9 Best Tankless Water Heaters of 2021 – Reviews & Top Picks
Last Updated on November 15, 2020
We all know the disappointment of feeling the shower water begin to turn cold as your water heater tank empties. You know your shower is coming to an end, whether you like it or not.
Keep turning the knob further towards the hot side if you wish, but it will be to no avail. Luckily, technology has found a way to provide instant and endless hot water, whenever we need it. All you need is a tankless water heater. But which one should you buy?
We were wondering the same thing, which is why we tested so many of them and wrote the following nine reviews to share the knowledge we gained. After reading them, you’ll also know which ones are worth investing in and which ones are best avoided.
A Quick Comparison of Our Favorites
|Best Overall||Ecosmart Water Heater||
|Best Gas Model||Takagi Water Heater||
|Best Value||Thermoflow Water Heater||
|Atmor Water Heater||
|Rinnai V Series Water Heater||
The 9 Best Tankless Water Heaters – Reviews 2021
1. Ecosmart Electric Tankless Water Heater – Best Overall
Digital temperature control and display on the front of the Ecosmart ECO 18 let you dial in your preferred water temperature in increments of 1 degree. This is a great improvement over other models that only offer a few heat settings to choose from, or come programmed with a single option. Even more impressive, this unit is covered by a lifetime warranty. The ECO 18 is fully electric and will require 240V hookups to run.
Our only real complaint with this model is that it only produces 2.5 gallons per minute of hot water. This is still better than many units that we tested while researching for this list, but it’s not enough to supply a home with more than a single bedroom. We did appreciate the compact design that can even be wall-mounted so that it doesn’t take up any floor space. In the end, we think this impressive list of features and instant, reliable hot water production adds up to the best tankless water heater we’ve seen.
2. Takagi Tankless Water Heater – Best Gas Model
If you’re looking for a natural gas tankless water heater, the Takagi T-K4-OS-NG is one we recommend above the rest. It’s got an incredible hot water production rate of 8 gallons per minute, which is enough to fuel the needs of a house with multiple bathrooms. Compared to most of the other tankless water heaters we’ve seen, this is a pretty impressive figure. It still needs electricity, even though it runs off natural gas, but you can just plug it into a standard 110V outlet.
This is an outdoor model, but a five-year warranty will protect your investment. We expected this meant that it would be able to withstand adverse weather conditions, but you’ll want to be careful in certain locations where inclement weather is common. Unfortunately, the warranty doesn’t cover bad weather, which is the biggest complaint we have about the Takagi tankless water heater. That said, when our heater had an issue, Takagi’s customer support was excellent and they took the time to make sure that our problem was resolved. For all these reasons, we think it’s the best gas tankless water heater.
3. Thermoflow Electric Tankless Water Heater – Best Value
Tankless water heaters can get very expensive, but the Thermoflow Elex 3.5 is a very affordable option that won’t break the bank. Despite the low cost, it’s an effective unit, which is why it’s our pick for the best value. It’s a very small device, measuring just 8”X 6”X 3”. Combine that with a weight that’s just under 2 pounds, and the Thermoflow Elex 3.5 is one of the lightest and most compact tankless water heaters that we’ve seen. Thanks to the small size, it can easily be wall-mounted in a discreet location where it won’t consume any space.
Of course, that tiny footprint does have a drawback, namely, the low flow rate of just 0.5 gallons per minute. This is sufficient for a single bathroom or a dwelling with only one resident. If you have more than just a single bathroom or several people living in your home, then its low rate of hot water production probably won’t be adequate for your needs. That said, the Thermoflow Elex is one of the cheapest ways to get instant and tankless hot water in your home.
4. Atmor Tankless Water Heater
To eliminate waste and reduce water consumption, the Atmor Tankless Water Heater only activates when sufficient water flow of over 0.5 gallons per minute is detected. This prevents your water heater from running continuously and running up your energy bill. But that’s not the only way this Atmor unit saves you money. It’s one of the lower-priced tankless water heaters to begin with, so you’ll be saving on your initial investment with this product.
The Atmor is an all-electric model, so no gas is necessary. That means it needs to be wired into 240V electric and it will require 4-gauge wire. You’ll likely need a professional to install this device. The ability to produce 2.25 gallons per minute of hot water means it’s no slouch, but it’s also not a top performer. If you have just one bathroom in your home, the Atmor tankless water heater will do well. But if you have multiple bathrooms, you’ll probably want more. While some units we tested allow you to dial in your water temperature settings to an exact degree, this one has just three options to choose from with low, medium, and high choices available.
5. Rinnai V Series Tankless Water Heater
The V65EN tankless water heater from Rinnai is one of the more expensive models that we tested, but we don’t think its value lives up to the price. That said, it does have some impressive features that are still worth mentioning. For instance, the Control-R 2.0 mobile app allows you to control this device from your smartphone. With the app, you can create schedules and timers and even put the unit into vacation mode. Also impressive is the 6.5 gallons per minute of hot water that the Rinnai can produce.
This a natural gas water heater that must be installed outside. The heat exchanger is protected by a 10-year warranty and the parts are warrantied for five years. However, repairs are incredibly expensive, and labor is only warrantied for one year. Expect to pay quite a bit out of pocket to fix any problems once you’re past that one-year mark, even though Rinnai will cover parts. Our biggest complaint was the low water pressure we experienced with this heater. Despite the high rate of hot water flow, our water pressure took a noticeable nose-dive after installing the Rinnai.
6. Rheem Residential Tankless Water Heater
It looks sleek and advanced, but the Rheem RTEX-13 Residential Tankless Water Heater only provides moderate levels of performance. We did like the digital thermostat control with a single knob for dialing in whatever temperature you prefer down to the degree. With a hot water production rate of 3.17 gallons per minute, it’s no slouch, but it won’t be fulfilling the needs of a home with multiple bathrooms. In fact, you may have trouble even running a single shower with this unit if you have a high-flow showerhead. In some parts of the United States, you may need to switch to an eco-friendly low-flow showerhead with a flow rate of 1.5 gallons per minute if you want this heater to adequately supply it.
For us, the real problem with this tankless water heater is reliability. Ours developed a leak after just a few weeks. We caught it early, but it could have turned into a major ordeal. With so many other well-functioning options available, we don’t think it wise to trust your water heating needs to a device that could potentially flood your home.
7. Stiebel Eltron Plus Tankless Water Heater
The digital temperature display and control set into the all-white body of the Stiebel Eltron Tempra 12 Plus looks pretty futuristic, but performs below average. You can easily set your water temperature to the exact degree you want up to 140 degrees. But you’ll only get 2.5 gallons per minute of hot water from the Tempra 12 Plus, which isn’t enough to supply most homes. On the other hand, if you just want to provide instant hot water for a single sink, this device is great.
Our biggest complaint with this tankless water heater is that it has a very short lifespan, something that’s very disappointing at such a high price. In our testing, we experienced unreliable operation that resulted in a dead unit after just a few weeks. After a call to Stiebel Eltron, we determined that control module issues are a somewhat common occurrence with this model. However, it’s protected by a three-year parts warranty and a seven-year leakage warranty. Even with the warranties, we prefer to invest in technology that won’t let us down the way that the Stiebel Eltron Tempra 12 Plus did.
8. ECOTOUCH Tankless Water Heater
It’s not too expensive, and it’s also not the best performer. The ECOTOUCH Tankless Water Heater is an average offering that just doesn’t supply enough hot water for most situations. With a max flow of just 1.8 gallons per minute, you’ll have difficulty even taking a hot shower using this device. If you have an eco-friendly low-flow shower head, then you may get away with it, but you won’t be able to use a sink or any other water source while showering. According to ECOTOUCH, it can only power a shower in the southern parts of the United States.
Despite the poor hot water production, this is an advanced-looking machine that’s all black with a digital temperature readout. You can easily adjust the water temperature to suit your preferences, but the highest you can set it is 131 degrees. For most tankless water heaters, 140 degrees is standard, so the ECOTOUCH is a bit below par. In the end, we don’t think this machine is a great value, even at an affordable price.
9. Eccotemp Portable Tankless Water Heater
Rounding out the bottom of our list is an interesting tankless water heater that’s fully portable. The Eccotemp L10 can be taken anywhere and provide you with limitless hot water instantly. To do so, you’ll need a standard 20-pound liquid propane tank to provide the gas. You’ll also require a water pump if you want to do anything with the water.
Thanks to its portable nature, the Eccotemp L10 is an excellent device for supplying water to RVs, tiny homes, greenhouses, and more. However, it’s not adequate for a full-size home, even though it has a somewhat decent hot water production of 3 GPM. For supplying a home, if you’re using a natural gas tankless water heater, you’ll want one that hooks into the gas supply for your house so you won’t have to constantly refill your tank to meet the daily demands of an entire household.
Now that we’ve compared some of our favorite tankless water heaters, let’s discuss some of the benefits of them. For many years, water heaters with tanks have supplied most residences with their hot water needs. These tankless heaters are relatively new, but what makes them so appealing?
Unlimited Hot Water
Gone are the days of your shower turning cold when the water heater tank runs dry. A tankless water heater doesn’t need to keep a supply of hot water on hand to deliver when you turn on the faucet. Instead, they heat the water as it goes through the device. This means you can have an endless supply of hot water since the heater will just continue heating more of it as it passes through.
Instant Hot Water
When you turn on the hot water in most homes, you have to wait until the water gets warm. But with a tankless water heater, the water will get hot instantly. No more waiting for the shower to get hot! Just turn the knobs and hop in. This is a great time-saver, but it also allows you to conserve water since you won’t waste so much just finding the right temperature.
It takes a lot of energy to keep a large tank of water heated up to deliver when needed. Luckily, a tankless water heater doesn’t need to keep any hot water on hand since it can instantly heat the water it needs. This saves a lot of energy that would have been wasted keeping the tank full of hot water.
What to Look for in a Tankless Water Heater
Now that you know the benefits of a tankless water heater over a traditional water heater, let’s discuss what you should look for when deciding which one to purchase. While they all perform the same basic function, they have different abilities and features that set them apart from one and other. The following traits are what you should think about when making your decision.
Hot Water Production Flow Rate
A tankless water heater can provide unlimited hot water, but only if it can heat water fast enough to meet the demands of your home. Each unit will have a certain number of gallons per minute (GPM) of hot water that it can produce. If you live alone or have just a single bathroom, then you may be ok with a device that can only provide 2.5-3.0 gallons per minute. On the other hand, if you have multiple bathrooms or more than one person residing in your home, then you may need considerably more flow.
Where you are located also plays a part in how much hot water a tankless water heater can produce because it will affect the temperature of the water coming into the heater. In the northern United States, tankless water heaters will produce fewer gallons per minute than in the southern states.
Some of these devices come preset from the factory for a certain temperature of the water. But this can usually be adjusted to fit your personal preferences. For some devices, this is done by selecting a power level, often low, medium, and high. Some of our favorite devices featured digital displays and thermostats that make it easy to dial in an exact temperature setting for your hot water, even down to the exact degree you want.
Your water heater gets put through a lot of work. Every single day you’ll ask it to heat dozens of gallons of water, some days even more. Eventually, your machine could experience problems or even complete failure. When this happens, you’ll be wishing you had a warranty. Thankfully, many manufacturers include warranties with their water heaters. The warranty may be different lengths for different parts on the same device. For instance, the heat exchanger may have a certain length warranty, say 10 years, while labor has just a one-year warranty. This could be on the same water heater, but you’ll have to expect different repair costs based on what part goes out. To be safe, you could just look for a unit with an included lifetime warranty that will keep you covered no matter what happens.
There are quite a few tankless water heaters available today, and if you’re trying to choose between them, the decision can seem quite difficult. Our reviews should have helped you narrow down the field, but to take it even further, we’re going to reiterate our top recommendations. In our eyes, the best overall tankless water heater is the Ecosmart ECO 18. Its compact design can be wall-mounted so it doesn’t take up any space. Plus, it requires no natural gas, features digital temperature control, and is even protected by a lifetime warranty.
For the best natural gas model, we think the Takagi T-K4-OS-NG is a clear standout. With an impressive eight gallons per minute hot water production, it’s one of the few models that can supply a house with multiple bathrooms. It plugs into standard 110V electric and it’s covered by a five-year warranty. Finally, for the best value at an affordable price, the Thermoflow Elex 3.5 is pretty hard to beat. It’s tiny so it doesn’t waste space, it’s affordably priced, and it can even be wall-mounted. We don’t think you could go wrong with any of these three devices.