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Jan 19, 2024

The 9 Best Tankless Water Heaters of 2023

Save energy and get hot water on demand with these tankless water heaters. Jump

Save energy and get hot water on demand with these tankless water heaters.

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Better Homes & Gardens / Taylor Tieden

Tankless water heaters provide hot water on demand, wherever and whenever you need it. They run on gas or electricity, provide higher energy efficiency, have a longer lifespan, and are more compact than tank models, which makes them optimal for use in smaller spaces. Since tankless water heaters only heat water as necessary, they eliminate standby energy losses, too.

"Regular water heaters store and constantly heat a large volume of water in a tank, making hot water readily available but less energy efficient," says Andrew Miles, a New York City Licensed Master Plumber at WaterFilterCast. "Tankless would be best for smaller families that don't have high hot water demands or don't need to use multiple outlets of hot water at the same time." If you’re stuck between choosing a tankless or regular water heater, Miles explains, "Tankless units will have a lower flow rate, so selecting one over the other mainly comes down to that."

Before you start shopping, add up the flow rate, or GPM (gallons per minute), of the fixtures you expect to be running at the same time, such as your shower and your washing machine, to determine if a tankless water heater will work for your household. If it does, there are several factors to keep in mind to find the best tankless water heater for your home.

"Consider fuel type first (natural gas, propane, or electric), size, and capacity based on your household's hot water needs," Miles says. "Other main considerations are features such as temperature control and modulating burners for optimal performance."

Amazon

It has an impressive flow rate and comes with a limited lifetime warranty.

It doesn't include WiFi integration.

As our top pick for the best tankless water heater, the EcoSmart ECO 27 is an extremely easy-to-use water heating option that can reduce your home's electrical load and save you money on your electric bill. It's easy to set up, too. The water heater has a flow rate of 5.27 GPM and enough power to instantly heat water for the average medium-sized family while keeping water consistently hot. To save energy, the 27,000-watt device features a patented self-modulating technology that adjusts the energy consumed based on your personal hot water needs.

There's a sensor (instead of a flow switch) that will detect a drop in water pressure so you won't be doused with cold water while it's heating up (known as the "cold water sandwich" that's common in many tankless water heaters). The temperature of this electric tankless heater goes from 80°F to 140°F, and there's an intuitive digital thermostatic temperature control that allows you to set it in single-degree increments. While the water will not get as hot as some other tankless water heaters, it still provides a more-than-adequate water temperature for showering and cleaning needs.

Designed for point-of-use installation, the unit is compact and doesn't take up much space. In addition, at just 14 pounds, it's lightweight, too. For installation, this indoor heater is designed to be used with 3 x 40 AMP double pole breakers. If you don't know a local plumber (and don't want to install it yourself), The Home Depot offers same-day installation services that you can select when you check out. This product also includes a limited lifetime warranty. While WiFi integration would make this unit even better, it's still a great mid-range tankless water heater that is reliable, does its job well, and won't break the bank.

Price at time of publish: $599

Product Details: Type: Electric, indoor | Dimensions: 17 x 3.7 x 17 inches | Flow Rate: 5.27 GPM | Total BTU: N/A | Watts: 27,000

Amazon

Its compact size is ideal for tight spaces.

It's not suited for colder climates.

With its low wattage and small size, the EcoSmart ECO 11 Electric Tankless Water Heater is our top pick for the best tankless water heater for anyone on a budget. It's ideal for smaller families of two or three, and it's only 11.5 inches in height, making it a great point-of-use water heater for inside a cabinet where it can be out of sight, too. It also only weighs 6.5 pounds, which helps when it comes to installation.

Designed to provide continuous hot water from 2.1 to 3.1 gallons per minute—just what's needed for a shower or bathroom and kitchen sink—this small electric water heater is easy to use with only a single knob controlling the temperature. The water can reach 140°F, however, this will be lower in much colder climates. The temperature can be changed, if need be, in one-degree increments by simply turning the controller. The temperature is also clearly visible on the easy-to-read LED display.

The unit's heat exchanger is made from durable stainless steel, and there's thermal auto reset technology for safety. The water heater's small size makes it a good option to install indoors in a summer house, condo, small business office, or shop. Just like its larger sister model (the EcoSmart ECO 27), the EcoSmart ECO 11 sports self-modulating technology that automatically adjusts how much energy is needed based on your hot water needs. It's also backed by the company's limited lifetime warranty.

Price at time of publish: $299

Product Details: Type: Electric, indoor | Dimensions: 11.5 x 8 x 3.7 inches | Flow Rate: Up to 3.1 GPM | Total BTU: N/A | Watts: 13,000

Amazon

It comes with a 15-year warranty and is super quiet, too.

You’ll need a 0.75-inch gas line for sufficient gas supply.

Rinnai's RU199iN model tops our list for the best tankless water heater in the condensing category. Although it's quite pricey, it has a high flow rate of up to 11 GPM for running multiple fixtures and appliances at once and a powerful 199,000 BTU. Extremely quiet at just 48 decibels, this natural gas unit is great for point-of-use installation as you’ll hardly hear it, even if it's in your en suite bathroom. A good condensing tankless water heater is great for anyone who would like the convenience of an eco-friendly unit with a higher flow rate, and this model ticks those boxes.

The Rinnai unit has high-efficiency ratings of up to 0.96 UEF (Uniform Energy Factor rating—a measure of energy efficiency; the higher the UEF, the more efficient the unit) and can be used with more cost-effective venting materials, such as polypropylene or PVC. The downsides are that the cost is typically higher up-front, and the unit also requires a drain and a 0.75-inch gas line, which may limit your installation options.

That being said, this unit from Rinnai is energy efficient as it only heats water when it's needed, and it comes with built-in recirculation technology that can make use of unused hot water for even more energy conservation (though you’ll need to buy an external pump for this separately). It comes with an impressive 15-year warranty and is only around the size of a suitcase. There are plenty of places to install it indoors, but calling in a pro to set it up is recommended.

Price at time of publish: $1,855

Product Details: Type: Natural gas, indoor | Dimensions: 33.86 x 22.05 x 14.76 inches | Flow Rate: Up to 11 GPM | Total BTU: 199,000 | Watts: N/A

The Home Depot

This unit offers vent-free installation, has an impressive temperature range, and includes a five-year warranty.

This type of unit (non-condensing) is less energy-efficient than a condensing unit.

With an excellent flow rate of 7.03 GPM that can support many fixtures, including a couple of sinks and up to five showers at the same time, the space-saving Rheem RETEX-36 is our top selection for the best non-condensing tankless water heater. This unit can easily serve as a home's whole-house water heater. The Rheem unit has an impressive temperature range and can be set to up to 140°F, but the Consumer Product Safety Commission and most professionals recommend setting the maximum temperature at or below 120°F to prevent burns.

This electric non-condensing heater doesn't require venting or a drain for installation, so there's a little more flexibility as to where it can be installed. However, keep in mind that these units aren't typically as energy-efficient as condensing models. They are, on the other hand, usually smaller and very low maintenance. The manufacturer states that using the Rheem RETEX-36 as your whole-house heater can save up to 34% in energy costs and up to 50% savings when used as a point-of-use heater.

Its small size of just over 18 inches in height and almost 22 inches in width, with a minimal 3.5-inch depth, means it can seamlessly blend in wherever you decide to install it. The water's temperature can be set in one-degree increments, and there's a five-year limited warranty on the heat exchanger, with a one-year limited warranty on parts. Though it's fairly straightforward to install in your home, the manufacturer still recommends calling in a professional to be on the safe side.

Price at time of publish: $649

Product Details: Type: Electric, indoor | Dimensions: 18.2 x 3.5 x 21.6 inches | Flow Rate: 7.03 GPM | Total BTU: N/A | Watts: 36,000

Amazon

It's energy-efficient, cost-effective, and comes with a remote thermostat.

It can be prone to the cold water sandwich while it's heating up.

With advanced technology and features, the Noritz NRC661 DV is one of the best natural gas tankless water heaters you can buy for an endless hot water supply, especially if you’re looking for a condensing unit in particular. In contrast to non-condensing units, condensing tankless water heaters capture and reuse heat from exhaust gasses, resulting in higher energy efficiency and lower operating costs.

This unit from Noritz comes with a good flow rate of 6.6 GPM, a powerful 120,000 BTU output, a remote thermostat, and a built-in controller. It has a small footprint and can support several faucets and showers at once, so it can easily be used as a whole-house water heater. The heater needs a 110V outlet to work, and the installation and operating instructions are thorough and easy to follow. Keep in mind that this indoor unit can be prone to a cold water sandwich while it's heating up.

The unit is highly efficient, extremely quiet (emitting only a gentle fan-like hum that can't be heard unless you’re right next to it), and has a consistent, digitally-regulated output temperature that's easy to adjust by one degree at a time. It's sturdy with a precision-engineered design, and the company backs its product with a 12-year warranty on the heat exchanger—a testament to its confidence in the product. It also comes with a five-year warranty on parts and a one-year labor warranty.

Price at time of publish: $1,586

Product Details: Type: Natural gas, indoor | Dimensions: 23.6 x 6.7 x 13.8 inches | Flow Rate: 6.6 GPM | Total BTU: 120,000 | Watts: N/A

Amazon

It's an affordable and easy-to-use, point-of-unit water heater that's a breeze to install.

It's only designed for use with one or two faucets.

While the Bosch Electric Mini-Tank Water Heater Tronic 3000 T isn't exactly a tankless water heater, it might as well be as it has all the perks of one. Deserving of a spot on our list of the best tankless water heaters, this hybrid unit is only 13.75 inches square and can be placed indoors anywhere at point-of-use, including on a shelf, the floor, a wall (the mounting bracket is included), or even in a small, organized under-sink cabinet. It's easy to install and highly affordable, too.

There are two versions available—this 2.5-gallon model or a slightly more expensive 4-gallon unit at the same size—both with high thermal efficiency designed to keep costs down. This little electric unit is far from a whole-house water heater, but it's great for use at a single sink or for supplying a condo, RV, or summer house with hot water. There's a built-in temperature release valve to increase safety, and it can supply hot water for up to two sinks at a time.

A single knob serves as the thermostat, and the unit easily connects to a cold water line with the included hardware. This Bosch Tronic 3000 T is an excellent option for supplementing an existing water heater, too. It's easy to maintain and won't need servicing for a long time as it's made with durable materials, including a glass lining and foam insulation. Its minimal white cuboid design means it's not an eyesore, even if it is unavoidably on display.

Price at time of publish: $206

Product Details: Type: Electric, indoor | Dimensions: 13.75 x 13.75 x 10.75 inches | Flow Rate: 2.5 GPM | Total BTU: N/A | Watts: 1,440

Amazon

It's compatible with installation in small spaces and can be monitored remotely since it's WiFi compatible.

The WiFi module has to be purchased separately.

Considering its impressive capabilities, such as a high 7.5 GPM flow rate and 180,000 BTU, the Rinnai RL75iN High-Efficiency Plus natural gas non-condensing tankless heater is a fairly compact model at just 31 inches in height. You can install it practically anywhere indoors, and it's powerful enough to provide hot water to several fixtures at a time. While this particular model is made for use with natural gas, there is also a very similar propane option available.

This is a reliable tankless water heater, and although it's not exactly cheap, it does come with an impressive 12-year warranty for extra peace of mind. Since it's quite a complex model, it's best to include professional installation.

One of the best things about this unit is its WiFi compatibility, which will require a separate purchase of the Control-R Wi-Fi Module. Miles recommends WiFi-compatible tankless water heaters, saying they include several perks if you don't mind spending a little extra.

"One nice feature found these days on newer models is that they can be connected to WiFi, allowing homeowners to monitor and control their water heater remotely using a smartphone app," Miles says. "This is a great way to optimize energy usage, troubleshoot issues, and even alert homeowners when something is going wrong with the unit." What's more, there's even a hot water recirculation ability (again, you’ll need to buy this accessory separately) that can circulate the water in the pipes back to the water heater and reheat it.

Price at time of publish: $1,255

Product Details: Type: Natural gas, indoor | Dimensions: 31 x 17.5 x 13 inches | Flow Rate: 7.5 GPM | Total BTU: 180,000 | Watts: N/A

Amazon

It's energy efficient, has a steady temperature output, and is super quiet, too.

You’ll likely need an electrician to install it (or to consult with one before buying) since it needs a 300-amp electric service, which is not compatible with all houses.

As one of the most energy-saving tankless water heaters on our list, the Stiebel Eltron Tempra 36 Plus won't ever use more electricity than you need it to while heating water, and since it has a minimum heating setting of 68°F, it won't allow the water to surprisingly scald you when you’re just trying to quickly wash your hands.

This clever little electric unit (it's only 14.5 inches tall) is very quiet and has a flow rate of up to 7.5 GPM and 36,000 watts. This model also has a technology that will slightly reduce the water flow when hot water is in high usage so that you won't be shocked by the cold water sandwich while it's trying to keep up with the hot water demand. The temperature can be set with the intuitive buttons and control knob, and there's also a temperature memory setting. Its automatic modulation helps save you even more energy, and the digital display will always let you know the temperature.

No venting is required with this non-condensing unit, and there's also an Advanced Flow Control to maintain a consistent temperature output. This is another indoor unit on our best tankless water heaters list that has a simple, minimal design, and though it's compact enough to be hidden away, it won't be unsightly if visible.

You’ll want to call in an electrician to install this unit as it requires 300 amps, which may require an upgrade to your electrical service panel. It comes with a seven-year warranty in the event of any leaks and a three-year warranty on parts.

Price at time of publish: $849

Product Details: Type: Electric, indoor | Dimensions: 14.5 x 4.63 x 16.63 inches | Flow Rate: Up to 7.5 GPM | Total BTU: N/A | Watts: 36,000

Home Depot

It's a highly efficient unit and has freeze protection down to -30°F.

The recirculation pump kit must be purchased separately.

Making it a standout pick, the Rheem Mid-Efficiency model is one of the only outdoor tankless water heaters available in this price range—and it's a good one. With a flow rate of 8.4 GPM, and 180,000 BTU of power, hot water is always available whenever you need it in the range of 85°F to 140°F. This natural gas heater provides enough hot water for constant use throughout the day to several faucets and showers simultaneously, making it entirely suitable for whole-house use.

With its weather-proof stainless steel construction, this unit was designed for outdoor use, meaning that you don't need to worry about venting. It's also safe in cold temperatures as there's freeze protection down to -30°F. The temperature of the water is easily adjustable in two-degree increments via the electronic thermostat, and there's a simple on-off button, so you can save energy by switching it off entirely when you’re away. For further energy efficiency, you can opt to purchase and add the extra recirculation pump kit.

In addition, cold bursts are minimized thanks to the unit's Hot Start Programming, which stays in ready-fire mode. The digital display is clearly visible and shows the water temperature as well as any diagnostics that let you know when the unit is due for service. Professional installation is recommended, and since the unit is rather heavy (54 pounds), two people will likely be required to set it up. It measures 23.63 x 13.88 x 8.88 inches, so make sure you have enough outdoor space to accommodate it.

Price at time of publish: $953

Product Details: Type: Natural gas, outdoor | Dimensions: 23.63 x 13.88 x 8.88 inches | Flow Rate: 8.4 GPM | Total BTU: 180,000 | Watts: N/A

The easy-to-use and install EcoSmart ECO 27 is our top choice for the best tankless water heater because it has a good flow rate and powerful 27,000-watt electric operation. It also provides you with consistent and constant hot water up to 140°F, and it's a great value for the price, featuring self-modulating technology for additional energy and cost savings.

If you’re on the fence about which type of water heater to choose, keep in mind that tankless water heaters are much smaller than standard water heaters with tanks. Sizes vary from 10 to 35 inches in height and 8 to 25 inches in width. When installing a tankless water heater, Miles advises first measuring the space where the tankless heater will go and then shopping for units that will fit inside that designated space, making sure to leave some free space around it. "This will make the installation go easier by not having to work in too tight of a space," he says.

The flow rate of a water heater is measured in gallons per minute (GPM). Compared to regular water heaters with tanks, the flow rate of tankless water heaters is lower. Flow rates range from around 2.5 GPM for smaller units, with much larger units reaching up to 11 GPM.

"Homeowners should consider their daily routines and think of the devices and appliances that might be used simultaneously, such as taking a shower while the washing machine is running," Miles says. "For example, a heater with a flow rate of at least 4.5 GPM would be needed to handle a 2.5 GPM showerhead and a 2 GPM washing machine."

For gas water heaters, a general total BTU rating (this stands for "British thermal unit" and is a measure of the heat content of a unit's energy source) is provided, whereas the power of electric tankless water heaters is measured in watts. Electric tankless water heaters for residential use can be rated anywhere from 1,000 to 36,000 watts.

Gas tankless water heaters typically range from around 100,000 to 200,000 BTU. "A general guideline is 10,000–20,000 BTU for every 1 GPM of flow rate," Miles advises. "A higher BTU rating results in a faster temperature rise but consumes more fuel typically, so you need to balance energy efficiency and performance based on the specific hot water requirements."

When it comes to installing your tankless water heater, the key steps are to first measure the space where you want to mount the new unit to ensure the model you want can fit comfortably with some space around it. The next steps, according to Miles, are connecting the gas or electrical, the main water line, and any other electrical lines. "If you use gas, then also add in venting, and finally, testing the unit for leaks and proper operation," he says.

Tankless water heaters can cost anywhere from $300 to $3,000, with prices varying depending on factors such as fuel type, capacity, brand, and any additional features. Based on our research, there are excellent models right in the middle of that range, around the $1,000 mark.

"You can find electric and propane units in the $500 to $2,500 range, while gas-powered units can cost between $750 and $3,000," Miles says. "The total cost, including installation, can range from $1,500 to $4,500 or more, depending on the specific circumstances and requirements."

"The only way a tankless heater would run out of water is if multiple fixtures are used at the same time, depleting the reserve before it can heat new water coming in," Miles says. "One of the main benefits of tankless water heaters is that they provide a continuous supply of hot water as long as the demand doesn't exceed the unit's flow rate capacity."

This article was written by Kat de Naoum, who has over 10 years of commerce writing experience. Kat is also the commerce editor-at-large at Thomas-Xometry, the leading U.S. online platform for supplier discovery and product sourcing. For this article, Kat reviewed multiple tankless water heaters, researching factors such as each water heater's dimensions, flow rate, and total BTU. She also spoke to Andrew Miles, an NYC Licensed Master Plumber at WaterFilterCast.