8 High-Quality Whole-House Tankless Water Heaters (Find the Best High Performer)

Since we know different consumers have different needs, we wanted to make sure to include both point-of-use and whole-house tankless water heaters in our research and reviews. We’ve scoured a variety of manufacturers and come up with a pretty inclusive list of the best whole-house tankless water heaters for you to choose from.

For a whole-house tankless water heater to be considered a good purchase, it must have enough capacity for a variety of homes. We’ve included different sizes for those looking for smaller tankless water heaters that will still be powerful enough to heat water for an entire home, as well as those that will easily handle multiple showers for busy households.

We truly hope you find unique value in our comparison of whole-house tankless water heaters that we have put together. Always be sure to visit the manufacturer’s website or call customer service for specific sizing information for your water temperature rise and your household size. Read on for our list of the best eight tankless water heaters for an entire home.

  • 4 Customer Rating
  • EcoSmart ECO 27
  • Dimensions: 3.6 x 17 x 17 inches
  • Flow Rate: 3 GPM
  • Power Source: Electric-Powered
  • Weight: 16.8 pounds
  • Made In: USA
  • Warranty: Lifetime Warranty
  • 4.5 Customer Rating
  • Stiebel Eltron Tempra Plus 29
  • Dimensions: 22.4 x 12 x 20.1 inches
  • Flow Rate: 2.8 GPM
  • Power Source: Electric-Powered
  • Weight: 19 pounds
  • Made In: USA
  • Warranty: 7 years leakage/ 3 years parts
  • 4.5 Customer Rating
  • Stiebel Eltron 224199
  • Dimensions: 21.7 x 20.1 x 9.6 inches
  • Flow Rate: 0.37 GPM
  • Power Source: Electric-Powered
  • Weight: 16.1 pounds
  • Made In: USA
  • Warranty: 7 years leakage/ 3 years parts
  • 4.5 Customer Rating
  • Rheem RTGH-95XLN
  • Dimensions: 18.5 x 9.8 x 27.5 inches
  • Flow Rate: .40 GPM
  • Power Source: Gas-Powered
  • Weight: 78.3 pounds
  • Made In: USA
  • Warranty: Manufacturers
  • 4.5 Customer Rating
  • Stiebel Eltron 224196
  • Dimensions: 19.5 x 21.5 x 8.5 inches
  • Flow Rate: 0.37 - 3.0 GPM
  • Power Source: Electric-Powered
  • Weight: 13.5 pounds
  • Made In: USA
  • Warranty: 7 years leakage/ 3 years parts
  • 4.5 Customer Rating
  • Stiebel Eltron Tempra 20 Plus
  • Dimensions: 19.5 x 21.5 x 8.5 inches
  • Flow Rate: 0.58 - 4.5 GPM
  • Power Source: Electric-Powered
  • Weight: 16.1 pounds
  • Made In: USA
  • Warranty: 7 years leakage/ 3 years parts

EcoSmart ECO 27 Electric Tankless Water Heater

To make certain your home is a good fit for the ECO 27, check your electrical panel and be sure it is at least 200 amps. Next, you’ll need three 40-amp double poles available inside for the hard wiring. This EcoSmart ECO 27 has a max draw of 27 kilowatts at 240 volts, so it will use quite a bit of electricity when it is in use. The best part about this tankless water heater, though, is that the ECO 27 will shut off when there are no hot water demands in the house. This good tankless water heater falls in the middle of the price range for tankless water heaters, and would be a nice fit for a mid-sized home with average hot water needs.

At just 17″ H x 17″ W x 3.5″ D, you will not only save anywhere from 50-60% on your hot water heating portion of the bill, you’ll also save ample space in your utility area. With a GPM ranging from 2.6 to 6.5, this ECO 27 will power one shower and two faucets in cold climates at a low GPM flow rate, or four showers and a faucet in the warmest climates with a higher GPM flow rate. Customers are very happy with the customer service support from the team at EcoSmart—technicians are easily available to help with sizing, installation, and maintenance questions. EcoSmart offers a lifetime warranty on the electronics, the stainless steel exchanger, and the heating element. That warranty will go a long way for some customers!

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Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater

These Stiebel Eltron whole-house tankless water heaters are made in Germany. They have a special feature for busy households that demand a high amount of hot water called Advanced Flow Control. Instead of allowing a shower or washing machine to go cold, the technology will reduce the water pressure flow at the taps so that the hot water is maintained. Basically, the regulator limits the amount of cold water that comes through the input pipe when there are high hot water demands.

The best application for the Tempra 29 Plus unit will be homes or condo units with 2 or 3 bathrooms. This is Stiebel Eltron’s second largest tankless water heater. The 29 Plus will require a minimum 200 amp electric service, and draws 120 amps during use. It is a 240 volt, 28.8 kW appliance. The gallons per minute (GPM) will depend on the necessary temperature rise of your water, but should range from 2.5 at a 90-degree temperature rise, to 8.0 on a 25-degree temperature rise.

For those looking for a good whole-house tankless water heater, this would fit well because of its ease of installation and mid-high price point. Since it’s an electric unit, you won’t need to worry about any venting or gas line hookup. Make sure your electrical panel has the required breaker spots as detailed in the manual.

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Stiebel Eltron Tempra 24 Plus Electric Tankless Water Heater

Rest assured, if you are willing to break away from traditional tank water heaters and try an electric tankless for your whole home, you simply will not be disappointed with the Tempra 24 Plus from Stiebel Eltron. This unit would be good for a small family in a mid-size home with a medium budget. You can expect to save anywhere from 15 to 20% on the hot water portion of your electric bill. Based on your usage habits, your savings could be even higher. The digital temperature controls on the Tempra 24 Plus are foolproof and let you set the temperature to your exact liking. You will always know the exact temperature the unit is set to—and it is easy to see if it has been changed or tampered with. With Tempra’s technology, the Tempra 24 Plus maintains a consistent hot water temperature, no matter the demand or length of water use.

For this unit, you can expect to run either two showers or one shower and one washing machine at the same time. The GPM can range from 1.5 to 4.5, based on the demand. At just over 15 pounds and 21.5 x 19.5 x 8.8 inches, this tankless water heater takes up much less space than traditional water heater tanks. The Tempra 24 Plus does require a minimum circuit breaker space of a double pole 2 x 60. While the unit is reasonably priced, if you are considering purchasing this model, please be sure to factor in the cost of installation by a professional and/or any electrical work or upgrades that might need to be done. For your convenience, the Tempra 24 Plus does come with a three-year limited warranty (but the product must be installed by licensed personnel).

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Rheem RTGH-95XLN Natural Gas Outdoor Condensing Tankless Water Heater

The RTGH-95XLN is one of the most efficient Rheem tankless water heaters, with an energy factor (EF) of 0.94. This EF also means the RTGH-95XLN is Energy Star qualified. Because it’s a condensing unit, it has a stainless steel heat exchanger, versus most other units that use a copper exchanger. You’re definitely getting a great GPM flow rate with this unit at 9.5. All of these factors place this model at the top of the price range.

It does have a two-pipe direct vent system designed for PVC pipe, for up to 35 feet of 3-foot PVC pipe or 5 feet of 2-foot PVC pipe. The RTGH-95XLN requires an installer to hard-wire an electrical connection for the starter, as there’s no pilot light.

Rheem also boasts about their 0.26 GPM minimum flow rate — claiming that to be the best in the industry — and a 0.40 GPM minimum activation flow rate. This is great for customers who sometimes want a light hot water stream for washing dishes or hands. Rheem’s water heaters include a 12-year limited heat exchanger warranty, and a five-year limited parts warranty.

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Stiebel Eltron Tempra 12 Plus Electric Tankless Water Heater

Surely you know that if you’re going with an electric whole-house tankless water heater, you’re likely to pay less than comparable gas units. What you might not know is that the Stiebel Eltron Tempra 12 Plus is designed to be virtually 100% efficient. That will significantly help on the water heating portion of your energy bill.

Now down to the details: The Tempra 12 Plus comes in the middle of the price range. While it is easy to install with no venting or gas line hookups like gas models, it does have some specific electrical requirements. If the unit is installed with 240-volt service, the Tempra 12 Plus would fit just right for a small home, condo unit, or apartment with one bathroom.

You should anticipate that the Tempra 12 Plus will draw 50 amps and it does require a minimum of 100-amp electric service. So, if you don’t want to do any modifications to your panel, and you’re short on space, this might squeeze into the breaker spots you have left.

The GPM should range (in cold northern climates) from about 1.0 to 1.5 with a 90-degree temperature rise, and up to 4.5 with a 20-degree temperature rise in warmer climates.

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Stiebel Eltron Tempra 20 Plus Electric Tankless Water Heater

Here we are with the Stiebel Eltron Tempra 20 Plus. You’ll see that this whole-house tankless water heater falls in the mid-high price range. But, if you have one bath in a cold northern climate or one or two in a warmer southern climate, this would be a fine fit for your condo or apartment.

These Stiebel Eltron whole-house tankless water heaters are made in Germany. All of the Tempra Plus versions have a special feature for busy households that demand a high amount of hot water called Advanced Flow Control. Instead of allowing a shower or washing machine to go cold, the technology will reduce the water pressure flow at the taps so that the hot water is maintained. In basic terms, the regulator limits the amount of cold water that comes through the input pipe when there are low hot water demands.

Electric whole-house tankless water heater users do really like the ease of use of the digital temperature control. Stiebel Eltron also offers a limited warranty of seven years against leakage, and three years against defects in workmanship and materials. Be sure to read through the warranty for specific details.

The Tempra 20 Plus draws 80 amps and requires a minimum of 125 amps of electric service. For 240-volt service, the Tempra 20 Plus uses 19.2 kW while operating.

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Bosch Tronic WH27 Electric Tankless Water Heater

Bosch has labeled this tankless water heater as a whole-home heater—but they also call out the fact that it is made to heat water for one major appliance at a time. If you have a small home with light hot water demands, or if your home has three or less occupants, this would be a good fit for you. Other possible applications would be an office unit with a small bathroom attached, an in-law suite, or a garage apartment. You will have to be adept at using just one hot water demand at a time—don’t run the dishwasher and the clothes washer at the same time, for instance, or you’ll just end up washing your dishes with cold water.

Due to its smaller capacity and its electric heat source, the Tronic WH27 is cheaper than even the low-end gas-powered models. For our electric models, it is right about in the middle of the price range. With a 55-degree temperature rise (common for warmer climates) you can expect a max of 3.3 GPM on your water flow. Bosch does achieve an impressive 97% efficiency on this model, so it is Energy-Star certified.

The Tronic WH27 is a 240-volt tankless water heater, and if lesser voltage is used, you will have reduced electric output ability in the heater. The WH27 requires 120 amps of electricity. For installation, 120 amps would be supplied through three 40-amp double-pole breakers in your breaker box, so check to make sure you have the space available. Your house must have at least 200-amp service, which older homes likely don’t have.

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Bosch Therm 520 HN NG Natural Gas Tankless Water Heater

This Therm 520 HN NG from Bosch is definitely one of a kind. Bosch is looking to attract a very specific customer with this whole-house tankless water heater. It is a non-condensing natural gas unit, with max BTUs of 117,000, and it’s made to be installed indoors. The real unique factor is in the ignition source—this unit uses no electricity or gas to start the heater. Instead, a water-powered turbine uses the water flow to ignite the burner.

This battery and electricity-free ignition means that this heater is the perfect fit for remote homes or spaces without access to electricity, or even areas with more rough or stormy weather and frequent power outages. Have a hunting cabin or rustic getaway tucked away from society? The Bosch Therm 520 HN NG would be a great fit for you. You will still need to have natural gas access to fuel the heater, but for the ignition itself, it’s powered without it.

A few of the little details: you’ll get an Energy Factor of 0.78 with this heater, and you can expect it to power 1-2 appliances or hot water taps at the same time. With a 35-degree temperature rise (for those in very warm climates, with an incoming water temperature of 70-80 degrees Fahrenheit or above), you can expect 5.2 GPM for your water flow. For a 55-degree rise, capacity would be at about 3.4 GPM. That patented technology from Bosch does push the Therm 520 HN NG’s price to the mid-high end of the natural gas line, but it’s still a fairly reasonably priced whole-home heater.

Summary

There simply ins’t just one best whole-house tankless water heater in the entire market. Each manufacturer has engineered a variety of its own technology to develop what it considers is the best product.

Once again, we must point out that one of the most important ways you can be sure you are extremely happy with your unit is to make sure you have the right size tankless water heater for your home. Many manufacturers will either give you a sizing guide online, or offer specific support by phone to make sure you are pleased. They also do not want you to be disappointed with your purchase, since it will be a significant investment for your home and your budget. Oftentimes users who do not do sufficient research will throw in the towel with tankless water heaters because they did not have the proper information to make the right choice for their home’s electrical capability or hot water demands.

Also, if you don’t have the correct electrical service and dedicated space in your panel, you will incur much more costs than you anticipated. It is unusual for the total cost of your unit to just include the purchase price of the parts. Most of the time, you cannot simply replace an old tank with a tankless unit without any electrical modifications or work.

Of course, you must consider your home’s unique needs before making your decision. We hope that you have found value in the information we have gathered on each listing as we try to make a good comparison of whole house tankless water heaters.