Tankless water heaters are transforming the way we get hot water to our sinks, showers, and other fixtures. They save space, are efficient, and can provide unlimited hot water. This makes them a hot item for homeowners and residential contractors alike.
Below find my picks for the best tankless water heaters of 2024.
Wondering how I picked them? Check out my best tankless water heater criteria.
| Best Tankless Water Heater | Best Gas Tankless Water Heater | Best Electric Tankless Water Heater | Best Propane Tankless Water Heater | Best Point of Use Water Heater | Best Commercial Tankless Water Heater |
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A.O. Smith has long been the gold standard in water heaters, and this proves why. The A.O. Smith X3 gas tankless water heater provides years of uninterrupted service thanks largely to its hallmark X3 scale prevention technology.
This innovative capability prevents minerals from forming harmful deposits on the heat exchanger and eliminates the need for manual descaling. In fact, it extends the heater's life up to three times longer than competing units! What's more, the copper heat exchanger is corrosion-resistant and provides better heat transfer than stainless steel.
Efficiency-wise, the X3 carries a 0.93 UEF because its condensing technology minimizes heat loss from the exhaust. It also meets Ultra Low-NOx emission requirements found in southwestern states. From a water-saving perspective, the X3 is approved to work with an external recirculation pump and cross-over valve, so you get immediate hot water. No more having to wait through those initial cold blasts.
A.O. Smith backs this water heater with an amazing five-year warranty on parts and a whopping 15-year warranty on the heat exchanger! You are truly getting a reliable and efficient unit for the price. If you want an easy answer to "what's the best tankless water heater?" the A.O. Smith X3 is it.
| Reliability |
| -Scale prevention tech eliminates annual descaling -Heavy-duty, corrosion-resistant copper heat exchanger -Built-in freeze protection -Overheat cutoff fuse; temperature safety controls |
| Efficiency |
| -Condensing tech -UEF of 0.93 -Energy Star Certified -Meets Ultra Low-NOx emission requirements -Will work with an external recirculation pump |
| Warranty |
| -15-year heat exchanger warranty -5-year parts warranty |
| Overall Value |
| Unbeatable reliability and performance at a fair price. |
For those who need a natural gas tankless water heater, the Noritz NRC98 stands out for its reliability and efficiency.
Thanks to its commercial-grade copper heat exchanger and thick piping, it'll provide hot water for years of hour-long showers, dirty dishes, and soiled clothes. A durable steel case with a polyester coating protects internal components.
If there’s even a chance something is going wrong, the NRC98 will respond with a suite of safety devices, including a flame sensor, overheat prevention, freeze protection, and condensate overfill.
You can even use this unit in heavier-duty applications by linking it with a second unit for twice the hot water capacity! It can be installed outdoors or indoors with direct or non-direct venting.
Efficiency-wise, you’ll save energy and money thanks to its Uniform Energy Factor of 0.91 and Energy Star Listing, made possible by condensing technology. Furthermore, direct electronic ignition eliminates the need for a constantly burning pilot light, saving fuel.
I also think the limited warranty is extremely competitive—12 years on the heat exchanger and five years on the parts. Overall, this unit will make you take hot water for granted, and isn’t that the point?
| Reliability |
| -Commercial-grade copper heat exchanger -Durable Steel Case -Built-In Safety Devices |
| Efficiency |
| -Can Link with A Second Unit -Uses Condensing Technology -UEF of 0.91 -Direct Electronic Ignition -Energy Star Listed |
| Warranty |
| -12-year heat exchanger warranty -5-year parts warranty |
| Overall Value |
| Everything the average homeowner needs from a water heater at a great price. |
The Eemax HA027 electric tankless water heater is nearly 100 percent efficient and very simple to install. Since it runs on electricity, you don't need to worry about venting or having a natural gas supply. It's easily wall-mounted and has simple compression fittings that don't require soldering.
The Eemax HA027 provides plenty of hot water for washing and personal hygiene. Its different models can provide up to 4 gallons per minute with a 60° F increase in temperature. Copper immersion heating elements with a threaded brass top help maximize durability and make for easy replacement. The external display and controls allow you to easily view and adjust the temperature by degree.
One major point to note, however, is that the Eemax, and all electric tankless water heaters, have an immense power draw. For example, the 3 GPM Eemax has a current draw of 113 amps and a recommended breaker size of 120 amps. That's too much for homes with 100 - 200-amp electrical panels to handle. If you decide to go with an electric tankless water heater, you may need to work with your electrician and utility company to upgrade your service, wiring, and/or electrical panel.
Making those upgrades can definitely be worth it, though, especially if you lack access to natural gas and need electric-powered solutions. The unit comes with a 1-year warranty on parts and a 5-year warranty on the heat exchanger. If you have the ability to use it, definitely go with the Eemax HA027 for your water heating needs.
| Reliability |
| -Copper immersion heating elements -Precise external temp. controls -Flexible installation |
| Efficiency |
| -Efficiency of 99% |
| Warranty |
| -5-year heat exchanger warranty -1-year parts warranty |
| Overall Value |
| Efficient and effective water heating solution if you have the electrical service to handle it. |
If your life runs on propane, then the Rheem RTGH propane tankless water heater is your best bet.
This condensing unit has a Uniform Energy Factor of 0.90 and includes a water savings setting that limits water flow until it's hot enough to use. In other words, you won’t waste as much cold water waiting for it to turn hot.
Related to this is the Hot Start Programming feature, which keeps the water heater ready in between uses, cutting down on those nasty cold water bursts we all hate. When you don’t need much hot water, no worries. This Rheem water heater will activate when it senses a minimum flow rate of 0.26 GPM, which is great if you have water-saving appliances.
You’ll get an impressive 15-year limited warranty on the heat exchanger plus five years on the parts. A leak detection system helps prevent water damage for additional peace of mind.
Overall, the amazing efficiency features make this propane tankless water heater a big potential money saver down the road.
| Reliability |
| -Leak Detection System -Hot Start Programming Reduces Cold Bursts |
| Efficiency |
| -Condensing Technology -Water Saving Setting -Low-flow activation of 0.26 GPM -UEF of 0.90 |
| Warranty |
| -15-year heat exchanger warranty -5-year parts warranty |
| Overall Value |
| Fantastic water-saving and convenience features at a competitive price. |
Sometimes, you need hot water for a distant fixture. Whether it’s an outdoor bar, remote handwashing station, or basement kitchen, it would take too long for hot water to reach there from a central hot water heater.
That’s why I recommend the Eemax SPEX2412 electric point-of-use water heater. Built compactly, the SPEX2412 will blend into its surroundings. It can be mounted in any orientation and easily installed under a sink, in a closet, or in any ADA-compliant facility.
It has a low flow activation of 0.25 GPM, which is perfect for fixtures where you need just a little hot water. For example, I like to save water while washing the dishes by reducing the flow of water. Another water heater might not kick on if the flow was too low, so I’d be washing in cold water. Not so with this Eemax. Get hot water on demand when you need it.
The SPEX2412 comes with a five-year limited warranty on leaks and one year on parts. Overall, this nifty little unit will spoil you with hot water, and you’ll forget how you ever lived without it.
| Reliability |
| -Self-Diagnostics Protect the Unit |
| Efficiency |
| -Low-flow activation of 0.25 GPM -Compact Design Saves Space -Mounts in Any Orientation |
| Warranty |
| -5-year warranty on leaks -1-year parts warranty |
| Overall Value |
| Stellar price for on-demand hot water at the fixture. |
Commercial water heating applications require reliability and redundancy, both found abundantly in the Noritz NCC199CDV tankless water heater.
Link up to 24 units together for the most demanding applications. The modulating units all communicate to efficiently adjust the burner level as needed. The load is balanced between them to extend overall system life. You can also common vent up to six units without needing extra accessories thanks to a built-in exhaust non-return valve.
On the individual level, this rugged water heater has two stainless steel heat exchangers that will last years. Built-in safety devices protect against overheating, freezing, and other threats. Plus, with a 0.96 Uniform Energy Factor, the NCC199 is a high-efficiency leader.
These units can be installed outdoors or indoors using direct venting. They include a 10-year limited heat exchanger warranty for commercial use and a five-year limited parts warranty. Ultimately, you can count on the NCC199 for the most demanding hot water applications, like commercial kitchens and housing complexes.
| Reliability |
| -Links with Up to 24 Units -Built-in Safety Devices -2 Stainless Steel Heat Exchangers |
| Efficiency |
| -Condensing Technology -Modulating Burner -UEF of 0.96 -Common Vents with Up to 5 Other Heaters |
| Warranty |
| -10-year Heat Exchanger Warranty -5-Year Parts Warranty |
| Overall Value |
| A powerhouse for applications with the highest hot water demands. |
When selecting the best tankless water heaters, we consider four main criteria: reliability, efficiency, warranty, and overall value.
We focus on how reliably tankless water heaters supply hot water for showers, dishes, clothes, and other basic needs. There's no room for error. If you're a contractor, same thing. You want to sell your clients a water heater that will work right the first time and minimize callbacks.
We consider construction, design, performance, maintenance, longevity, and other characteristics that impact reliability. For example, what is the heat exchanger made of? Is installation straightforward? Do you have to perform annual maintenance?
The best tankless water heaters do their job silently in the background without you having to think about them too often. You should be able to trust them.
Efficiency, or how much energy the tankless water heater puts out versus how much it uses, is another consideration. The Uniform Energy Factor (UEF) measures water heater efficiency, with higher numbers being more efficient.
Whenever possible, we recommend condensing tankless water heaters. These are the most efficient models because they use a secondary heat exchanger to capture extra heat from the exhaust. The less heat wasted through the exhaust, the more being used to heat your water, which is what we want.
Another aspect of efficiency is whether a tankless water heater has built-in recirculation, which keeps hot water circulating in your pipes. That way, when you turn the faucet, you don't have to wait for the water to turn hot. This can save several gallons of water per day.
We expect tankless water heater makers to offer a good warranty in case anything goes awry. After all, tankless water heaters are an investment in your home and hygiene, so they need to stand the test of time. Typically, manufacturers include a warranty for the heat exchanger and parts, so that's what we look at when evaluating.
Although we do consider the price point in our best tankless water heater recommendations, it takes a back seat to overall value. The old phrase, "you get what you pay for" rings true.
Sure, you could choose the cheapest option, but what happens when it stops working after a year? Then, instead of spending a couple hundred extra dollars, you're spending more than a thousand on a new unit. Great quality at a good price is what we're after.
A tankless water heater works by heating cold water instantaneously as it passes through the system. Gas tankless water heaters use heat exchangers, while electric and point-of-use tankless water heaters use heating elements.
Unlike a traditional storage-tank water heater, which regularly heats water in a large tank whether it's needed or not, a tankless water heater activates only when someone turns the hot water faucet. As a result, tankless water heaters are more efficient and much smaller since they don't require a tank.
They also cannot run out of hot water as long as they're properly sized, since they only heat as needed. Tankless water heaters require a significant amount of energy to rapidly heat water. As a result, you may need to upgrade your gas line or increase your electrical power supply.
Learn more in our tankless water heater buyer's guide.
Properly sizing a tankless water heater is crucial to ensure it can handle all your hot water needs instantaneously. If you buy an undersized heater, it won't be able to keep up with your needs, and you'll be dealing with cold showers!
To size a tankless water heater, you need to determine 1) the flow rate of all the hot water fixtures you'll plan to run at once and 2) the required water temperature rise in your area. Water temperature rise refers to how many degrees the water heater will need to raise the incoming water temperature. Once you have those pieces of information, you can use our free tankless water heater sizing tool to find recommended products.
Yes, you can replace your old water heater with a tankless water heater. If you're replacing a tankless unit with a new tankless unit, it should be a clean swap. However, if you're replacing a storage-tank water heater with a tankless unit, there are a few extra considerations, particularly with gas-powered units.
Most storage-tank water heaters have plumbing connections on top, while many tankless units have them on the bottom. Switching may require extra material costs for your installer because they'll need to add plumbing to your existing setup.
Another consideration is the greater energy required by tankless water heaters to heat water on demand. If you have a gas model, you may need to make your gas line bigger. If you have an electric model, you might need to upgrade your panel or service. Be sure to discuss these and any additional requirements with your professional installer, and never attempt the installation yourself.
A tankless water heater should last 20 years or more when properly maintained. Proper maintenance includes periodic inspections and descaling, which is the removal of limescale deposits caused by hard water. Some units, like the A.O. Smith X3, are able to prevent scale from forming and eliminate the need for this kind of maintenance.
Ken DeJong has been a versatile handyman for decades, able to adapt to every home improvement challenge thrown his way. From working on cars in his youth, to installing carpet, and even doing decorative painting, Ken is a determined jack-of-all-trades. He served as a manager at Lowes before joining the Power Equipment Direct team.
Ken has amassed a wealth of product knowledge across various categories, especially when it comes to heating and cooling equipment. He has taken roughly 130 hours of professional training hosted by industry vendors and now trains others in his department. He’s particularly fascinated by ductless mini splits and the inverter technology that makes them exceptionally quiet and efficient.
When he's not helping customers choose the right evaporator coil or tankless water heater, Ken puts his creativity to use designing t-shirts and writing royalty-free instrumental music. To sum up, Ken is a professional who is obsessed with acquiring new skills and sharing his knowledge to help others optimize their home living.