above sea level, which is why we recommend it for use in higher elevations and colder areas.

This natural gas heater also has safety features we couldn’t overlook.  You don’t have to worry about it being a hazard, especially when you’re installing it indoors.

It features a hot-start system that prevents fluctuation water temperature during on-and-off operations and also comes with a patented Overheat Film Wrap technology that protects against problems with the heat exchanger.

Unfortunately, all good things come at a price. And this heater literally comes with a pretty steep price tag. That’s the only downside of it, along with the company’s reputation for offering terrible customer service. But since it reduces maintenance and energy costs in the long run, it’s a really good investment for people with larger families and a constant need for hot water.

Features:

• 94% Energy efficiency using stainless steel condensing heat exchangers
• SCAQMD rule 1146.2 compliant
• Compact design
• Self-diagnostic system for easy installation and service
• Built-in electric blower

First of all, this indoor natural gas water heater offers GREAT value for money. It’s much more affordable than its competitors and comes packed with advanced features. It provides a consistent flow rate of up to 6.6 GPM--perfect for any small-sized family home.

Let’s take a look…

To start off, this model is the smallest one from Takagi’s line up.

It has a pretty convenient size for the capacity it offers, which makes it a great buy. You can fit it anywhere in the house because of its compact dimensions. It also weighs less than 30 lbs. This makes it a relatively lightweight option compared to other models.

Secondly, it comes with an Energy Star certificate that guarantees efficient use of energy and water. If you look at energy factors, this model boasts a high energy factor of 0.83. This means it produces a lot of hot more compared to the energy used.

This gas-powered water heater offers a consistent flow rate of up to 6.6 GPM. In our testing, it easily produced hot water to multiple water outlets at the same time.

This Takagi model also comes packed with a lot of different features that sparked our interest.

One of them is the use of thermistors that constantly monitor and regulate the water temperature. When we tried this unit out, we impressed at how well this feature worked. It greatly reduced the problem of fluctuating water temperatures, regardless of the outside temperature.

We enjoyed the remote control that shipped with the water heater because it made for simple adjusting of the water temperature to the desired level. The remote also as has advanced switches for adjusting the performance for different altitudes. The maximum altitude allowed is 6000-foot and can be adjusted using the DIP switches inside the heater.

More features of this indoor model we thought were worth mentioning include an AFR (air-fuel ratio) sensor for keeping efficiency in check and tons of safety controls.

Gas-powered products are great, but they naturally require some safety mechanisms. This Takagi model offers a lot of them. It comes with frost protection and a flame sensor. Similar to other models we reviewed, it also automatically turns itself off in case it overheats. This makes it a really good option for families who are extra careful about using such appliances indoors.

Of course, because this is a gas-fed water heater, it requires outdoor venting.

All in all…

This Takagi indoor gas water heater offers great value for the money. It’s energy efficient, comes packed with useful features, has a lot of safety controls, and offers a decent flow rate.

Plus, a lot of customers we spoke to were happy with its operational longevity, which means it’s likely to work perfectly fine for years to come.

If you have a small family, this is a great option for you. For larger households, though, not so much.

Features:

• Energy Star Certified
• Includes remote controller and power cord
• Venting with Category III stainless steel
• Safety features: freeze, overheat, surge protection, and troubleshooting diagnostic codes

This powerful, heavy-duty tankless water heater from Rinnai is one of their most efficient models.

This unit operates on both natural gas and propane and is designed to be installed indoors. It offers a massive flow-rate of up to 9.8 GPM, which means endless water supply to a large residential or even a commercial place. You will never have to worry about running multiple water applications on this tankless model.

Note: This unit can activate at just 0.4 GPM too.

We think the Rinnai RUC98iN is more than just the average water heater since it offers tons of benefits. It is energy efficient, saves space, and has a low environmental footprint.

Let’s take a closer look…

Aside from offering such a high flow-rate, this model also comes with special venting options. The concentric/twin pipe PVC venting made it easy to assemble and set up, although we do recommend getting a professional to do it for you.

That being said, Rinnai does also accept your DIY installation, on the condition that you get it inspected by a certified plumber.

But since it weighs a hefty 82 pounds, this water heater can be a little difficult to install on your own. The good thing is, it has a space-saving design and can be easily mounted on a wall with some help. This means its heavyweight won’t make much of a difference after you’ve installed it.

The Rinnai RUC98IN was also one of the quietest tankless water heaters we tried out. This is because it uses advanced low-NOx technology, which effectively reduces fumes and emissions. The low-NOx feature is also great for the environment and cuts down on both air and noise pollution.

Also, this model has an energy factor of 0.96, and it helps that it comes with an Energy Star certificate. It’s highly energy efficient and you’ll save tons on your utility bills. Plus, since it works on natural gas, you will automatically cut down on costs. That’s because gas-powered heaters are much more efficient than electric ones.

It offers a hot water temperature range of 98F-140F for residential installations. There is a commercial installation option that can be purchased separately which will boost temperature outputs to 185F. It also comes with an MC-91-2US remote controller, which lets you easily set the water temperature from a distance.

Moreover, this Rinnai water heater is incredibly durable and is known to last for a very long time. It also comes with two different types of warranties:

• Residential: Limited to 12 years on heat exchanger, 5 years on parts, and 1 year on labor (5-year optional on labor).
• Commercial: Limited to 5 years on heat exchanger, 5 years on parts, and 1 year on labor (2-year optional on labor).

The only downside that we see in this powerhouse of a water heater is its price. It costs a lot, we won’t lie. But then again, you get an amazing water heater with guaranteed longevity, energy efficiency, and high-end technology to save you a lot of costs and frustration in the long run.

The bottom line is, if you are looking for a great, long-term option for your large-sized residential or commercial place, we definitely recommend you to consider investing in this Rinnai model.

Features:

• Energy Factor: 0.95 for Gas and Propane
• Temperature Range: Residential: 98°F–140°F/Commercial: 98°F–185°
• Ultra Low NOx
• Venting Options: PVC/Concentric PP
• MC-91-2US controller included

Here is another excellent option for medium to large sized families.

Depending on your area and the incoming water temperature, this tankless water heater can provide a high flow-rate of up to 4.5 GPM. That’s enough for two showers and a sink running all at the same time, but it isn’t as powerful as other options that made our list. Of course, for smaller families, this may not be a concern.

Check out the innovative heating system…

The cool thing about this unit is it uses the unique, Quartz infrared technology to heat water. This efficient system eliminates the need for coils and keeps water away from any kind of contact with metal. The best part is, you still get constant steaming, hot water always available for use.

Because of its coil-less technology, this SioGreen model prevents corrosion and unwanted buildup of limescale and calcium deposits. People who live in areas with well water or hard water often face this frustrating problem, but SioGreen completely eliminates it. This is especially useful because it automatically extends the life of this unit, and makes it pretty much maintenance-free for years to come!

Moreover, this innovative infrared technology in a tankless water heater also makes sure algae or bacteria doesn’t build up inside your unit.

Aside from its unique heating system, we really liked this model’s energy efficiency. It comes with self-modulating technology, and only heats up the water you use. This is great news for both your electricity bill and the environment as a whole because you’ll be saving both water and energy.

This tankless unit comes with adjustable temperature controls, so you can set the water to be as hot as you like. It also features a Safe Recovery mode, which isolates any issues in case a problem occurs, and continues to provide you with hot water without completely shutting off the system.

Is it easy to install it?

Because this unit is powered by electricity, it doesn’t require any expensive venting to be installed. But if you’re going to replace your old tank system with this tankless one, you might face some hassle and issues with setting up your existing plumbing.

Overall, this SioGreen model is a great option on its own for medium and large houses. It offers a decent flow-rate, comes in a compact size, and saves on your electricity bills. Plus, the Quartz infrared technology also prevents corrosion and limescale buildup.

WARNING: Some customers have complained about this unit not functioning well in very cold climates (below 50F).

When it comes to the price, this unit doesn’t come cheap. But considering the fact that it’s maintenance-free and energy efficient, it will save you tons of money in the long run.

Also, the innovative heating system significantly extends this water heater’s life, so you can be sure it will stay with you for years to come. We consider this a pretty good investment.

Features:

• Quartz infrared coil-less technology
• No corrosion & free of maintenance
• No calcium & limescale deposits
• Save water & energy

In our opinion, this EcoSmart model is another excellent option for smaller homes and families.

This efficient little water heater works best in climates with incoming water temperatures of 67F or more. Despite being relatively more affordable than other options, this model offers pretty decent specs, features, and performance.

Lots of customers and experts are satisfied with their purchase of this water heater. But let’s go into some more detail so you can find out if it’s perfect for you or not:

The EcoSmart Eco 11 model is an electric-powered tankless water heater best known for its energy efficiency. In fact, with this model’s energy efficiency of around 99.8%, EcoSmart’s manufacturers claim this water heater can help you save up to 60% on your energy bills!

This small-sized unit can provide up to 2 GPM of hot water, which is good enough to take one steaming hot shower and run a bathroom or kitchen sink faucet simultaneously. It is also incredibly lightweight and can be used as a point-of-use (POU) heater in colder climates.

The Eco 11 features a self-modulating technology that automatically adjusts water temperatures to provide you with consistent hot water. It only uses power to heat the water you are actually using. This saves big time on your electricity bills and prevents water waste.

When it comes to installing this unit, you’ll be amazed at how easy it is. A 60-amp power supply coming from a double pole breaker, and a #6 copper gauge wire is all you need to set this up.

This eco-friendly water heater also comes with a digital temperature control, which supports up to 1-degree increments. You can adjust the water temperature just the way you like to up to 105F.

Favorite perk:

The thing we liked best about this water heater is, it comes with a lifetime warranty. That’s right. You will never have to worry about wasting your money on this because any issue you face can be easily addressed without costing you a penny.

All in all, this efficient and ‘smart’ unit is relatively affordable and designed for use in smaller homes. One downside is it’s not really useful as a whole house unit in climates with incoming water temperature less than 67F. You might have to use it as a POU unit on cold days, and that’s not very practical.

Some customers we talked to complained about fluctuating water temperature in this heater. This means you can go from warm to scalding hot or ice cold for no reason in the middle of your showers, which can be pretty dangerous.

Ending on a positive note…

This is an electric-powered heater. This means you don’t have to worry about venting or any of that stuff. Compared to gas-powered water heaters, this will help you save on installation costs, time, and space.

TIP: Consider purchasing this unit if you already have an existing water heating system and need some extra hot water, or if you have less use of hot water where you live.

Features:

• Save up to 50% on costs
• Advanced self-modulating technology
• Stylish design
• Digital temperature control with 1-degree increments
• Copper/stainless components for efficiency, durability and easy replacement
• Compact size

This innovative electric water heater is great for single faucet use. If you need instant hot water for only a kitchen or bathroom sink, dishwasher, an outdoor faucet, or even a low-flow shower head (although, not recommended), this model is perfect for you.

There are so many good things about this product. It’s conveniently sized, easy to install, resists corrosion, and prevents the buildup of limescale, algae, and bacteria.

But that’s not all…

The most unique feature of this point-of-use (POU) model is it uses coil-less, quartz infrared technology to heat up only the water you use. This makes it an extremely energy efficient and safe option for you and your family.

Also, because it doesn’t use metal coils like most other electric water heaters, water doesn’t come into direct contact with the metal parts. While metal itself is not much of a problem, constant contact with water may lead it to break down after a while. The coil-free technology used in this heater means no corrosion and no buildup of limescale and calcium deposits.

Offering a flow rate of up to 1.5 GPM, the SioGreen IR260 effectively heats water on demand with self-modulating control, which means it won’t activate when you’re not using any water.

This compact water heater is also maintenance-free and self-cleaning. In fact, it claims to be able to work perfectly fine for over 20 years of continuous use. Think of how cost-effective that is!

For your convenience, it also comes with a digital temperature control so you can set it as you like.

To suit its purpose, this tankless water heater comes in one of the smallest sizes in the market and weighs only 5 lbs, so you can install it in just about any space you want. Moreover, installing it is super easy, and you don’t really need an expert to do it for you (although it is always recommended). SioGreen provides ample walkthroughs and installation support on their website.

However, there are some concerns with this model…

The product clearly points out that the incoming water temperature should be at least 72F for a 1.5 GPM flow rate, which means it’s not very effective if the water in your area is usually colder than that.

Also, even though you can use it for a low-flow shower head, it’s not intended for shower use. You might also face trouble if it doesn’t produce enough steaming hot water for your everyday needs at times, such as quickly filling up a bucket.

Overall…

This compact-sized, point-of-use water heater is a great bet for its competitive price. It barely requires any maintenance and has a pretty long operational life. Its resistance to corrosion and buildup makes it a great option for use in areas with hard water or well water. Moreover, it is incredibly energy and cost efficient because it only heats up water during use.

Features:

• Quartz infrared coil-less technology
• No corrosion & free of maintenance
• No calcium & limescale deposits
• Save water & energy

This Ecosmart model is a powerful electric water heater with the capacity to provide steaming hot water to your whole house.

This tankless heater has a flow rate of up to 8 GPM, which is a lot! This means it can concurrently provide hot water to multiple water outlets located in different parts of your house. It’s perfect for larger families where multiple bathrooms, kitchen, and laundry often need hot water supply all at the same time.

Another great feature is the digital temperature control on this model. What makes this digital control so unique is you can adjust it even to one-degree increments. This means you can set the temperature to the exact degree and get the water to be as hot as you like.

Moreover, this water heater is self-modulating, which means it helps you save a lot of electricity costs by only expending energy when needed.

The Ecosmart 36 electric water heater is also much smaller in size compared to its competitors, considering the capacity it provides. That’s because it is built for indoor installation. It also has detachable parts you can easily remove and replace if necessary, without having to replace the whole unit itself.

The lifetime warranty that comes with this product isn’t a bad perk to have either. Although, it does have a catch. Your warranty won’t be of any use if you don’t get your model installed by licensed plumbers and electricians.

All in all, this model promises a lot to its buyers. It offers a great flow rate, a convenient size, a handy digital control, a lifetime warranty, and so much more. Plus, the customer service this company offers is great, which is an always a relief.

So what’s the catch?

Well, some customer reviews tell a slightly different story…

Yes, we know about all the amazing things this product boasts of. But during our research, we found that some customers weren’t too happy with their purchase.

Mostly, it was because the Ecosmart 36 didn’t deliver what it promised. Some complained about the water not being as hot as set on the temperature control. Others found an issue with the operational longevity, with some products breaking down within just a few months. Some also found the startup to be slower than other tankless water heaters. We also found several reviews complaining about flickering lights in the house, especially in colder areas where the heater needs to use up a lot of electricity to heat the freezing water.

Despite some of the negative reviews surrounding the product’s performance, it is still worth a shot if you get it installed properly by professionals. You get a lifetime warranty, so any issue you face can easily be fixed!

Features:

• Good quality design and build
• Compact and space-saving
• Endless hot water supply at the coldest climates
• Cost-effective
• Digital temperature control

Do you love the outdoors and find yourself constantly going on adventures?

If yes, you must be familiar with the dire need of warm water on these trips. This Eccotemp portable outdoor water heater will be a great addition to your list of must-haves the next time you decide to head out into the wild.

There are so many good things about this handy little product.

First of all, it offers a pretty decent flow-rate of up to 2.65 GPM. That’s perfect for running two or three low-flow water outlets simultaneously. It can’t get any better at this price, too!

Note: The Eccotemp L10 Portable Outdoor Tankless Water Heater is powered by propane and ignited using two D batteries.

Moreover, it is incredibly easy and simple to set up and comes with all the necessary attachments. It’s also designed to be lightweight enough to carry around with you anywhere you go. With this portable model, you won’t have to waste your energy trying to drag a heavy-weight water heater to fulfill your hot water needs out in the open.

More to love about this product…

This useful water heater also comes with all the essentials you need to make it work like a charm. When you purchase this product, you also get a CSA-approved gas regulator and a hose to be used on a 20-pound grill style tank with it.

The gas regulator is there to keep you safe from any potential hazards, so it’s a great freebie to have. It also comes with a stainless steel rain cap, a garden hose adaptor, and other essential installation accessories.

It is designed to be portable and easy to carry around and use. Lightweight and durable, this heater runs on two D batteries for flame ignition and you can hook it up to a propane source anywhere you want.

Another great thing about this heater is it’s designed with safety in mind. It comes with an automatic shutoff timer, which turns the heater off after 20 minutes. This not only helps keep you safe from getting burned but also prevents any wastage of water in case you forget to turn it off.

This unit also features manual temperature controls with a range of 80-150F, so you can set it just the way you like. You can also adjust the flow-rate to set the right temperature. A low flow-rate will give you scalding hot water, and as you increase the flow, the temperature will automatically decrease.

Now, let’s talk about the installation.

This water heater is generally pretty easy to set up. It comes with a detailed instruction manual and all the necessary attachments/accessories to help you out.

A word of caution…

This water heater is known for sometimes being irregular in its water temperature. This means you risk getting burned by scalding hot water unexpectedly, or maybe even unwanted, cold water at times.

Plus, some customers say they find the product and its parts cheap and low-quality. Moreover, Eccotemp’s customer service doesn’t have a good reputation either, so if guaranteed quality is important to you, you might want to consider other options.

The good thing is, this product doesn’t cost much at all. In fact, the capacity and features it offers are amazing compared to its price.

It’s really not a bad buy for something you’d want to use only during your outdoor trips and adventures. Keep in mind, however, this heater is not supposed to be installed permanently outdoors. It is meant to be portable, so you should not expect much good out of any other kind of usage.

Features:

• CSA regulator for use with 20-pound grill propane tank
• Includes stainless steel rain cap
• Garden hose adapter included
• Outdoor installation only
• 2 D battery ignition
• 20-minute automatic safety shutoff timer