Best Whole House Electric Tankless Water Heater Reviews

Traditional water heating in the home can be rather wasteful. We fill big tanks, some as large as 50 gallons, with water, then heat them 24/7 throughout the year, so the hot water is ready whenever we need it.

But, what about the times of day when you don’t need it? Or, what happens if the spouse opts for a tub soak, thus emptying the tub? You’d need to wait a few hours for the tank to fill back up and reheat the water to the desired temperature.

Then there are concerns about sediment in the water, which can compromise heating efficiency, and the risk of a tank leak. Too much trouble, right?

Well, there’s a solution – using the best whole house electric tankless water heater.

In this heating approach, hot water is still available when you need it, but without the troubles associated with having a tank up there. Read on to learn how these tanks work and how to acquire one.

Best Whole House Electric Tankless Water Heater Comparison Table

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

What’s a Tankless Water Heater?

 Rheem RTEX-24 24kW 240V Electric Tankless Water Heater installed in a small roomA tankless water heater is a type of water heating system that doesn’t include a tank. Instead, cold water from the home’s water supply travels via a pipe and into the heating system where it’s heated and released to the user as a constant supply of hot water. 

These water systems can provide 2-5 gallons of hot water per minute. For larger families, you can have more than one such unit to meet the increased demand. 

How a Tankless Water Heater Works

A tankless water heater works in seven precise steps from the moment you turn on the hot water tap as follows;

  1. You turn on the hot water tap.
  2. A flow sensor in the hot water system detects incoming cold water and sends a signal to the system’s control panel to initiate heating.
  3. In electric heating, the system comes on automatically. For gas-powered models, meanwhile, the control panel turns on a fan that draws air from outside. The process also opens the gate valve and lets in gas. The burner then ignites.
  4. A heat exchange, which forms part of the hot water system, draws heat from the flamers or electric heating element and transfers it to the water through special tubing. 
  5. A mixing valve within the heating system tempers the temperature of the water exiting the system. 
  6. A temperature sensor continuously monitors the temperature of the water against the selected heating setting. It adjusts the gas valve, mixing valve, and flow-regulating valve accordingly to deliver water at the desired temperature. 
  7. A sealed vent (sometimes there are two such vents) exiting the home through the wall or roof carry any exhaust gases outside the house. 

What Size Tankless Water Heater Do I Need for my Home?

Sizing tankless water heaters is one of the most important steps in the shopping process. You need just enough water to suffice your family’s needs. To determine a BTU level that would be strong enough but not too much (wasteful and unnecessarily expensive) for you needs, the HVAC expert will consider three key factors;

  • The water temperature as it enters the heater: This helps the installation expert determine the amount of heat (in BTU) required to raise the incoming water to the desired temperature level (usually 120 degrees). The increase is known as temperature rise
  • The peak demand for hot water in the house: Peak demand is the sum of flow rates for every appliance and fixture that would use the hot water system at any given time. The total is usually slashed by 20% (for technical reasons).
  • The heater (determined by the Uniform Energy Factor): This is usually indicated on the product label and is typically around 95% for standard tankless heaters. 

The final heating need in BTU is calculated by plugging the BTU-per-gallon and peak-demand figures into a sizing calculator. Suppose the value lies between two heater models. In that case, you will pick the higher one and where it exceeds 198,000 BTUs (or 36,000 watts/123,000 BTU for electric models) which is the maximum BTU rating available for residential tankless heaters, you’d need two smaller units.  

In general, however, you need about 140,000 BTU for a single-bath home with 1-2 users, a 190,000 BTU unit for a two-bath home with 2-3 users, and 380,000 BTUs 3-bath Home with 3-5 users. 

Calculating Temperature Rise and Water Flow Rate

The two terms, temperature rise, and flow rate are widely debated topics. Temperature rise is simply the difference between the incoming water temperature and the desired output temperature. 

If the incoming water is at 50°F(10°C) and you desire a hot shower at a temperature of say 120°F(49°C), then the required temperature rise is 120-50/49-10 = 70°F/39°C. 

The water flow rate is a little more demanding to calculate. You’ll need a flow rate chart for your location for accurate calculations. However, the standard rates, in gallons-per-minute (GPM), are as follows;

  • Tub = 4.0 GPM
  • Shower = 2.5-3.0 GPM
  • Washing machine = 2.0 GPM
  • Dishwasher = 1.5 GPM
  • Kitchen sink = 1.5 GPM

So, if you expect to run two showers at the same time, even if occasionally, your flow rate is 2 x 2.5/3.0 = 5.0/6.0 GPM. If you also intend to use the warm water for the washing machine (one), you need to add 2.0 GPM to bring your total to a maximum 8.0 GPM requirement. 

Pros and Cons of Tankless Water Heaters

how the best whole house electric tankless water heater worksAlso known as on-demand heating systems, tankless water heaters come with several advantages as well as a few downsides as follows;


The tankless design is perhaps the tankless water heater’s biggest advantage. You don’t need to worry about buying a hot water tank or replacing one.

Maintenance of hot water tanks is also often a challenge. When you invest in a tankless water heating system, you forget about that too. Additionally;

  • Significant cost savings: Not only do you save on the cost of buying and maintaining a water heating tank, but the energy savings are also substantial. According to, you stand to save 27-50% on fuel, saving the average family $100 per year. 
  • Continuous water supply: Water heating systems that depend on a tank are only useful when they are full of hot water. As soon as the tank runs dry, the convenience is lost. Tankless water heaters guarantee a consistent supply of hot water.
  • They are more compact: A typical water heating system with a tank takes up a lot of space. Considering that federal regulations now demand even thicker insulation for these tank-type systems, they can take up considerable space. Tankless water heaters, by comparison, are about the size of a suitcase and easily hand on the wall. 
  • They are safer: A tank-type water heater creates an ever-present water damage risk. If the tank leaks, water damage is inevitable. Tip-over and legionella bacteria are other inherent risks. Tankless heaters are free of these risks. 
  • Longer life: Finally, a tankless water heater is guaranteed to last many years longer than the standard tank-type heater. In particular, gas-powered tankless heaters last up to 20 years, which is 2-3x longer than the average tank0style water heater. 


Despite the many advantages, though, tankless water heaters come with a few challenges. Common downsides include;

  • Higher upfront costs: This is the biggest challenge with tankless water heaters. Whereas a standard tank-type heater costs about $400, a basic tankless model costs at least 2.5x (i.e., $1000). Recouping the extra investment may take a while. 
  • Sensitive to slow flow: Unlike the tank-type heating system that usually works as long as the tank is full, tankless models become problematic if water flow isn’t normal. Too much scale buildup in the pipes and clogging in the faucets and shower heads may cause the system to shut off. 
  • Consume a lot of electricity: A standard electric tankless water heater draws up to 25,000 watts than about 5,000 watts for a tank-type model. So, prepare for a sizeable jump in your annual power bill. 

Best Whole House Electric Tankless Water Heater Reviews

1. Ecosmart ECO 36 36KW 240V Electric Tankless Water Heater

Ecosmart ECO 36 36kw 240V Electric Tankless Water...
  • Sleek and compact design with digital output temperature display
  • ECOSMART tankless water heaters are 99.8-percent energy efficient
  • Manufactured in United States
  • Pipe Fittings:3/4 inch NPT
  • Required Breaker:4 x 40 A

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

 The ECO 36 is Eco Smart’s largest electric tankless heater using the patented self-regulating technology. The smart technology is ideal for areas where incoming water can reach temperatures as low as 37°F (the average water temperature is about 50°F).

The ECO 36 is better still capable of heating up to 3.5 gallons per minute, equivalent to using the shower, kitchen sink, and dishwasher simultaneously.

For homes in areas with standard water temperatures, such as the southern parts of the USA, it can handle up to 6 gallons per minute, equivalent to running two showers at ago (though the manufacturer says it can handle as many as four showers simultaneously). 

Other ECO 36 includes a digital temperature controller that allows you to increase temperatures in 1°F increments and the compact 17 x 19 x 3.8-inch design. It weighs a paltry 18 pounds and comes with a limited lifetime warranty. 


  • Stylish, advanced design
  • Control temperature in 1°F increments
  • Copper and stainless steel components
  • Limited lifetime warranty


  • No remote control
  • Requires 240V wiring

2. Stiebel Eltron Tankless Heater – Tempra 36 Plus – Electric Water Heater

Stiebel Eltron Tankless Heater – Tempra 36 Plus...
  • On-demand, continuous and unlimited supply of hot water
  • Sleek design saves space and no venting required
  • Electronic switch activated for virtually silent operation. Phase- single 60 Hz. Voltage- 208 V. Wattage- 27 kW
  • Copper sheathed heating element housed in copper cylinder
  • 7 Years leakage and 3 years parts complete warranty

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

The Tempra 36 Plus from Stiebel Eltron is a made-in-Germany tankless water heater featuring an advanced Flow Control patented technology. The technology automatically maintains water temperature constant for complete comfort.

It does this by slightly reducing water flow if the demand for hot water exceeds capacity. The result is 15-20% greater energy savings compared to traditional heaters.

Another standout feature of the Tempra 36 Plus is that the system doesn’t need venting. Additionally, the unit has a digital display for accurate temperature delivery and maximum energy efficiency.

Pre-set temperature buttons, water control monitors, and intelligent self-modulating technology are the other important features.

The Tempra 36 delivers up to 7.5 GPM and outputs water at temperatures between 86°F and 140°F. It’s very light and is ANSI, CSA, and NSF certified. It’s also UL Listed. 


  • Reaches up to 36,000 Watts (36KW)
  • Durable copper sheath and cylinder
  • CSA, ANSI Certified, UL Listed
  • 3-year parts warranty
  • 7-year leak warranty


  • One of the more pricey options
  • Requires professional installation 

3. Bosch Thermo Technology WH27 Tronic 6000 C Electric Tankless Heater

Bosch Thermotechnology - WH27 Tronic 6000 C...
  • CONVENIENT TANKLESS HOT WATER HEATER: 26.9 kW tankless whole house electric water heater provides hot water when needed, for as long as needed
  • EASY INSTALLATION: Can be installed virtually anywhere for commercial or residential applications
  • CONSISTENT TEMPERATURE: Polymer encased elements & built-in flow sensor ensures constant output temperature
  • STABILITY & CONTROL: External temperature control knob & superior temperature stability and control
  • GREAT EFFICIENCY: 97% thermal efficiency with minimal stand-by loss

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

The Model WH27 from Bosch Tronic is a 6000 C Series tankless heater can be installed virtually anywhere in the house. It packs 27,000 watts and is designed to last up to 20 years (standard tankless heaters only last 6-12 years). 

Other features that set the WH27 apart are the electronic flow sensor and element modulation technologies that combine to ensure a consistent and reliable output temperature. An innovative scale prevention technology allows you to monitor temperature control and stability. 

This unit is hard-wired (professional installation recommended) and supports flow rates of up to 3.5 GPM (at 45°F). It’s backed by a 5-year heating module warranty and a 2-year parts warranty. 


  • Long life (up to 20 years)
  • 97% thermal capacity 
  • Scale-prevention technology
  • 2-year parts warranty 


  • It’s very sensitive to pressure
  • Requires professional installation 

4. Camplux Electric Tankless TE27 Whole House Instant Water Heater

Camplux Tankless Water Heater Electric 27kW 240V,...
  • Three Savings: With an efficiency of 99.8%, this tankless electric water heater can save up to 60% on water heating costs. Hot water in three seconds after switching on saves time, easy to get water between 86°F - 125°F; Small size 15.15 x 10.23 x 3.66" saves space
  • Safety Protection: The instant water heater comes with NFS and ETL certification and overheating protection. When the temperature is too high, the water heater will automatically trip to ensure the safety of you and your family
  • Smart Design - The tankless hot water heater design with touch control & digital display, smart and easy to set temperature. Comes with a remote smart controller, you can set the desired temperature even if you are not in front of the instant water heater
  • Durable: The on-demand hot water heater is equipped with a pressure relief valve, which can drain the water after use in winter, which can effectively prevent the freezing and cracking of the water pipe in the water heater so that the water heater can be used for a longer time
  • Tips: The 27kW 240V tankless water heater requires 3 x 50 AMP double pole breakers, 8 AWG wire, and water connection 3/4” NPT. The min. Water Flow is 0.85GPM. 2-year limited warranty and 24/7 customer support services

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

If you’re looking for a stylish, digitally-controlled point-of-use water heater, then the Camplux TE27 takes the cake.

This unit is outstandingly beautiful. Better still, it comes with touch/smart/remote controls and a digital display. It’s also leak-proof and implements overheating protection, so you don’t have to worry about burn risk.

The heater is rated at 87,000 BTU and delivers hot water between 86°F and 125°F. It needs a flow of just 0.85 GPM to be activated. It mounts easily (on the wall) and can be mounted at any angle (180 degrees). 

The TE27 is compact at 18.9 x 14.5 x 5.7 inches, weighs 17.76 pounds, and is built from durable stainless steel. It’s also waterproof and ETL Certified. 


  • Styling, modern look
  • Digital and smart controls
  • Inexpensive (compared to the rest)
  • Durable stainless steel build
  • Overheating protection for safety


  • Best for smaller families 
  • Requires circuit breaker wiring

5. Rheem 240V 3 Heating Chambers RTEX-24 Residential Tankless Heater

Rheem RTEX-24 24kW 240V Electric Tankless Water...
  • ON/OFF Dial Control with adjustable digital temperature display
  • Self-modulating power control
  • 24kW Model Flow Rate: up to 5.9 GPM for RTEX-24
  • Bottom 3/4" NPT water connections
  • On demand, consistent and continuous hot water

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

The RTEX-24 from Rheem is a professional, classic tankless water heater that offers a continuous flow of hot water on-demand.

It features a compact design with a control knob at the front, allowing you to adjust temperatures in 1°F increments. It heats to between 80°F and 140°F at 99.8% energy efficiency.

The heating elements are made from a robust copper I’mmersion for durability and threaded for easy replacement. An external digital thermostatic LED display lets you monitor temperatures as you make the adjustments. 

This water heater supports flow rates up to 7 GPM, but it depends on the required temperature rise. Where a rise less than 35F is required, you can get up to 7 GPM, for a 35F to 45F rise; you get 4.68 GPM to 3.64 GPM. Rises greater than 65F, however, are only supported at 2.5 or lower GPM flow rates.


  • 24,000 watts (24KW)
  • 1°F temperature increments 
  • Durable copper heating elements
  • LED display for temperature monitoring
  • 99.8% energy efficiency 


  • No remote control

6. Eemax EEM24027 27,000 –Watt Electric Tankless Water Heater

Eemax EEM24027 Electric Tankless Water Heater,...
  • Tankless water heater provides a continuous supply of hot water and only heats the water you need, when you need it
  • Breaker: 3 x 40 AMP double pole breakers
  • Wire Gauge Required: 3 X 8 AWG
  • Compact size saves valuable storage space

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

Finally, the EEMAX EEM24027 is a compact and stylish tankless water heater that uses three heating elements for consistent and high-capacity hot water delivery. You get to choose between a copper-clad or zinc-plated copper-clad sheath (this particular model uses a copper sheath).

The heater is can comfortably support the simultaneous use of one shower and two sinks in the cold climates and up to four showers in warmer weather. The even better part is that you need just 0.25 GPM flow to turn it on. It heats water to between 80 and 140°F.

The appliance is made from stainless steel for durability and finished in a striking blue color. It’s also comparably lightweight at 13.7 pounds and takes up just 17 x 17 x 3.7 inches on the wall. You get a five-year leaks warranty and one-year parts warranty upon purchase.  


  • Commendable 5.3 GPM flow rate
  • Self-modulating technology 
  • Durable stainless steel build
  • 1-year parts warranty 
  • 5-year leak warranty


  • You need 3 x 220V circuit breakers

Whole House Electrical Water Heater Energy Saving Tips 

As already mentioned, tankless water heaters are incredibly efficient and convenient. At the same time, though, they consume a lot of electricity. 

The following tips should help you get the most from the heating system while saving on energy;

Turn Down the Thermostat

This often results in the biggest energy savings. When you buy the heater, you’ll notice that the temperature is set at 140°F. That’s the standard. Most homes don’t need 140°F water heating – about 120°F should be sufficient. Since every 10°F temperature reduction results in a 5% saving, the 20°F reduction should cut your power bill by about 10%. You can also opt to buy Google Nest Learning Thermostat which is a smart steam heat thermostat that helps you save energy.

Reduce your Consumption

The maximum flow rate we discussed above has a massive impact on your energy bill. If you want to significantly cut the bill, reducing that flow rate can be instrumental. So, how do you cut the flow rate? By lowering your hot water usage. Don’t leave the water running while you brush your teeth or doing the dishes. Also, consider investing in aerators in all your faucets to cut the flow. 

Insulate All Exposed Piping

This might not cut your bill by much given that tankless water heaters don’t require much piping anyway, but you’re still guaranteed some savings. It’s been shown that when you insulate piping in the bathroom, for instance, water comes out of the faucets/shower 2-4 degrees warmer. This may allow you to lower the thermostat setting further.

Ensure Regular Maintenance

Down the road, lack of maintenance is the leading cause of even greater energy consumption. Consider a situation where there’s a sizeable buildup in the pipes, for instance. The water minerals tend to increase the amount of heat needed to raise the temperatures to the desired level. Even worse, the partial blockage in the pipes means you’ll need to spend more time in the bathroom (thanks to reduced flow), thus more energy consumption. 

Electric Tankless Heater Maintenance 

Electric tankless water heaters are low-maintenance appliances. However, that doesn’t mean that maintenance isn’t required. 

Hard water, for instance, is an ever-present risk in both tank-type and tankless water heating systems unless you have a water heater for hard water.

Another name for mineral-laden water, hard water contains significant amounts of magnesium and calcium. Hard water requires more energy to achieve the desired temperature rise. 

Additionally, mineral buildup on the heat exchanger can cause irreversible damage. In extreme cases, it results in malfunction, necessitating the exchanger’s replacement, or the entire heating system. The worst part – most manufacturer warranties don’t cover mineral buildup or related damages.

So, what type of maintenance is needed?

  • Routine descaling: At least once a year, your system should be descaled by a professional to remove any buildup around the heating elements. Depending on your location, such descaling may even be necessary twice a year. The professional will also help fine-tune the system for optimal performance.
  • Filter cleaning: All hot heating systems comprise filters that block out debris and other dirt particles. These filtration systems must be cleaned regularly to ensure that only clean water comes out of your faucets. Also, the filters need replacement when they outlive their useful lives. 


Tankless water heaters can be an invaluable investment, especially in smaller families where most of the hot water in tank-type water heating systems go to waste. With tankless systems, the heating is on-demand, guaranteeing significant energy and cost savings. 

Electric tankless heating systems are incredibly valuable as they are very quiet and only about one-third the size of gas-powered models (which are also very compact). If you’re looking to replacing your heating system, you should seriously consider one of the electric tankless models. 

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Ronald Watford, the owner of Quality Home Air Care, is a qualified HVACR technician and manages the team of expert writers on this site. He believes that educating homeowners about HVAC systems is one of the most impactful aspects of his job.