6 Best Electric Tankless Water Heaters (Powered By 240V, 50-150 A)

On-demand hot water is quickly becoming the new modern standard.

The easiest way to get on-demand hot water is by installing an electric tankless water heater.

Every household has access to an electric grid; installing an electric tankless heater is much more convenient.

The best electric water heaters have several advantages over traditional storage heaters with tanks. These are:

  • High energy efficiency. Electric tankless heaters have an energy factor rating (EF rating) of above 0.9. That means that more than 90% of electricity is used to heat water. Less than 10% of energy is lost; storage heaters have 30-50% energy losses.
  • Easy to install and maintain. With gas heaters, you need access to natural gas or propane, and you have to inspect the installation every year. With electric tankless heaters, however, you have a quick and affordable installation process and little to no maintenance.
  • Durability. The best electric tankless heaters will last about 20 years. Storage ones have a lifespan of about 13 years. Additionally, most electric tankless water heater offers superb warranties, with up to a 10-year warranty on the heat exchanger.
  • Come in various sizes (measured in kW). Sizes of electric tankless heaters range from 10 kW up to 40 kW. If you have a small household, you can choose the ones closer to 10 kW. For a big household and increased hot water needs, you can choose the powerful 36 kW electric tankless heaters. Low amp tankless water heaters like Stiebel Eltron 230628 are very sought after.
  • Cheaper than gas alternatives. Gas tankless water heaters can easily cost more than $1,000. Tankless water heaters that are powered by electricity, however, cost less than $1,000. You can get the best ones for half the cost of the gas heaters.

Once you have it, you get all the convenience that goes with a durable, low maintenance electric tankless heater. You can have peace of mind – the on-demand hot water supply is taken care of.

Below you will find a list of the best electric tankless heaters. These choices are made based on recommendations, specifications, and price-performance:

List Of The Best Electric Tankless Water Heaters (With Specs And Reviews)

Electric Tankless
Water Heater:
Important Specs:
#1 Stiebel Eltron – Tempra 24 Plus

4.8 out of 5 stars
Check on Amazon
Max. Water Flow: 5 GPM
Energy Factor: 0.99 EF
Water Temp: 86˚ to 140˚F
Noise: 56 dBa
Power: 24 kW (100 A, 240 V)
Weight: 16.1 lb
Warranty: Leakage (7 years),
Parts (3 years)
Country: Germany
Reviewed size: 24 kW.
Available sizes: 12 kW, 15 kW,
20 kW, 24 kW, 29 kW, 36 kW.
#1 Stiebel Eltron – Tempra 24 Plus

4.5 out of 5 stars
Check on Amazon
Max. Water Flow: (Estimated) 5.5 GPM
Energy Factor: NaN
Water Temp: 80°F - 140°F
Power: 27 kW (112.5 A, 240 V)
Weight: 10.98 lb
Warranty: Limited Lifetime Warranty
Country: USA
#3 Rheem 240V 2 Heating Chambers RTEX-18

4.1 out of 5 stars
Check on Amazon
Max. Water Flow: 4.4 GPM
Energy Factor: NaN
Water Temp: Up to 140˚F
Noise: NaN
Power: 18 kW (75 A, 240 V)
Weight: 8.5 lb
Warranty: Heating Chamber (5 years),
Parts (1 year)
Country: USA
#4 Stiebel Eltron 230628

4.2 out of 5 stars
Check on Amazon
Max. Water Flow: (Estimated) 3.5 GPM
Energy Factor: NaN
Water Temp: 86˚ to 140˚F
Power: 12 kW (50 A, 240 V)
Weight: 5.95 lb
Warranty: Leakage (7 years), Parts (3 years)
Country: Germany
#5 Sio Green SIO18 v2 Infrared

4.4 out of 5 stars
Check on Amazon
Max. Water Flow: 6.6 GPM
Energy Factor: NaN
Water Temp: NaN
Power: 18 kW (80 A, 240 V)
Weight: 28.3 lb
Warranty: NaN
Country: USA
#6 Eemax EEM24027

3.8 out of 5 stars
Check on Amazon
Max. Water Flow: (Estimated) 5.5 GPM
Energy Factor: NaN
Water Temp: NaN
Power: 27 kW (112.5 A, 240 V)
Weight: 13.75 lb
Warranty: NaN
Country: USA

#1 Stiebel Eltron Tempra Plus (Best Electric Water Heater)

German company Stiebel Eltron is widely renowned as the best electric water heater producer. The best heater the German engineers have come up with is the Tempra Plus, which comes in 6 different sizes.

The Stiebel Eltron Tempra Plus’s main advantage – the reason it’s the best electric tankless heater – is the patented Advanced Flow Control. This tech goes the extra mile to maintain powerful hot water flow automatically. If the capacity is overreached, the AFC will reduce the hot water flow and make the necessary adjustments to increase the energy-efficiency of the heat exchanger.

That, coupled with a condenser, brings the Stiebel Eltron Tempra Plus’s energy-efficiency up to 0.99 EF. That means for every 1 dollar of electricity spend, $0.99 will go directly into heating water. Only 1% will be lost. For comparison, other above-average energy-efficient electric heaters have an EF rating of 0.95.

The device itself is very compact; the best selling 24 kW Tempra Plus weighs only 16.1 lbs.

stiebel eltron best tankless water heater
Stiebel Eltron Tempra Plus is the best tankless water heater. It’s electric, extremely energy-efficient, and has some German engineering class of reliability.

It’s powerful enough to handle the hot water needs of the whole household easily. It can raise water temperature from 86˚F to a maximum of 140˚F. To achieve such flow, it will require a 150 A electric grid. Modern households already have that; the older ones will need an electricity grid upgrade.

You can choose between 12 kW, 15 kW, 20 kW, 24 kW, 29 kW, and 36 kW sizes. The most popular model that fits most households is the Stiegel Eltron Tempra 24 kW Plus. However, if you have a large household, you should invest in the most powerful 36 kW model. You won’t have any worries about not having enough on-demand hot water anytime soon (for 20 years or so).

Stiebel Eltron 239222 Tempra Plus

  • Most energy-efficient tankless heater with 0.99 EF
  • Uses patented Advanced Flow Control to control the hot water flow better than any other heater
  • Wide range of water temperature (86˚F to 140˚F)
  • Small (16.1 lbs) but very powerful
  • Wide range of available models (from 12 kW to the strongest 36 kW)
  • Reliable: German engineering is always a plus
  • Given the advanced tech, it is on the expensive side
  • Minimal recommended electric service of 150 A; may need an upgraded electric grid

#2 EcoSmart ECO 27 (Most Popular Electric Tankless Heater)

It’s not difficult to see why EcoSmart ECO 27 is such a hit with consumers. It’s small (less than 4 inches wide), highly energy-efficient (can save up to 50% on hot water costs), and affordable. The fact that you can get an eco-friendly 27 kW electric tankless heater for less than $500 is its strong selling point.

In fact, if you check it out on Amazon, it has more than 2000 existing ratings with an aggregate average rating of more than 4 stars. When it comes to electric hot water heaters, that’s a superb rating.

It has a low 0.3 GPM activation flow; that means you will have an immediate hot water flow even at very low water flow. Other comparable devices have an activation flow of 0.5 GPM. This makes the EcoSmart ECO 27 that much more convenient and energy-efficient.

To achieve the 27 kW of electric power, you will need a voltage of 240 V and a maximum amperage of 112.5 A. To get that grid, you usually have to have 3 40 A breakers. Combined, they can deliver 120 A electricity, which is more than enough to power the EcoSmart ECO 27.

eco friendly tankless water heater that can save more than 50 percent of water costs
EcoSmart ECO 27 kW was designed as the most eco-friendly tankless water heater.

EcoSmart ECO is made to be both environmentally-friendly and compact. In fact, it’s the smallest electric tankless water heater if you check just the dimensions (Height x Width x Depth = 17 x 17 x 3.625 inches).

For an indoor electric heater, it’s important to be small and visually appealing. EcoSmart ECO 27 is both. If you have a smaller household, you can also opt for it’s smaller 18 kW cousin.

EcoSmart ECO 27 kW

  • Best selling electric tankless water heater on Amazon
  • Eco-friendly features include 0.3 GPM minimal flow and self-modulating tech
  • Can save up to 50% on water heating costs
  • The smallest and lightest device on the list
  • Lower price than premium heavy-hitting tankless heaters
  • Needs three 40 A breakers to achieve 27 kW power
  • Might not be strong enough for big houses

#3 Rheem 240V 2 Heating Chambers RTEX-18 (Best Small Electric Tankless Heater)

Most people buying electric tankless heaters don’t know the available brands. However, if they know one, it’s Rheem. This is an American company that has been making heaters for decades now.

Their most popular electric tankless heater is the Rheem RTEX-18. It has 2 heating chambers and can achieve the full power of 18 kW. The maximum hot water flow in ideal conditions is 4.4 GPM. That is usually enough for small and middle-sized households. However, big households with 5 or more people will require a more powerful tankless heater that runs on electricity.

The one convenient thing every electrician installing the Rheem RTEX-18 will value is the standard voltage (240 V) and low amperage for an electric tankless heater (75 A). Usually, the powerful heaters need a 100 A or even 200 A grid. The 75 A captures that ideal balance between a powerful-enough electric heater without the difficult electric grid update.

rheem 18 kw is the smallest and most affordable electric tankless heater
Rheem 18 kW Classic Series is a small but powerful electric tankless water heater that weighs less than 10 lbs.

The appealing part of the RTEX-18 is also the price. Because it’s not that powerful and doesn’t include the expensive new-age technology, it is priced below $500.

For a solid, durable, and reliable electric tankless heater powered by 75 A, that is as fair a price as any.

Rheem 18kW Classic Series

  • Best small electric tankless heater for small households
  • Easy to use and easy to install (user-friendly)
  • In most cases, you won’t need to upgrade your electricity grid (runs on max. 75 A)
  • Costs less than $500 (very affordable price for a reliable heater)
  • Not appropriate if you have big simultaneous hot water needs (big household of 5 or more people)
  • Warranty is not exactly the top of the line

#4 Stiebel Eltron DHC-E 12 (Smallest Electric Low Amp Water Heater)

As stated before, the German company Stiebel Eltron produces the top of line electric tankless water heaters. They have developed a small version device for small households or medium-sized households in the USA’s southern part (where the intake water temperature is most optimal). This is the Stiebel Eltron DHC-E 12 (Model: 230628):

 Stiebel Eltron 074424 dhc-e 12
Stiebel Eltron DHC-E 12 is the best small and affordable electric water heater.

The beauty of the smallest 12 kW electric tankless water heater is that you don’t have to upgrade your electricity grid and still get on-demand hot water for simultaneously running 1 shower and 1 water faucet.

The Stiebel Eltron DHC-E 12 is powered by a 240 V (standard) voltage and 50 A. 50 A grid is what most household electricity grid can already handle; there is no need for expensive electricity grid upgrades. Basically, you almost plug the electric tankless water heater in and have a hot shower.

It also has a 0.3 GPM minimum activation flow. That means that even if you use the low-GPA faucets, you will immediately get hot water. It’s has a wide range of available hot water temperatures, anywhere from 86°F to 140°F.

This device is designed as a single sink point-of-use while also capable of a multi point-of-use electric tankless heater. Like all newer Stiebel Eltron heaters, it comes with self-modulating water flow technology, which further increases energy efficiency. It is available for less than $300.

Stiebel Eltron DHC-E 12

  • Smallest tankless water heater, primarily for single point-of-use (shower, for example)
  • No need to upgrade electricity grid (runs on 50 A with a power of 12 kW)
  • Some even smaller models are available
  • In total, it costs less than $300
  • Not appropriate if you have big simultaneous hot water needs
  • Multi point-of-use is limited

#5 Sio Green SIO18 v2 (Best Infrared Electric Tankless Water Heater)

Talk about NASA technology being incorporated to deliver you on-demand hot water. Sio Green SIO18 v2 is a special tankless water heater that uses electricity to fire up far infrared lights. In turn, the infrared light heats water in Quartz tubes located inside the Sio Green heater.

This technology was usually reserved for the commercial tankless water heater. Sio Green is the first company to make infrared electric tankless heaters for residential use.

Everything else is pretty much the same as with all-electric tankless water heaters. You have the 3/4 inch NPT water connections, 240 V, and 80 A electric power grid. Most electric grid can handle the Sio Green SIO18 v2’s electric power needs (without the need to upgrade the grid).

The best thing about using the Quartz tubes is that you don’t have to worry about metal corrosion or calcium deposits. The electrically-heated up water is not touching metallic parts; it’s only touching Quartz tubes. No metal, no metal corrosion, simple enough.

infrared tankless water heater with quartz tubes to heat water quickly
Sio Green V2 uses far-infrared light to heat the water in Quartz tubes. That prevents both corrosion and calcium deposits.

This, in turn, reduced maintenance costs. The infrared technology doesn’t only get you the bragging right of ‘Hey, I have NASA tech infrared tankless water heater powered by electricity’ and makes the Sio Green V2 highly energy-efficient.

Quartz absorbs the far-infrared light at a high rate and heats water molecules in no time. Because of the high level of sophistication that goes into designing these devices, the Sio Green v2 is more expensive than comparable standard electrical tankless water heaters.

Sio Green V2 18kW Model

  • Uses NASA-developed tech of infrared light coupled with Quartz tubes
  • No corrosion or calcium deposits
  • Lower-than-average maintenance costs
  • Very energy-efficient
  • Two models available: 9 kW and 18 kW
  • For essential an electric heater, it’s quite heavy (28.3 lbs)
  • Higher price because of the next-gen technology

#6 Eemax EEM24027 (Blue Tankless Hot Water Heater)

Heaters vary in specifications quite a lot. However, if you install an electric tankless water heater indoors, the color should also play a role. Sadly, most of the heaters are either white, grey, or silver. The Eemax had this simple idea: ‘Just make a blue one’. And the Eemax EEM24027 was born.

Regarding the specifications, the Eemax EEM24027 comes with self-modulating technology for optimum hot water use. It can achieve the maximum power output of 27 kW; 240 V and 112.5 A electric grid is required.

But most importantly, it blue and beautiful. In fact, it can enrich your interior design:

blue electric tankless water heater
Eemax EEM24027 comes in a blue color that may be visually appealing to many households.

It has a slim and compact design. This makes it a perfect addition to homes that are in need of a less neutral and visually appealing electric tankless water heater.

Eemax EEM24027

  • Blue colored tankless water heater
  • Decent HVAC specs
  • Very energy-efficient
  • Good power/weight ratio
  • Only 27 kW model available
  • Doesn’t have top specs compared to the best electric tankless water heaters

2 thoughts on “6 Best Electric Tankless Water Heaters (Powered By 240V, 50-150 A)”

  1. Heaters vary in specifications quite a lot. However, if you install an electric tankless water heater indoors, the color should also play a role. Sadly, most of the heaters are either white, grey, or silver.

  2. No.2 works great. I installed this water heater a few months ago and with the AC running more often (we live in Florida) the electric bill is lower than it was at the same time last year. The setup was easy and very quick there was hot water.


Leave a Comment