The 8 Best Tankless Water Heaters of 2021

Leverage these appliances when you're short on space

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Best Tankless Water Hea

The Spruce / Chloe Jeong

A tankless water heater saves space and offers greater energy efficiency than many conventional water heaters. Best of all, this type of water heater never runs out of hot water, since there is no storage tank to deplete! Instead, you'll enjoy warm water on demand for as long as you like—as long as you're working within its limitations.

Shop for a tankless water heater that matches your needs in terms of GPM of hot water. Think about periods of peak activity and determine how many water fixtures might be on at once, such as showers, washing machines, sinks, and dishwashers. Add up each fixture's GPM flow rate to determine peak water usage needs and look for a tankless water heater to match.

Here, the best tankless water heaters for you to consider. 

Our Top Picks
Its sophisticated Circ-Logic technology allows you to set recirculation patterns that heat water only when you need it.
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The compact design, easy maintenance, and overall reliability make this heater a great option for all sorts of needs.
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If you can make do with a lower GPM, this less expensive model might suit your needs without a big investment.
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Runner Up, Best Budget:
Bosch Tronic 3000 at Amazon
If space is tight, you can securely mount this mini tank heater on a wall, or inside a shelving unit or cabinet.
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Its built-in freeze, overheat, and surge protection means that you won't have to worry about burst pipes or any other accidents.
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Best for Small Homes:
Ecosmart ECO 11 at Amazon
Able to heat up to two gallons of water per minute (enough for two sinks and one shower), this heater is well suited for smaller homes.
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Designed especially for outdoor installation, this heater is built to quickly heat water in spaces that lack climate control.
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This portable outdoor unit is perfect if you need hot water for showers, cooking, and handwashing on the go.
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Best Overall, Natural Gas: Rinnai RL Series HE+ Tankless Hot Water Heater

Rinnai RL Series HE+ Tankless Hot Water Heater

A natural gas tankless water heater is an efficient way to have a ready-supply of hot water on demand. The Rinnai RL series of tankless water heaters offers a great combination of value and efficiency. Natural gas tankless water heaters generally offer faster flow rates than electric and are a good option if you already had a gas water heater previously installed. Japanese-maker Rianni is known for producing reliable and powerful tankless water heaters that won’t leave much to be desired when compared to your conventional tank water heater.

The Rinnai RL75i offers up 7.5 GPM of hot water and can support up to four different fixtures at once, depending on the incoming groundwater temperature. Even if you live in a cold weather climate, this gas-fired tankless water heater can supply hot water to at least three fixtures if the water temperature is at least 57 degrees. This model is also equipped to take advantage of Rianni’s Circ-Logic recirculation technology, which optimizes the energy usage of the tank’s recirculation pump—though you need to purchase Rianni's pump kit and control-R module to take advantage of this feature.

Best Overall, Electric: Rheem Performance 7.03 GPM Tankless Electric Water Heater

Rheem Performance 36 kw Self-Modulating 7.03 GPM Tankless Electric Water Heater

If you’re replacing a conventional electric water heater, then it’s usually most simple (and cost-effective) to choose an electric tankless water heater. This 7 GPM model from Rheem is popular for its performance and easy operation. A digital temperature display makes it easy to see what temperature the unit is set to heat incoming water to, and you can adjust it by a single degree from 80 to 140 degrees using the knob.

While small in size, measuring just 18 inches tall by 21 inches long, most people don’t miss their large, bulky tank water heater. This electric water heater keeps up with hot water needs for the majority of households; it can supply hot water for up to five showers and two sinks simultaneously (depending on the groundwater temperature and your shower's flow rate). 

Best Budget: EcoSmart ECO 18 Tankless Electric Water Heater

EcoSmart ECO 18 Tankless Electric Water Heater

While tankless water heaters represent a larger upfront investment than the cost of a conventional water heater, the EcoSmart ECO 18 is a more affordable tankless model that closes the gap in price between tank and tankless water heaters. The ECO 18 heats more than 2.5 gallons per minute and can support up to two showers simultaneously in warm weather climates. It features digital controls to make it easy to set the target temperature for the water.

This budget tankless water heater offers electric operation and is easy to install in the place of an electric tank water heater. However, it’s small size and affordable price tag mean that it’s also somewhat more limited in capacity—it’s really only powerful enough to serve as a whole home tankless water heater in areas where the incoming water temperature is 62 degrees Fahrenheit or greater. 

Runner Up, Best Budget: Bosch Tronic 3000

Bosch Tronic 3000

A point-of-use tankless water heater is compact enough to fit under sinks and is commonly used to boost hot water availability in bathrooms or kitchens. It can be used to boost supply from a larger whole house tankless water heater or a conventional water heater that lies far from the sink’s location. This model from Bosch measures just 13.75 x 13.75 inches; it can easily be mounted on a wall, shelf, or cabinet floor.

While it’s only designed to support one sink, it delivers hot water on the spot and doesn’t waste energy heating and storing water for future use. In addition, it has an excellent 98 percent energy efficiency rating. 

Best Splurge: Takagi T-H3-DV-N Condensing Natural Gas Tankless Water Heater

Takagi T-H3-DV-N Condensing Natural Gas Tankless Water Heater

You’ll spend more for a condensing tankless water heater, but these models work extra hard to capture energy and improve efficiency. The Tagaki T-H3-DV-N model is capable of producing up to 10 GPM of hot water, and can supply up to four fixtures in warm weather and three fixtures if the source water temperatures are cooler. At the same time, this EnergyStar-certified natural gas tankless water heater saves energy by capturing heat from the exhaust produced using a secondary heat exchanger.

This 199,000 BTU tankless water heater from Tagaki, a Japanese water heater company, is known for producing a reliable flow of hot water for showers, appliances, and other household needs without skipping a beat. One thing to note is that it can be trickier to find a service technician who is experienced in troubleshooting or repairing this brand of water heater. 

While gas tankless water heaters have a higher initial cost than electric models, condensing versions like this one cost a premium price. However, they represent some of the most energy-efficient tankless water heaters on the market.

Best for Small Homes: Ecosmart ECO 11 Electric Tankless Water Heater


Small homes, with their lower hot water demands, often benefit from a tankless water heater. The EcoSmart ECO 11 is a great option if you really only need to run one or two water fixtures at a time, like a sink and a shower.

This model can heat up to 2 gallons of water per minute. If you live in a warm weather climate, this tankless water heater can meet the needs of most small homes by supplying hot, steamy water to a bathroom sink and a shower simultaneously. However, if you live in an area where the incoming water temperature sinks below 72 degrees, you’ll have to be choosier when turning on the hot water tap—this tankless water heater can only run a single shower or two sinks in colder weather. 

Best Outdoor: Rinnai V53DeN Outdoor Tankless Water Heater

Rianni V53DeN Outdoor 5.6 GPM Residential 120,000 BTU Natural Gas Tankless Water Heater

Most water heaters are tucked into utility closets or installed in basements, which makes sense since these appliances are more effective and efficient if they don’t have to also battle the drain of cold weather. This is especially true for tankless water heaters which have to do their work on the spot and deliver warm water right away to your shower, sink, or other appliance. However, the Rinnai Value Outdoor Natural Gas Tankless Water Heater is a 5.6 GPM model that is designed for outdoor installation and saves space inside your home.

This model from well-known water heater manufacturer Rinnai is built to withstand installation in spaces that lack climate control, like attached garages, attics, or crawlspaces. It can support up to two showers simultaneously.

Best Portable: CAMPLUX ENJOY OUTDOOR LIFE Outdoor Portable Propane Tankless Water Heater

Camplux Water Heater

If you want hot water on the go, consider a portable tankless water heater. This model from Camplux connects to a propane tank and offers up to 1.32 GPM of hot water for showers, cooking, and handwashing. With a battery-powered ignition and easy operation, it’s great for camping or other off-grid scenarios. The Camplux Portable Tankless Water Heater includes a gas regulator and showerhead for easy set-up. To effectively use this portable tankless water heater, just be sure that you have minimum water pressure of 3.0 PSI. 

Article Sources
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  1. U.S. Department of Energy, Office of Energy Saver. Tankless or Demand-Type Water Heaters.

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