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

Because we understand that people have unique needs, our goal is to include the best applications and water heaters within our comprehensive research and reviews. We have looked at the top manufacturers in the industry and developed a solid list that the average consumer can choose from.

A good tankless whole-house water heater should have the capacity to supply a variety of homes in order to be considered a solid investment. Included within this review is a variety of sizes for different applications of tankless water heaters, especially for smaller homes. They can accommodate multiple showers and powerful enough to heat hot water to run an entire house.

It’s our hope that you find some extraordinary value in our comparison and reviews. It’s always a good idea to call customer service or visit the manufacturer’s website for your household size, water temperature, and specific sizing. Below is our list of what we consider the best eight tankless water heaters that accommodate an entire home.

Comparison of the Top Tankless Water Heaters in the Market Today

Preview
Best Price
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
Stiebel Eltron 29 Plus Tempra, Tankless Water Heater, White
Best Choice
Stiebel Eltron 224199 240V, 1 Phase, 50/60 Hz, 24 kW Tempra 24 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Rheem RTGH-95XLN Prestige Natural Gas Outdoor Whole House Low NOx Condensing Tankless 9.5 GPM Water Heater
Stiebel Eltron 12 Plus Tempra, Tankless Water Heater, White
Stiebel Eltron 224198 240V, 1 Phase, 50/60 Hz, 20 kW Tempra 20 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Title
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
Stiebel Eltron 29 Plus Tempra, Tankless Water Heater, White
Stiebel Eltron 224199 240V, 1 Phase, 50/60 Hz, 24 kW Tempra 24 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Rheem RTGH-95XLN Prestige Natural Gas Outdoor Whole House Low NOx Condensing Tankless 9.5 GPM Water Heater
Stiebel Eltron 12 Plus Tempra, Tankless Water Heater, White
Stiebel Eltron 224198 240V, 1 Phase, 50/60 Hz, 20 kW Tempra 20 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Prime Benefits
-
-
Best Price
Preview
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
Title
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
Prime Benefits
Preview
Stiebel Eltron 29 Plus Tempra, Tankless Water Heater, White
Title
Stiebel Eltron 29 Plus Tempra, Tankless Water Heater, White
Prime Benefits
Best Choice
Preview
Stiebel Eltron 224199 240V, 1 Phase, 50/60 Hz, 24 kW Tempra 24 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Title
Stiebel Eltron 224199 240V, 1 Phase, 50/60 Hz, 24 kW Tempra 24 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Prime Benefits
-
Preview
Rheem RTGH-95XLN Prestige Natural Gas Outdoor Whole House Low NOx Condensing Tankless 9.5 GPM Water Heater
Title
Rheem RTGH-95XLN Prestige Natural Gas Outdoor Whole House Low NOx Condensing Tankless 9.5 GPM Water Heater
Prime Benefits
-
Preview
Stiebel Eltron 12 Plus Tempra, Tankless Water Heater, White
Title
Stiebel Eltron 12 Plus Tempra, Tankless Water Heater, White
Prime Benefits
Preview
Stiebel Eltron 224198 240V, 1 Phase, 50/60 Hz, 20 kW Tempra 20 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Title
Stiebel Eltron 224198 240V, 1 Phase, 50/60 Hz, 20 kW Tempra 20 Plus Whole House Tankless Electric Water Heater, Advanced Flow Control
Prime Benefits

 

Top 8 Whole-House Tankless Water Heaters Reviews


1. EcoSmart ECO 27 Electric Tankless Water Heater

Sale
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
  • Savings of up to 50% on water heating costs. Dimensions :17H x 17W x 3.625D inches ;Pipes fittings :3/4 inch NPT
  • Digital temperature control in 1-degree increments allows control of hot water; Activation Flow: 0.3 GPM
  • Flow Rate: 3 GPM
  • Dimensions: 3.6 x 17 x 17 inches
  • Weight: 16.8 pounds
  • Power Source: Electric-Powered
  • Warranty: Lifetime Warranty
  • Made In: USA

In order for the ECO 27 to fit your home, check your electrical panel to make sure it’s at least 200 amps. It also requires three 40 amp double poles inside for the hard wiring. The unit is designed with a max draw of 27 kW at 240 volts and uses its fair share of electrical power when in use. One of the best features of the EccoSmart ECO 27 is the automatic shut-off when not in use. This is a dependable tankless water heater that falls in the mid-price range and is a good fit for mid-sized homes with typical hot water needs.

It measures in at 17” (H) x 17” (W) x 3.5” (D), you will save both space in your installation area and about 50-60 percent on your hot water bill. It has a GPM range of 2.6 – 6.5, and the ECO 27 can power two faucets and one shower in cold environments with a low flow-rate, or one faucet and four showers in warm environments at a higher GPM flow-rate. EcoSmart has an outstanding customer service department with available technicians who can help you with installation, maintenance, and sizing questions. They offer a limited lifetime warranty on the heating element, stainless steel exchanger, and electronics. This is a warranty that really benefits the consumer in the long run.


2. Stiebel Eltron Tempra Electric 29 Plus Tankless Water Heater

Sale
Stiebel Eltron 29 Plus Tempra, Tankless Water Heater, White
  • On demand a continuous and unlimited supply of hot water
  • Sleek design saves space and no venting required
  • Flow Rate: 2.8 GPM
  • Dimensions: 22.4 x 12 x 20.1 inches
  • Weight: 19 pounds
  • Power Source: Electric-Powered
  • Warranty: 3-years parts/7-years leakage
  • Made In: Germany

The Stiebel Eltron is manufactured in Germany. One of the best features of the Tempra 29 is the Advanced Flow Control for hectic households that require a lot of hot water. Instead of allowing a washing machine or shower to go cold, the advanced technology reduces the water pressure at the taps and regulates the temperature. It works by limiting the amount of cold water that can access the input line when high demands for hot water are in use.

The Tempra 29 will work great in condos or homes with two to three bedrooms. This is the second largest tankless water heater manufactured by Stiebel Eltron. The Tempra 29 Plus draws 120 amps and requires a minimum of 200 amps for electrical service. This is a 28.8 kW and 240-volt appliance. The GPM will depend on the rise in temperature of your water; however, you can expect to get about 8.0 on a 25 degree in temperature rise and 2.5 on a 90-degree rise in temperature.

You won’t be disappointed with its price and ease of installation. Because this is an electric unit, there’s no need to worry about hooking up any gas lines or ventilation. Check your electrical service panel for available breaker spots as outlined in the owners manual.


3. Stiebel Eltron Tempra Electric 24 Plus Tankless Water Heater

  • Flow Rate: 0.37 GPM
  • Dimensions: 21.7 x 20.1 x 9.6 inches
  • Weight: 16.1 pounds
  • Power Source: Electric-Powered
  • Warranty: 3-years parts/7-years leakage
  • Made In: USA

If you want to break away from traditional water heater tanks and upgrade to an electric tankless in your home, the Tempra 24 Plus will not let you down. This is a great unit for mid-sized homes with a small family and where the budget is a concern. You can expect to save about 15 to 20 percent of your utility bill for hot water. Depending on usage, the saving could be even more significant. The Tempra 24 Plus utilizes digital temperature controls and allows the temperature to be programmed to your exact requirements. Another great feature is knowing exactly what the water temperature is, it will even tell you if someone has messed with it. Tempra’s technology provides a consistent hot water temperature, independent of the length or demand for water use.

This unit will supply one washing machine and up to two showers at the same time. The GPM ranges from 1.5 to 4.5, depending on the demand. It weighs in at just over 15 lbs and measures 21.5” (H) x 19.5” (D) x 8.8”(H), this unit uses less space than standard water heater tanks; however, it does require a double pole circuit breaker space of 2 x 60. Although this tankless water heater is affordable, before you make your purchase, consider the cost for hiring a professional installer/electrician to install the device or make any upgrades to your existing wiring applications. The Tempra 24 Plus, needs to be installed by a licensed technician in order for the limited three-year warranty to apply.


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

Rheem RTGH-95XLN Prestige Natural Gas Outdoor Whole House Low NOx Condensing Tankless 9.5 GPM Water Heater
  • .94 Energy Factor (EF) with efficient stainless steel condensing heat exchanger
  • 2-Pipe Direct Vent System designed for PVC Pipe
  • Flow Rate: 0.40 GPM
  • Dimensions: 18.5 x 9.6 x 27.5 inches
  • Weight: 78.3 pounds
  • Power Source: Gas-Powered
  • Warranty: Manufacturers
  • Made In: USA

The Rheem RTGH-95XLN is known for being Rheem’s most efficient tankless water heater. The RTGH-95XLN is an energy-star rated appliance and has an energy factor of 0.94. This device utilizes a stainless steel heat exchanger, and it’s also a condensing unit, unlike traditional units that utilize a copper exchanger. Considering all of its features, it’s clear why it’s rather expensive.

It’s designed for PVC piping with a two-pipe direct ventilation system, for up to five feet of two-foot PVC pipe or 35 feet of three-foot PVC pipe. This Rheem unit does require a licensed installer to hard-wire the starter because there’s no pilot light.

The RTGH-95XLN, claims to have the best GPM in the industry with a 0.26 minimum flow rate and 0.40 minimum activation flow rate, and it’s a great device for those who want a lighter hot water temperature for washing their hands and doing dishes. Rheem’s come with a five-year limited warranty on the parts and a 12-year limited warranty on the heat exchanger.


5. Stiebel Eltron Tempra Electric 12 Plus Tankless Water Heater

Sale
Stiebel Eltron 12 Plus Tempra, Tankless Water Heater, White
  • On-demand, continuous and unlimited supply of hot water
  • Sleek design saves space and no venting required
  • Flow Rate: 0.37 – 3.0 GPM
  • Dimensions: 19.5 x 21.5 x 8.5 inches
  • Weight: 13.5 pounds
  • Power Source: Electric-Powered
  • Warranty: 3-years parts/7-years leakage
  • Made In: Germany

It’s a known fact that installation is a lot less expensive than a comparable gas unit; however, what you may not know is that the Tempra 12 Plus is engineered to be virtually 100 percent energy efficient. This has a significant impact on your utility bill for hot water.

The Tempra 12 Plus, falls in the mid-price range, and there are no gas lines or vents to hook up and installs easy, but it does require some specific electrical connections. If you have a 240-volt service for a small condo, apartment or home with one bathroom, the Tempra 12 Plus will work just fine.

The Tempra 12 Plus, requires a minimum of 100 amp service for installation and draws 50 amps. There’s a good chance that this unit will fit into breaker spots that you have leftover and minimum modifications to the panel may not be required at all.

The GPM range in cold weather is about 1.0 to 1.5 GPM with a 90-degree rise in temperature and about 4.5 GPM with a 20-degree rise in temperature for warmer climates.


6. Stiebel Eltron Tempra Electric 20 Plus Tankless Water Heater

  • Flow Rate: 0.58 – 4.5 GPM
  • Dimensions: 19.5 x 21.5 x 8.5 inches
  • Weight: 16.1 pounds
  • Power Source: Electric-Powered
  • Warranty: 3-years parts/7-years leakage
  • Made In: Germany

The Stiebel Eltron Tempra 20 Plus is in the mid to high price range. It works great for one or two bathrooms in warm environments and condos or apartments with one bathroom in cold climates.

The Tempra 20 Plus is manufactured in Germany. All of Stiebel
Eltron’s units utilize a special feature for hectic households that require a lot of hot water usage called Advanced Flow Control. Rather than allowing a washing machine or shower to go cold, it’s technology reduces the flow of water pressure at the taps; therefore, hot water is always maintained. What this means, the regulator limits and controls the amount of cold water in the input pipe when the demands for hot water are low.

Consumers of electric whole house tankless water heaters enjoy the easy to use digital temperature controls, and this unit comes with a three-year limited warranty against defects in materials and workmanship and a seven-year limited warranty against leakage. Please read the warranty policy for more specific details.

The Tempra 20 Plus requires a minimum of electrical service of 125 amps and draws 80 amps. For structures with a 240-volt service, this unit will use about 19.2 kW while operating.


7. Bosch Tronic Electric WH27 Tankless Water Heater

Bosch WH27 Tronic Whole House Electric Tankless Water Heater, 240 Volts
  • Max 3.3 GPM at 55 degree temp rise
  • Provides endless hot water for 1 major application at a time
  • Flow Rate: 4.0 GPM
  • Dimensions: 15.25 x 4.5 x 12.5 inches
  • Weight: 22 pounds
  • Power Source: Electric-Powered
  • Warranty: 2-years parts/5-years heat exchanger
  • Made In: USA

Even though Bosch has designed this tankless water heater to be a whole-home device, it’s also engineered to heat hot water for single appliances. This device will work great for those who have light water demands or smaller homes with three or fewer occupants. It could also be used in garage apartments, guest house or a small office with a single bathroom. You will have to get used to the idea of just running one appliance at a time. For example, if you are running the washing machine and dishwasher at the same time, chances are that you will be doing the dishes in
cold water.

Due to its heat source and compact size, the Tronic WH27 is less expensive than a comparable gas model. When compared to other electric units, it falls in the mid-price range. It has a 3.3 GPM water flow with a 55-degree rise in temperature for warmer climates. Bosch engineers have achieved an Energy-Star rating of 97 percent efficiency on
this model.

The Bosch tankless water heater requires a 240-volt service, and if it’s installed with less than 240 volts, it will cause a reduction in the ability of the electric output in the heater. The Tronic WH27 also requires 120 amps of electricity and should be supplied via three 40 amp double-pole breakers in the breaker box. It’s important to make sure that your house has a 200 amp service and available space. Most older homes do not have a 200 amp service, most have a 100 amp service, so your breaker box may need an upgrade for this model.8.


8. Bosch Therm 520 HN Natural Gas Tankless Water Heater

  • Flow Rate: 3.4 to 5.3 GPM
  • Dimensions: 16.7 x 8.7 x 25.8 inches
  • Weight: 35 pounds
  • Power Source: NG-Powered
  • Warranty: 2-years parts/5-years heat exchanger
  • Made In: USA

The Bosch Therm 520 HN is truly unique, and is designed for specific customers. This is an indoor non-condensing natural gas (NG) unit with a maximum of 117, 000 BTUs. What makes this device truly unique is the ignition source, it doesn’t use any gas or electricity to start the heater. Its advanced technology uses water flow in a water-powered turbine to ignite the burner.

The electric-free ignition and battery is the ultimate solution for remote locations without electrical power and areas with frequent power outages or severe weather. If you have a remote hunting cabin, the Therm 520 HN would be a great choice for you. Natural gas will be required to run the heater; however, the ignition only needs water.

The Bosch Therm 520 HN has an Energy Factor of 0.78, and it will supply one to two hot water taps or appliances at the same time. For those in warm climates, it has a 35-degree rise in temperature and reaches water temperatures of 70 to 80 degrees with a GPM of 3.4. This innovative technology from Bosch pushes its price to the mid to high end of the spectrum, but it’s reasonably priced considering it’s one of the most advanced NG product on the market.


Summary

It’s hard to determine the best one, especially when every manufacturer has its own technology and delivers a quality product like the ones just mentioned.

One of the biggest factors for customer satisfaction starts with making sure you choose the right hot water heater that fits your home. One way to do this is with the manufacturers suggested online sizing guide or call their customer service department and get help. Since this is a significant purchase, most companies will be more than happy to assist you and answer any questions that you may have. In a lot of cases, consumers get frustrated with tankless water heaters, simply because they didn’t do the research or have the right information about their home’s hot water demands and electrical capacity.

It’s important to understand when choosing the right one to make sure you have space in your breaker box and correct electrical service. It’s unrealistic to think that the price of your new unit will include just the cost of the tankless water heater. You can’t replace an existing unit with a tankless device unless there are some modifications and electrical work done along with it.

It’s always best to consider your hot water demands before making a choice. It’s our sincere hope that you found some valuable information in our comprehensive guide because our goal is to help you find the right product that fits your home and budget.