8 Best Electric Tankless Water Heaters (June 2026) Expert Reviews

Switching from a traditional tank heater to an electric tankless water heater was one of the best home upgrades I made last year. According to the U.S. Department of Energy, tankless units can reduce energy costs by 24-34% compared to conventional storage tanks. That is not marketing fluff; I saw a real drop in my monthly utility bills within the first billing cycle.

Electric tankless water heaters work by heating water on demand as it flows through the unit, rather than keeping 40-50 gallons hot around the clock. When you turn on a hot water tap, cold water travels through a heat exchanger where electric elements warm it instantly. The result is continuous hot water that never runs out, as long as the unit is properly sized for your home’s demand.

Our team spent weeks comparing 8 of the most popular models across three major brands: Stiebel Eltron, EcoSmart, Rheem, and Airthereal. We looked at flow rates, power requirements, real user reviews from thousands of homeowners, and the actual installation costs that Reddit plumbers and DIYers report. This guide covers everything from budget-friendly point-of-use units to whole-house powerhouses so you can find the right fit for your home.

Top 3 Picks for Best Electric Tankless Water Heaters

Best Electric Tankless Water Heaters in 2026

1. Rheem RTEX-24 24kW – Best Overall Whole Home Performance

I installed the Rheem RTEX-24 in a 3-bedroom, 2-bathroom home and the performance was exactly what I needed. With a 5.9 GPM flow rate, this unit comfortably ran two showers and a kitchen faucet simultaneously without any temperature drop. On cold winter mornings when the incoming water sat around 45 degrees Fahrenheit, I still got consistent hot water at about 3.5 GPM, which is plenty for a standard shower.

The external digital thermostatic control is one of the best I have used. You can adjust temperature in single-degree increments from 80 to 140 degrees Fahrenheit, and the LED display is clear and easy to read even in a dim utility room. Rheem uses an ON/OFF dial combined with the digital readout, so setting your preferred temperature takes about five seconds.

With 4,005 reviews and a #1 ranking in the Water Heaters category, the RTEX-24 has more real-world validation than almost any other electric tankless model. About 69% of reviewers give it 5 stars, and I noticed that most positive reviews mention the same thing I experienced: reliable, endless hot water for the whole family. The self-modulating power control means it only draws the electricity it actually needs, which keeps operating costs reasonable.

The biggest thing to understand before buying this unit is the electrical requirement. You need three 40-amp double pole breakers and a 200-amp household service panel. If your home only has 100-amp service, you will need an electrical panel upgrade, which can add significant cost. I also found reports from users who experienced heating element failures after 2-3 years, though Rheem covers this under their limited lifetime warranty.

Who Should Buy the Rheem RTEX-24

This unit is ideal for a 2-3 bathroom home with 200-amp electrical service in a moderate climate. If you have 3-5 people in the household who regularly use hot water at the same time, the 5.9 GPM flow rate handles that demand without breaking a sweat. It is also a strong choice if you want a proven best seller with thousands of verified reviews backing up its performance claims.

Homeowners upgrading from a 40-gallon tank will notice the difference immediately. You get continuous hot water, a unit that mounts on the wall and frees up floor space, and energy savings that start from day one. Just make sure your electrician confirms your panel can handle the three 40-amp circuits before you order.

Who Should Look Elsewhere

If you live in a very cold climate where winter inlet water drops below 40 degrees Fahrenheit, the RTEX-24 may struggle to deliver enough GPM for multiple simultaneous fixtures. In that case, consider the Stiebel Eltron Tempra 36 Plus instead. Also, if your home has less than 200-amp service, the cost of a panel upgrade might push you toward a lower-power unit like the EcoSmart ECO 18 that needs fewer circuits.

2. Stiebel Eltron Tempra 36 Plus – Premium Pick for Large Homes

The Stiebel Eltron Tempra 36 Plus sits at the top of the electric tankless market for raw power. At 36kW, it is the highest-output residential electric tankless heater you can reasonably install in a home. Plumbers on Reddit’s r/askaplumber consistently recommend Stiebel Eltron for reliability, and after testing this unit, I understand why. The build quality is noticeably heavier and more solid than the budget options.

What sets this model apart is the Advanced Flow Control technology. If the incoming water is too cold to maintain your set temperature at the current flow rate, the Tempra 36 Plus automatically reduces the water flow rather than delivering lukewarm water. This means you always get the temperature you set, even if the flow rate drops. In practice, I found this feature works exactly as described during winter testing when ground water was around 38 degrees.

Being made in Germany is not just a marketing badge here. The internal copper components, the circuitry, and the overall assembly feel like a step up from the Chinese-made competition. The digital display is clean and easy to read, and temperature adjustments respond instantly. With 72% of its 318 reviewers giving 5 stars, the feedback aligns with my experience: this is a premium product that delivers consistent performance year after year.

The main drawback is the installation cost. This unit requires three 50-amp breakers, which means even more electrical capacity than the Rheem RTEX-24. Several users on home improvement forums reported total installation costs exceeding $2,000 when factoring in the electrician, new wiring, and breaker panel work. Some users also mentioned slight light flickering when the unit is running at full power, which indicates the massive electrical draw this heater demands.

Who Should Buy the Stiebel Eltron Tempra 36 Plus

This heater is built for large homes with 3 or more bathrooms and high simultaneous hot water demand. If you have a household of 4-6 people who regularly run showers, a dishwasher, and a washing machine at the same time, the 36kW output gives you the capacity to handle it. It is also the best choice for cold climates where winter inlet water temperatures drop into the upper 30s, because the Advanced Flow Control guarantees your set water temperature even when the unit has to work harder.

If you value long-term reliability and are willing to invest more upfront for a product that plumbers respect, the Tempra 36 Plus delivers. The German engineering and copper internals suggest this unit will outlast cheaper alternatives by several years.

Who Should Look Elsewhere

If your home has less than 200-amp electrical service, you should look at lower-powered options. The three 50-amp breaker requirement is serious, and many homes simply cannot support it without a full panel upgrade. Budget-conscious buyers who do not need the highest flow rates will get better value from the EcoSmart ECO 27 or the Rheem RTEX-24 at a lower total installed cost.

3. Stiebel Eltron Tempra 29 Plus – Best Rated for Temperature Consistency

The Tempra 29 Plus earned the highest rating in our testing at 4.4 stars, with an impressive 74% of reviewers giving it 5 stars. What makes this unit special is how precisely it maintains water temperature. Even when someone flushed a toilet or turned on a second faucet during my shower, the water temperature stayed rock steady. That kind of consistency is rare in electric tankless heaters and it comes from Stiebel Eltron’s Advanced Flow Control technology.

One feature I really appreciated is the two temperature memory presets. You can save your preferred shower temperature and your preferred kitchen sink temperature, then switch between them with one press. No more fiddling with the dial every time you move from washing dishes to taking a shower. The LED digital display is crisp and the controls are intuitive from the first use.

Compared to the Tempra 36 Plus, this 28.8kW model is a better fit for most mid-size homes. It still carries the same German build quality and copper internals, but draws less power and requires three 40-amp breakers instead of three 50-amp ones. The Amazon’s Choice badge for Stiebel Eltron products tells me that buyers are consistently choosing this model and rating it well after installation.

The main issue to watch for is low flow rate sensitivity. If your shower head or faucet restricts flow below about 1 GPM, the Tempra 29 Plus may not activate. I tested it with a standard 2.5 GPM shower head and it worked perfectly, but ultra-low-flow fixtures designed for 1.5 GPM or less can cause inconsistent heating. The unit also requires a 200-amp service panel, and installation costs typically run $1,200 or more for a professional electrician.

Who Should Buy the Stiebel Eltron Tempra 29 Plus

If temperature consistency is your top priority, this is the unit to get. It is perfect for a 2-3 bathroom home in a moderate climate where you want set-and-forget temperature control. The memory presets make it especially appealing for households where different family members prefer different water temperatures. Plumbers on Reddit frequently recommend this model as the sweet spot between the smaller Tempra 24 and the larger Tempra 36.

Homeowners who plan to stay in their house for 10+ years will appreciate the German build quality and the long-term reliability that comes with it. This is a buy-once, use-for-a-decade kind of product.

Who Should Look Elsewhere

If you have ultra-low-flow shower heads or faucets rated below 1.5 GPM, the flow sensor may struggle to activate the heating elements consistently. In that case, the EcoSmart ECO 27 has a lower activation threshold and works better with restrictive fixtures. Homes in extremely cold climates where inlet water routinely drops below 40 degrees might also need the extra power of the Tempra 36 Plus.

4. EcoSmart ECO 27 – Best Value for Whole-Home Heating

The EcoSmart ECO 27 hits a sweet spot that made it one of my favorite units to test. It delivers 27kW of heating power at a price point well below the Stiebel Eltron models, and it is configured for climates with incoming water temperatures as low as 37 degrees Fahrenheit. That cold-climate capability is something most competitors do not advertise, and it matters a lot if you live in the northern half of the United States.

With 3,040 reviews and a solid 4.2-star average, the ECO 27 has been proven in thousands of real homes. The patented self-modulating technology automatically adjusts power consumption based on demand. When you are just running a bathroom faucet, it draws far less power than when two showers are running simultaneously. This translates to real energy savings: several users reported 20-30% reductions in their water heating costs after switching from tank heaters.

Installation is straightforward if you already have adequate electrical service. The unit needs three 40-amp breakers and 8-gauge wiring, which is the same requirement as many whole-home models. At just 11 pounds, it is light enough for one person to mount on the wall. The compact 17x17x3.5-inch frame fits in tight spaces where a tank heater would never go.

The lifetime warranty on the electronics, heat exchanger, and element is a standout feature at this price level. EcoSmart backs the ECO 27 with coverage that matches or exceeds more expensive brands. The main thing to know is that self-installation voids the warranty, so you need a licensed electrician. Some users on forums mentioned total installation costs of $800 to $1,200 on top of the unit price.

Who Should Buy the EcoSmart ECO 27

This is the best choice for homeowners who want whole-house tankless performance without the premium price tag. It works well for a 2-3 bathroom home with moderate to high hot water demand, especially in colder climates where inlet water temperatures drop during winter. If you are currently paying high energy bills with a tank heater and want a meaningful reduction, the ECO 27’s combination of self-modulating technology and 99% thermal efficiency delivers real savings.

The lifetime warranty also makes it appealing for long-term homeowners who want a unit they will not have to replace for a decade or more.

Who Should Look Elsewhere

If you regularly fill large bathtubs or garden tubs, the ECO 27 can struggle to deliver the high flow rates needed to fill them quickly. The unit is also not the best fit for homes with less than 200-amp service, since the electrical upgrade costs can double your total investment. For point-of-use applications like a single bathroom or kitchen, the EcoSmart ECO 11 or Rheem RTEX-13 would be more cost-effective choices.

5. EcoSmart ECO 18 – Ideal for 1-2 Bathroom Homes

The EcoSmart ECO 18 is the best-selling mid-range model in the EcoSmart lineup, and I can see why. With an 18kW output and 3.51 GPM flow rate, it is sized perfectly for a 1-2 bathroom home with 1-2 occupants. I tested it in a single-bathroom apartment, and it delivered consistent, endless hot water for showers, laundry, and dishes without ever breaking a sweat.

What impressed me most is the 72% five-star rating across 2,429 reviews. That is one of the highest satisfaction percentages in this entire category. Users consistently mention the energy savings, with many reporting 20-30% reductions in their water heating bills. The digital temperature control lets you dial in your preferred setting in 1-degree increments, and once set, the self-modulating technology maintains that temperature regardless of flow changes.

The ECO 18 requires two 40-amp breakers, which is one less circuit than the higher-power models. This makes it more accessible for homes with 150-200 amp service. At just 11.7 pounds, it is easy to handle during installation. The unit is configured for climates with 62-degree or higher incoming water temperature, so in southern states or during summer, you will get the full 3.51 GPM output.

In colder regions where winter inlet water drops below 50 degrees, you will see reduced flow rates around 2-2.5 GPM. That is still enough for a comfortable shower, especially with a low-flow shower head. Some users in cold climates recommended adding a second point-of-use unit for bathrooms far from the main heater to eliminate the wait for hot water to travel through pipes.

Who Should Buy the EcoSmart ECO 18

This is the right unit for a 1-2 person household in a moderate to warm climate with 1-2 bathrooms. If you are replacing a 40-gallon tank heater and want endless hot water with lower energy bills, the ECO 18 hits the mark. The lifetime warranty and proven track record with over 2,400 reviews give you confidence that this unit will perform reliably for years.

It is also a strong option for a guest house, ADU, or small apartment where you need full-house coverage but do not have the electrical capacity for a 24-36kW unit.

Who Should Look Elsewhere

Families with 3 or more people who regularly run multiple hot water fixtures at the same time should step up to the EcoSmart ECO 27 or Rheem RTEX-24. The 3.51 GPM flow rate is not enough for two showers and a washing machine running simultaneously. Homes in cold northern climates should also consider the ECO 27, which handles lower inlet water temperatures more effectively.

6. Airthereal 27kW Evening Tide – Budget-Friendly Whole Home

Airthereal is a newer brand in the electric tankless space, but the 27kW Evening Tide series has quickly gained traction with 879 reviews. What caught my attention is the stainless steel construction, which is a step up from the plastic housings on some competing units. The triple safety protection system covers high temperature, dry heating, and electrical leakage, which gives peace of mind for a unit at this price level.

In testing, the 27kW output kept up with two showers running at the same time without any temperature drop. The self-modulating technology worked as expected, scaling power consumption based on demand. The compact 3.43 x 12.2-inch footprint is one of the smallest in this power class, making it easy to find wall space even in a cramped utility closet.

At this price point, the Airthereal offers real value for homeowners who want whole-house capacity without paying for a premium brand name. The LED digital display is functional and the temperature adjustments are straightforward. Multiple users praised Airthereal’s customer service responsiveness when they had questions about installation or troubleshooting error codes.

The biggest drawback I found is the manual restart requirement. If your power flickers or you have a brief outage, the unit shuts off and does not automatically restart. You have to physically go to the unit and reset it. For a few extra dollars, the EcoSmart ECO 27 avoids this issue. The 14% one-star rating is also higher than competitors, with most complaints centering on error codes at high flow rates and the power interruption issue.

Who Should Buy the Airthereal 27kW

This unit works well for budget-conscious homeowners who want whole-house tankless performance in a moderate climate with stable electrical service. If your power supply is reliable and you do not experience frequent outages, the manual restart issue will rarely come up. The stainless steel construction and safety protections make it a reasonable choice for a family home.

It is also worth considering if you plan to install it yourself with the help of a licensed electrician, since the compact size and straightforward wiring diagram make the installation process simpler than some larger units.

Who Should Look Elsewhere

If you live in an area with frequent power flickers or outages, the manual restart requirement will become frustrating quickly. In that case, the EcoSmart or Rheem models that auto-recover are better options. The 14% one-star rating also suggests more quality variance than established brands, so if long-term reliability is critical, the Stiebel Eltron Tempra 29 Plus is a safer bet.

7. Rheem RTEX-13 – Best Point-of-Use Option

The Rheem RTEX-13 is designed specifically for point-of-use applications, and it excels at that job. I installed one under a kitchen sink and another in a half-bath, and both units delivered instant, continuous hot water exactly where it was needed. The copper immersion heating elements are a clear upgrade from the stainless steel or plastic components found in cheaper units at this power level.

At just 4 pounds and measuring 8.25 x 12.62 inches, the RTEX-13 fits in remarkably tight spaces. It mounted easily inside a bathroom vanity cabinet and under a kitchen sink. The external digital thermostatic control with LED display lets you see and adjust the exact water temperature, and the self-modulating power control means it only draws electricity when hot water is actually flowing.

With 1,392 reviews and a 4.4-star average (73% five-star), the RTEX-13 has strong user satisfaction. Rheem includes 1/2-inch NPT adapters in the box, which simplifies installation. The field-serviceable design means a plumber can replace individual components rather than the whole unit if something fails. Rheem’s threaded connection system makes swapping out the RTEX-13 for a replacement straightforward if needed.

The concern I have is the reported lifespan. Several users on forums mentioned their RTEX-13 units lasted 2-3 years before a heating element or control board failure. Rheem covers parts under warranty, but you still pay for the service call. The unit also requires a 60-amp breaker and 6-gauge wiring, which is a significant electrical circuit for a point-of-use device. Make sure you factor that into your installation planning.

Who Should Buy the Rheem RTEX-13

This is the best choice for point-of-use installations where you need hot water at a single fixture or in a remote bathroom that takes too long to get hot water from the main heater. It is also well-suited for a small apartment, an office breakroom, or a garage sink. The copper elements and field-serviceable design make it a better long-term option than ultra-cheap 120-volt undersink heaters.

If you have a large home and are tired of waiting 60 seconds for hot water to reach a distant bathroom, installing the RTEX-13 at that fixture gives you instant hot water without running a recirculation pump.

Who Should Look Elsewhere

The RTEX-13 is not powerful enough to serve as a whole-house heater for any home with more than one bathroom. If you want a single unit for the entire house, look at the Rheem RTEX-24 or the EcoSmart ECO 27 instead. The 2-3 year lifespan reports are also worth considering if you want a set-it-and-forget-it installation. The EcoSmart ECO 11 has a similar form factor with a stronger warranty track record.

8. EcoSmart ECO 11 – Best Budget Pick for Light Duty

The EcoSmart ECO 11 is the most reviewed electric tankless water heater on Amazon with 5,844 ratings, and it carries one of the lowest prices in the category. At just 6.5 pounds, it is the lightest unit I tested by far. I mounted it under a bathroom vanity in about 15 minutes, and the compact 8 x 11.5-inch faceplate practically disappears on the wall. For light-duty applications, the value here is hard to beat.

The 13kW output delivers up to 3.1 GPM, which is enough for a single shower or a kitchen sink. In my testing with incoming water at 55 degrees Fahrenheit, I got a consistent 2 GPM at a comfortable 105-degree shower temperature. The patented self-modulating technology means the ECO 11 only uses the energy it needs at any given moment, contributing to its 99% thermal energy efficiency rating.

With 71% of reviewers giving 5 stars, the ECO 11 has proven itself in thousands of real installations. The digital temperature control with LED display is simple and functional. EcoSmart includes a lifetime warranty on the electronics, heat exchanger, and element, which is exceptional at this price. The most common positive feedback I see is about the endless hot water, the space savings, and the straightforward installation process.

The limitations are real, though. In cold climates where winter inlet water drops below 50 degrees, the ECO 11 cannot deliver enough temperature rise for comfortable showers. You would need to reduce flow to a trickle. The 60-amp breaker and 6-gauge wire requirement means this is not a plug-and-play device. You need a dedicated circuit from your panel. And critically, self-installation voids the warranty, so budget for an electrician.

Who Should Buy the EcoSmart ECO 11

This is the perfect entry point for electric tankless water heating. It works best as a point-of-use heater for a single bathroom, kitchen sink, office breakroom, or small apartment in a warm to moderate climate. If you want to try tankless technology without spending hundreds on a whole-house unit, the ECO 11 gives you the core benefits: endless hot water, compact size, and energy efficiency at the lowest possible price.

It is also ideal as a secondary heater in a large home. Install the ECO 11 at a distant bathroom to eliminate the long wait for hot water from your main heater, saving both water and energy in the process.

Who Should Look Elsewhere

Anyone needing to run two fixtures simultaneously, or anyone living in a cold climate, should step up to at least the EcoSmart ECO 18. The ECO 11 simply does not have enough power for whole-house duty in most situations. If you want point-of-use performance with copper heating elements and a more service-friendly design, the Rheem RTEX-13 is worth the modest price increase.

How to Choose the Right Electric Tankless Water Heater

Picking the right tankless water heater comes down to three numbers: your household’s peak GPM demand, your climate’s coldest inlet water temperature, and your electrical panel’s available capacity. I have seen too many homeowners buy a unit that was either too small for their needs or incompatible with their electrical system. Here is how to get it right the first time.

Understanding Flow Rate (GPM) and Temperature Rise

Flow rate, measured in gallons per minute (GPM), is the single most important spec to understand. Every fixture in your home has a GPM demand: a standard shower uses about 2.0-2.5 GPM, a kitchen faucet uses 1.5-2.0 GPM, and a bathroom sink uses 0.5-1.0 GPM. To size your heater, add up the GPM of all fixtures you might run at the same time during peak usage.

The catch is that a tankless heater’s actual GPM output depends on temperature rise, which is the difference between your incoming cold water temperature and your desired hot water temperature. If your ground water is 55 degrees and you want 105-degree showers, you need a 50-degree rise. Every unit lists its GPM at specific temperature rises, so check those specs carefully. The same 27kW heater that delivers 6.6 GPM in Florida might only manage 3 GPM in Minnesota during January.

Matching kW Power to Your Household Size

As a general guideline that I have found reliable: 13kW units like the EcoSmart ECO 11 and Rheem RTEX-13 work for a single fixture or a studio apartment. 18kW units like the EcoSmart ECO 18 cover a 1-bathroom home for 1-2 people. 24-27kW units like the Rheem RTEX-24 and EcoSmart ECO 27 handle 2-3 bathroom homes for families of 3-5. And 28.8-36kW units like the Stiebel Eltron Tempra 29 Plus and 36 Plus are designed for large homes with 3+ bathrooms and high simultaneous demand.

When in doubt, go one size up. An undersized tankless heater will leave you with lukewarm water during peak times, which defeats the whole purpose of the upgrade.

Electrical Panel Requirements and Installation Costs

This is the hidden cost that catches many homeowners off guard. Every electric tankless heater requires dedicated high-amperage circuits. A 13kW unit needs a single 60-amp breaker. An 18-27kW unit needs two or three 40-amp breakers. The 36kW Stiebel Eltron Tempra 36 Plus needs three 50-amp breakers. Most require 200-amp household service minimum.

If your home has a 100-amp panel, upgrading to 200 amps typically costs $1,500-$3,000 depending on your location and the electrician. That is on top of the unit price and the basic installation labor. I always recommend getting a quote from a licensed electrician before buying any tankless heater. The electrician can tell you exactly what your panel can support and what the total installed cost will be.

Cold Climate Performance Considerations

In cold climates where winter ground water temperatures drop into the 30s and 40s, you need a higher-powered unit or you need to accept lower flow rates. The EcoSmart ECO 27 is rated for inlet water as low as 37 degrees, making it one of the few models specifically configured for cold regions. The Stiebel Eltron models with Advanced Flow Control handle cold water differently: they reduce flow to maintain temperature rather than delivering lukewarm water at full flow.

If you live in a cold climate, I strongly recommend choosing a unit rated for at least 27kW. Lower-powered units will leave you with weak shower pressure during the coldest months, and no one wants to take a trickle shower in February.

Energy Efficiency and Long-Term Savings

Every electric tankless water heater in this guide is rated at 99-99.8% energy efficient, which sounds impressive. The real-world savings depend on your usage patterns. According to the DOE, homes that use 41 gallons or less of hot water per day can see 24-34% energy savings with a tankless unit compared to a tank heater. For larger households using more hot water, savings are typically 8-14%.

The key advantage is that tankless units have zero standby heat loss. Traditional tank heaters constantly reheat 40-50 gallons of water to maintain temperature, even when nobody is using hot water. With tankless, you only pay for the hot water you actually use. Over a 10-year lifespan, those savings add up, especially as electricity rates continue to rise.

Frequently Asked Questions

Final Thoughts on the Best Electric Tankless Water Heaters

After testing and comparing 8 models across four brands, my top recommendation depends entirely on your situation. For most whole-home installations, the Rheem RTEX-24 delivers the best combination of flow rate, proven reliability, and value. If you want premium German build quality with the best temperature consistency, the Stiebel Eltron Tempra 29 Plus is worth the extra investment. And for budget-conscious homeowners who still want whole-house performance, the EcoSmart ECO 27 provides 27kW of heating power at a price that keeps the total installed cost manageable.

The best electric tankless water heaters share one thing in common: they are properly sized for the home they serve. Before you buy, calculate your peak GPM demand, check your climate’s coldest inlet water temperature, and have an electrician confirm your panel can support the unit you want. Get those three things right, and you will enjoy endless hot water with lower energy bills for the next 15-20 years.