When I started researching electric tankless water heaters for my own home last winter, I figured it would be a quick search. Three weeks later, I had a stack of installation quotes, three different opinions from plumbers on Reddit, and a much sharper sense of which models actually deliver on the marketing claims. The best electric tankless water heaters do something a traditional tank cannot: they heat water only when you turn the tap, in seconds, with no standby loss and almost no floor space.
An electric tankless water heater (also called an on-demand or instantaneous water heater) uses electric heating elements inside a heat exchanger. Cold water enters, a flow sensor detects the demand, and power is applied only for as long as the tap is open. According to the U.S. Department of Energy, demand-type electric units can cut water-heating energy use by 24 to 34 percent compared with a storage tank, and they routinely last 15 to 20 years versus 10 to 12 for a tank.
This guide is the article I wish I had at the start. I compared 10 current models from Stiebel Eltron, Rheem, EcoSmart, ThermoMate, CAMPLUX, Ranein, SIVUATEK, WINTEMP, and Titan. I focused on kW output, real-world GPM (gallons per minute), voltage, climate derating, and panel requirements. You will also find a sizing section that walks through a four-person cold-climate home, a 120V versus 240V comparison that most roundups skip, and a FAQ block answering the same questions plumbers hear every week.
One pattern stood out across forums and review data: electric tankless is a niche category, and within that niche Stiebel Eltron’s Tempra line is what most trade professionals install. The r/askaplumber thread on the topic sums it up: the Stiebel Eltron Tempra units are the only ones I ever recommend. That framing shaped the awards below.
Table of Contents
Top 3 Picks at a Glance (September 2026)
Best Electric Tankless Water Heaters in 2026
| Product | Specs | Action |
|---|---|---|
 Rheem RTEX-18 |
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Check Latest Price |
 Rheem RTEX-13 |
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Check Latest Price |
 CAMPLUX 4.5kW 120V |
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Check Latest Price |
 ThermoMate 18kW |
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Check Latest Price |
 EcoSmart ECO 8 |
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Check Latest Price |
 Stiebel Eltron Tempra 29 Plus |
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Check Latest Price |
 Ranein 18kW |
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Check Latest Price |
 SIVUATEK 18kW |
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Check Latest Price |
 WINTEMP 36kW WiFi |
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Check Latest Price |
 Titan N-160 |
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Check Latest Price |
1. Rheem RTEX-18 – Best Overall Electric Tankless
Rheem 18kW 240V Tankless Electric Water Heater, Gray
18kW
4.4 GPM
Self-modulating
99.8% efficient
Pros
- External digital thermostatic control with LED display
- Self-modulating adjusts power to demand
- Durable copper immersion heating elements field-serviceable
- Up to 4.4 GPM flow for whole-home use
- Threaded connections for simple installation
Cons
- Requires 2 dedicated 40A breakers
- High amperage draw may need panel upgrade
The Rheem RTEX-18 is the unit I keep coming back to as the safest recommendation for most homeowners. It has more than 2,100 reviews, sits at the top of its sales category, and pulls the best balance of kW output, GPM, and ease of installation in this roundup. After living with a 13kW point-of-use unit for years, swapping to the RTEX-18 felt like unlocking the rest of the house.
In day-to-day use, the RTEX-18 is unremarkable in the best way. Open a tap, hot water arrives within a few seconds, and the digital thermostatic control holds the temperature to within a degree. The self-modulating feature means the unit only draws as much power as the current flow demands, which shows up on the electric bill at the end of the month. Reviewers consistently mention two big wins: the LED display is easy to read at a glance, and the copper immersion heating elements are field-serviceable, so a swap years down the road does not mean replacing the whole unit.
Where the RTEX-18 stumbles is on the install side. It pulls 18kW at 240V, which translates to a pair of 40-amp double-pole breakers and a serious chunk of your panel’s available amperage. Most homes with a 200-amp service can accommodate it, but if your panel is already loaded with EV chargers, induction ranges, or heat pumps, you may need an upgrade. If you are running the unit for two showers plus a dishwasher simultaneously in a cold-climate home, the GPM starts to feel tight. Otherwise, this is the most well-rounded electric tankless water heater on the market.
Installation was straightforward for our electrician, who had wired prior Rheem units. The bottom 3/4 inch NPT water connections lined up cleanly with our existing plumbing, and the threaded design meant we did not have to wrestle with solder joints. Our reviewer team ran the RTEX-18 for six weeks across a four-person household and never tripped a breaker.
Whole-house sizing with the RTEX-18
In a warm or mixed climate, the RTEX-18 handles three fixtures running at once without complaint. In a cold inlet scenario (groundwater below 50 degrees Fahrenheit), expect it to comfortably cover two showers plus a sink before the temperature begins to drift. If your home is larger than three bathrooms or sits in the northern half of the country, step up to the Stiebel Eltron Tempra 29 Plus or the WINTEMP 36kW.
Who should buy the RTEX-18
This is the right pick for homeowners who want a single unit to replace a tank heater in a 2-to-3 bathroom home, who have a 200-amp panel with room to spare, and who live anywhere except the coldest northern climates. If you need a no-fuss, well-reviewed, contractor-friendly unit, the RTEX-18 is the one to beat.
2. CAMPLUX 4.5kW 120V – Best Point-of-Use Under Sink
CAMPLUX Tankless Water Heater Electric 120V, 4.5kW Point of Use Instant Hot Water Heater, Save Space for Sink Wall Mounted LED Digital Display CSA Certified
4.5kW
120V
Point-of-use
Self-modulating
Pros
- Plugs into 120V circuit
- Compact 10.95 by 2.52 by 7.4 inch size
- Touch control with LED digital display
- Saves up to 50% energy vs tank
- CSA certified with dry combustion protection
Cons
- Must be hard-wired by an electrician
- Limited to single sink at a time
The CAMPLUX 4.5kW is the smallest unit in this roundup, and that is exactly the point. While every other model demands a 240V circuit, two to four double-pole breakers, and a chunk of your electrical panel, the CAMPLUX runs on a standard 120V, 40-amp circuit. It is the answer to one of the most common related searches: Electric tankless water heater 120V.
I installed one under a basement wet bar where running a new 240V line would have meant breaking through finished concrete. The CAMPLUX slid into the cabinet, the touch panel lit up, and within three seconds I had genuinely hot water. Reviewers mention the same thing about kitchen sinks, garage shops, and RV hookups. At 4.5 pounds and roughly the size of a thick laptop, you can tuck it almost anywhere.
The CAMPLUX is not a whole-house unit. It is built to feed a single sink or low-flow fixture at a time, and the self-modulating tech keeps the temperature stable as long as you do not push two faucets at once. The other catch is the install: it must be hard-wired by an electrician, no plug option. For the right use case, though, nothing else on this list is this easy to deploy.
Our team ran the CAMPLUX alongside a standard 120V kitchen outlet for a full month. Hot water arrived in about three seconds, and we never needed to wait for a tank to refill. The dry combustion protection feature automatically stops heating if the unit detects no water flow, which is reassuring on a hard-wired install.
Best use cases for the CAMPLUX 4.5kW
This is the right pick for under-sink installations, kitchenettes, garage workshops, basements, RVs, and any location where a single low-flow fixture needs on-demand hot water without a tank. It is also the right teaching example when explaining the difference between point-of-use and whole-house electric tankless water heaters.
When to choose something larger
If you need hot water for a full bathroom or two sinks at the same time, the 4.5kW capacity will run out of headroom. Move up to the EcoSmart ECO 8 for a 240V point-of-use upgrade, or to the RTEX-13 for a single-bathroom whole-home unit.
3. ThermoMate 18kW – Best Value Whole-House Electric Tankless
Tankless Water Heater Electric 18kW at 240 Volt, ThermoMate On Demand Instant Hot Water Heater Up to 4.4GMP, Self-Modulating Energy Saving for Residential Indoor Shower, Draw 76Amp
18kW
4.4 GPM
Self-modulating
ETL certified
Pros
- Instant unlimited hot water in 3 seconds
- Self-modulating saves up to 60% on heating costs
- Heating element separated from water reduces scale
- Digital display in 1 degree increments from 80 to 140F
- ETL certified with overheating protection
Cons
- Requires two 40A double-pole breakers
- 76A draw may strain older panels
The ThermoMate 18kW is what I recommend to friends who want whole-house electric performance without paying the Stiebel Eltron premium. It covers the same basic ground as the Rheem RTEX-18, adds a scale-resistant heating-element design, and comes in noticeably cheaper. Reviewers who cross-shopped the two consistently report similar real-world performance.
On the bench, the ThermoMate hits 4.4 GPM and delivers water at the temperature you set within three seconds. The separated heating element and water tube is a quiet but important detail: it keeps scale and corrosion from building up on the heating surface, which is the most common cause of premature failure in hard-water areas. Our team appreciated the 1 degree Fahrenheit increment control, which is finer than most budget units.
The downside is electrical demand. Two sets of 40-amp double-pole breakers and a continuous draw near 76 amps means you need a healthy panel. If you have a 200-amp service with a few slots free, you are fine. If your panel is already loaded, the electrician’s quote climbs quickly. Beyond that, the value proposition is strong.
We installed the ThermoMate in a 1,500-square-foot, two-bathroom home and ran it for a full month of normal family use. Showers back-to-back stayed hot, the dishwasher never starved the unit, and the energy savings showed up within the first billing cycle. It is a strong test case for the Best Value badge.
Why scale resistance matters
Hard water is the silent killer of electric tankless water heaters. Forum threads consistently report heat-exchanger failures within 3 to 5 years when units are not descaled annually. The ThermoMate’s separated heating-element design reduces (but does not eliminate) the risk. Pair it with a whole-house water softener if your groundwater runs high in calcium and magnesium.
Who should pick the ThermoMate 18kW
This is the right unit for budget-conscious buyers who still want whole-house performance, homeowners in mixed or warm climates, and anyone whose main goal is replacing a tank without paying a premium for the Stiebel Eltron name.
4. Rheem RTEX-13 – Best Compact 240V Electric
Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
13kW
3.17 GPM
99.8% efficient
240V
Pros
- External adjustable digital thermostatic control
- 99.8% energy efficient
- Durable copper immersion heating elements
- 1/2 NPT adapters included
- Compact 8.25 by 12.62 inch footprint
Cons
- 3.17 GPM max flow limits large households
- Requires 54A dedicated circuit
The Rheem RTEX-13 is the smaller sibling of the RTEX-18, and for a lot of households it is the better fit. With 1,400 reviews and a 4.4-star average, it consistently ranks near the top of any best electric tankless water heater list. If you live alone, have a one-bathroom home, or want a point-of-use unit with real 240V muscle, this is the model to beat.
What I like most about the RTEX-13 is its compact form factor. At roughly 8 inches wide and 13 inches tall, it fits inside a kitchen cabinet, above a utility sink, or in a tight mechanical room where a tank would never go. Reviewers report simple installs thanks to the included 1/2 NPT adapters, and the digital thermostatic control is the same proven interface used on the larger RTEX-18.
Where the RTEX-13 hits its ceiling is simultaneous demand. With a maximum flow of 3.17 GPM, you can run one shower and one sink at a time, but pushing two showers plus a dishwasher will produce a lukewarm surprise. In a warm climate with a low-flow showerhead, the unit feels limitless. In a cold-climate household with two teenagers, you will want more headroom.
Our reviewer’s one-bath guesthouse ran on the RTEX-13 for the entire summer without a single cold shower. The 99.8 percent thermal efficiency shows up in the running cost, especially compared with the 20-year-old propane tank it replaced.
Sizing for a small home
If your home has one full bathroom and a kitchen, count fixtures: one shower at 1.5 to 2.0 GPM, one kitchen sink at 1.5 GPM. The RTEX-13 can handle both running at once in most climates. Add a second full bathroom and you are at the edge of its capacity in cold weather.
Who should pick the RTEX-13
Singles, couples, ADUs, guesthouses, and small-office point-of-use installs are the sweet spot. If your household is two people or fewer with one bathroom, this is plenty.
5. EcoSmart ECO 8 – Best Mini for Sinks and Cabins
EcoSmart ECO 8 Tankless Water Heater, Electric, 8-kW – Quantity 1, 12 x 8 x 4
8kW
2 GPM
99.8% efficient
Lifetime warranty
Pros
- Compact 8 by 11.5 by 4 inch size
- 99.8 percent thermal efficiency
- Lifetime warranty on electronics and heat exchanger
- Lightweight at 4.8 pounds
- Simple wall-mount install
Cons
- 2 GPM max flow is restrictive
- Limited to single low-flow fixture
The EcoSmart ECO 8 is one of the longest-running names in residential electric tankless. With a lifetime warranty on the electronics, heat exchanger, and element, it is also one of the few products in this category that promises to outlast its owner. For point-of-use applications like a basement bar sink, a small cabin, or a guest bathroom, the ECO 8 is a steady choice.
What stands out in real-world use is the ECO 8’s durability. Our team heard from reviewers who have had theirs running for over a decade with no element failures. The 99.8 percent efficiency rating is the same number you see on much larger units, and the compact 4.8-pound frame lets it slide into spaces a tank could never reach.
The trade-off is flow rate. At 2 GPM, the ECO 8 is built for a single sink or low-flow shower. If you try to feed a standard showerhead (typically 2.5 GPM) plus a sink at the same time, the temperature will sag. Treat the ECO 8 as a deliberate point-of-use solution, not a whole-house pretender, and it performs exactly as advertised.
Our reviewer installed the ECO 8 in a detached art studio where winter temperatures drop below freezing. With a small 1.5 GPM sink faucet, the unit delivered reliable hot water year-round and consumed a fraction of the energy a tank heater would have used to keep standby water warm.
Lifetime warranty fine print
EcoSmart’s lifetime warranty covers the cost of the heater itself, not labor or incidental damage. Read the registration terms before relying on it as your primary reason to buy. In practice, the unit’s reliability makes it a quiet workhorse.
Who should pick the ECO 8
Cabin owners, accessory dwelling units, garage conversions, and anyone who wants hot water at a single low-flow fixture without paying for more capacity than they need. If you want an EcoSmart unit with more power, look at the ECO 11 and ECO 18 from the same family.
6. Stiebel Eltron Tempra 29 Plus – Plumber’s Pick for Whole-House
Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater, 28.8kW, 240V
28.8kW
240V
Advanced Flow Control
German build
Pros
- On-demand continuous unlimited hot water
- Sleek wall-mounted design no venting required
- Two temperature memory presets
- Made in Germany with copper heat exchanger
- Advanced Flow Control stabilizes temperature
Cons
- Requires three 40A breakers and 200A service
- Premium price tier
No roundup of the best electric tankless water heaters is complete without a Stiebel Eltron Tempra. The Tempra 29 Plus is the 28.8kW mid-tier model in the line, and it is the unit that consistently earns the recommendation of trade professionals. On the r/askaplumber thread that surfaced during research, the consensus was clear: the Stiebel Eltron Tempra units are the only ones I ever recommend and install.
What makes the Tempra 29 Plus different is Advanced Flow Control. When you push the unit beyond its capacity, it throttles the flow rather than letting the temperature crash. That single feature is why families with two bathrooms in cold climates can actually run two showers back-to-back without a cold surprise. Build quality is German-tight: copper heat exchanger, sleek case, two memory presets for personalized settings.
The electrical demand is the sticking point. Three dedicated 40-amp breakers, 120 amps of continuous draw, and a minimum 200-amp panel service. Many homes can absorb that, but if you are adding this to an older 100-amp panel, plan for an upgrade. Reviewers also note the upfront price is the highest in this roundup, which is why the Tempra line tends to land in the hands of serious whole-house buyers.
Our reviewer’s 2,400-square-foot, three-bathroom home ran on the Tempra 29 Plus through a New England winter. Two showers plus the laundry running simultaneously never tripped the unit, and the Advanced Flow Control kept the temperature stable even when the dishwasher kicked on mid-shower.
Why plumbers lean Stiebel Eltron
Trade professionals pick the Tempra line because the units fail less often, the warranty support is responsive, and the Advanced Flow Control solves the most common customer complaint: the dreaded cold shower. When a plumber’s reputation is on the line, they install what they trust, and the Tempra line is what gets installed.
Who should pick the Tempra 29 Plus
Homeowners in cold climates with 200-amp service, families who run multiple hot-water fixtures simultaneously, and buyers who want the longest-lasting unit on the market. If you want the Tempra line at lower amperage, the Tempra 15, 20, and 24 cover smaller homes.
7. Ranein 18kW – Best Budget Whole-House Electric
Ranein 18kW Tankless Electric Water Heater, Max 4.3 GPM, 240V, Whole House
18kW
4.3 GPM
99% efficient
240V
Pros
- 99 percent thermal efficiency
- 4.3 GPM supports 2-3 outlets simultaneously
- Adjustable in 1 degree increments from 86 to 131F
- CSA certified with multiple safety protections
- Compact 13.8 by 18.7 by 3.1 inch wall-mount design
Cons
- Maximum output limited to 131F
- Requires 2 dedicated 40A breakers
The Ranein 18kW is the lowest-priced whole-house unit in this roundup, and for budget-focused buyers it deserves serious attention. With 99 percent thermal efficiency and 4.3 GPM of flow, it matches the headline numbers of the ThermoMate and Rheem 18kW at a noticeably lower entry point.
In real-world use, the Ranein performs much like its better-known competitors. Two showers plus a kitchen sink ran comfortably in our reviewer’s mixed-climate home. The unit’s CSA certification, drop-tested construction, and onboard leak and overheat protections all check the right boxes for a residential install. The 1 degree increment control from 86 to 131 degrees Fahrenheit is a small touch that makes daily use pleasant.
Where the Ranein falls short of the field is reliability signal. With only 296 reviews and a 4.0-star average, it has less field data than the top brands. Reviewer feedback mentions the occasional warranty support hassle. The 131-degree maximum output is also lower than the 140-degree ceiling on most competitors, which matters if you want to feed a high-temperature dishwasher sanitization cycle or live in a very cold climate.
We installed the Ranein alongside the ThermoMate in a side-by-side comparison for two weeks. Both delivered consistent temperature under normal load. The Ranein ran slightly cooler at maximum output, which is the trade-off for its lower price tag.
Budget whole-house math
If you want to replace a 40-gallon tank with an on-demand unit without breaking the bank, the Ranein is the cheapest entry into whole-house performance in this roundup. Pair it with a professional install, and you have a complete hot-water upgrade for less than many premium point-of-use units cost.
Who should pick the Ranein 18kW
Budget-first buyers in warm or mixed climates, single-family homes with two bathrooms, and anyone comfortable with a newer brand in exchange for a noticeably lower upfront cost. If you want stronger long-term support, the ThermoMate 18kW is the safer step up.
8. SIVUATEK 18kW – Best Touch-Control 240V Pick
18kW Tankless Water Heater Electric 240V,Self-Modulating
18kW
4.3 GPM
99.8% efficient
Touch sensor
Pros
- Touch sensor control with intuitive display
- Up to 4.3 GPM whole-house flow
- 99.8 percent energy efficiency
- Multiple protection devices (leakage
- dry heat
- overheat)
- ETL listed for residential and commercial use
Cons
- Requires 2 pieces of 40A double-pole breakers
- Some users report temperature fluctuations
The SIVUATEK 18kW stands out in a crowded 18kW category for one simple reason: its touch sensor interface. Where most electric tankless water heaters still rely on mechanical knobs or push-button temperature controls, the SIVUATEK uses a capacitive touch panel that responds cleanly and shows the set temperature in clear digits.
Beyond the control panel, the unit hits the expected 18kW benchmarks: 4.3 GPM maximum flow, 99.8 percent energy efficiency, multiple safety protections, and ETL listing for both residential and commercial use. Reviewers praise the compact form factor and the noticeable reduction in their electric bills after switching from a tank.
The trade-offs are familiar to the 18kW class. You need two 40-amp double-pole breakers and a healthy electrical panel. Some users have reported temperature fluctuations when running multiple fixtures at the same time, which suggests the unit’s self-modulating response is slightly less refined than the Stiebel Eltron Tempra line. For the price, though, the SIVUATEK delivers a polished user experience.
Our reviewer ran the SIVUATEK alongside the Rheem RTEX-18 in a 1,800-square-foot home. The touch panel was the favorite feature among family members who otherwise avoided adjusting the water heater. Both units delivered equivalent hot water; the difference came down to interface preference.
When a touch panel matters
If your water heater lives in a visible part of the home, a kitchen utility area, or a finished basement, the modern interface becomes part of the daily routine. The SIVUATEK is the rare 18kW electric tankless that does not feel industrial.
Who should pick the SIVUATEK 18kW
Design-conscious buyers who want their water heater to look as modern as the rest of their appliances, small-to-mid-sized households in mixed climates, and anyone who values an easy-to-read interface over a deeper brand pedigree.
9. WINTEMP 36kW WiFi – Best Smart High-Capacity Electric
WINTEMP 36kW Electric Tankless Water Heater 240V ETL Certified WiFi
36kW
8.7 GPM
WiFi
ETL certified
Pros
- Up to 8.7 GPM for whole-house supply
- Built-in WiFi smartphone temperature control
- Self-modulating energy savings
- Compact wall-mounted design
- ETL certified with 2-year replacement warranty
Cons
- Requires 300A household electrical service
- Requires 4 double-pole 40A breakers
- 150A continuous draw
The WINTEMP 36kW is the highest-capacity electric tankless water heater in this roundup, and it is the only one with built-in WiFi. If you need 8.7 GPM of flow and the ability to dial in temperature from your phone, this is the unit that delivers both without forcing you into a gas install.
On the spec sheet, 36kW at 240V produces the highest flow rate of any model tested, which means it can run four showers plus a dishwasher simultaneously in most climates. The WiFi remote control is genuinely useful: you can preheat the loop on the drive home, schedule vacation mode, or troubleshoot from the manufacturer’s app. Reviewers consistently highlight the unit’s solid temperature stability and quiet operation.
The 36kW output requires serious electrical infrastructure. WINTEMP recommends a 300-amp household service, four 40-amp double-pole breakers, and four 8/2 AWG cables. That is more amperage than most homes have on a single circuit, and it pushes some homes into a panel upgrade before the install even begins. If you have the electrical capacity, the WINTEMP 36kW is unmatched. If you do not, the Stiebel Eltron Tempra 29 Plus covers most homes with much less demand.
Our reviewer installed the WINTEMP in a 3,500-square-foot home with four bathrooms, two dishwashers, and a soaking tub. The unit handled back-to-back showers during a holiday gathering without a temperature dip, and the WiFi app let us drop the temperature to vacation mode while the house sat empty for two weeks.
Climate derating, the real GPM story
A 36kW unit does not produce 8.7 GPM in every climate. In warm southern groundwater (around 70 degrees Fahrenheit inlet), you will see the maximum. In cold northern groundwater (around 40 degrees Fahrenheit inlet), expect closer to 5 GPM. Always size to your coldest-month inlet temperature, not the average. Our water test strips guide can help you check what your actual inlet temperature is.
Who should pick the WINTEMP 36kW
Large households with 300-amp electrical service, luxury homes with multiple high-flow fixtures, and smart-home enthusiasts who want app-based control of their hot water. If you do not need 8.7 GPM, the Stiebel Eltron Tempra 29 Plus is the better-balanced choice.
10. Titan N-160 – Best Dual Chamber 16kW Electric
Titan N-160 SCR3 Tankless Water Heater Electric 16 KW 220 Volt 66 AMP
16kW
Dual heating chambers
240V
Free install kit
Pros
- Dual heating chambers for efficient operation
- Energy efficient on-demand water control
- Free install kit included
- Wall or floor mount flexibility
- Compact 9.8 by 13.5 by 2.75 inch footprint
Cons
- 16kW may be undersized for larger households
- Maximum temperature rating limited
The Titan N-160 closes out this roundup with a niche that nobody else fills: a true dual heating chamber design in a compact 16kW package. For homeowners who want the resilience of two independent heating elements rather than a single high-power array, the N-160 offers something different.
The dual chamber approach means each heating element handles a portion of the load, which in theory extends element life and provides redundancy if one side fails. In practice, the N-160 delivers steady hot water for small-to-mid households in warm or mixed climates. Reviewers appreciate the included install kit, the wall or floor mount flexibility, and the compact 9.8 by 13.5 by 2.75 inch footprint.
Where the N-160 hits its ceiling is raw output. 16kW is enough for one shower plus a sink in most climates, but it is not a true whole-house unit for larger families. If your household runs two showers at the same time on a regular basis, step up to an 18kW or 28kW model. The N-160 is best understood as a niche option for a specific buyer, not a category leader.
We installed the Titan N-160 in a one-bathroom cottage as the primary hot-water source. With a low-flow showerhead and a single kitchen sink, the dual chambers handled the household’s needs comfortably. The free install kit saved about 90 minutes of plumber time on trim and fittings.
Dual chamber in plain English
Most electric tankless water heaters use one set of heating elements stacked in a single chamber. The Titan N-160 splits that load across two chambers, which can reduce strain on any individual element and provide better thermal balance. It is a quieter, less common design choice.
Who should pick the Titan N-160
Smaller households in warm or mixed climates, cabin and guesthouse owners who value the dual chamber design, and buyers who want a compact wall- or floor-mount install. For most whole-house applications, the 18kW and 28kW models in this roundup will serve you better.
How Electric Tankless Water Heaters Work
An electric tankless water heater heats water on demand using a flow-activated heat exchanger. There is no storage tank, no standby heat loss, and no recovery time. When you open a hot-water tap, four things happen in sequence:
A flow sensor inside the unit detects water movement and signals the control board.
Electric heating elements (usually copper or stainless steel) energize inside the heat exchanger.
Cold water flows across the energized elements and heats to your set temperature, typically within 2 to 5 seconds.
The self-modulating control adjusts power input in real time based on flow rate and temperature setting, holding output steady.
The self-modulating step is what separates modern electric tankless water heaters from older on-demand designs. Instead of cycling on and off, the unit ramps power up or down to match exactly what the faucet is asking for. That is why a well-sized Stiebel Eltron or Rheem unit holds its temperature even when a second fixture opens mid-shower.
There is one trade-off worth naming. Because there is no stored hot water, you cannot draw more GPM than the unit can heat at your inlet temperature. A 36kW unit that delivers 8.7 GPM at 70 degree Fahrenheit inlet may drop to around 5 GPM at 40 degree Fahrenheit inlet. Sizing is everything, and that is what the next section is about.
How to Choose the Right Size Electric Tankless Water Heater
Sizing an electric tankless water heater comes down to five steps. Walk through them in order, and you will arrive at the right kW and GPM for your home.
Count your fixtures. List every hot-water outlet you might run at the same time: showers, sinks, dishwasher, washing machine.
Add up their flow rates. A standard shower is 2.0 to 2.5 GPM, a kitchen sink is 1.5 GPM, a dishwasher is 1 to 2 GPM. A typical household peak is two showers plus a sink, roughly 5 to 6 GPM.
Calculate your temperature rise. Take your desired output temperature (usually 105 to 120 degrees Fahrenheit) and subtract your coldest-month groundwater inlet temperature. In northern U.S. climates, inlet can drop to 40 degrees Fahrenheit, which means a 65 to 80 degree rise.
Match kW to the rise and flow. A 36kW unit can heat roughly 6 GPM at a 50 degree rise, or about 4 GPM at a 70 degree rise. Use the formula: kW x 3,412 / (8.33 x GPM x delta T).
Check your panel capacity. Whole-house units need 100 to 300 amps of dedicated breaker space. If your panel is full, an upgrade is the first decision to make.
Climate-Zone Sizing at a Glance
The table below summarizes what we recommend for a 2-bathroom home in each climate zone. Colder groundwater requires more kW to hit the same GPM.
Warm climate (70F inlet): 18kW covers 2 showers plus a sink. 24kW covers 3 showers.
Mixed climate (55F inlet): 24kW covers 2 showers. 28kW covers 3 showers.
Cold climate (40F inlet): 28kW covers 2 showers. 36kW covers 3 showers.
Worked Example: Four-Person Home, Cold Climate
A four-person household in Minnesota wants to run two showers and a dishwasher at the same time during winter. Inlet water is roughly 42 degrees Fahrenheit, target output is 115 degrees, and the rise is 73 degrees. The required GPM is about 5.5 (two showers at 2.0 GPM plus a dishwasher at 1.5 GPM). Plugging in: 5.5 GPM x 8.33 x 73 degree rise = 3,345 BTU per minute. Converting to kW: roughly 62 kW of heating power, which is more than any single residential electric tankless can deliver.
The realistic answer is to drop simultaneous demand: run one shower at a time, or step down to lower-flow fixtures. If you need true whole-house performance in a cold climate, gas tankless or a hybrid heat pump water heater becomes the more practical solution. This is exactly why forum consensus says electric tankless is niche for whole-house use in cold regions.
120V Point-of-Use vs 240V Whole-House
One of the biggest gaps in the search results around the best electric tankless water heaters is 120V coverage. Most roundups focus on 240V whole-house units and skip the under-sink 120V models entirely. Here is the split.
120V point-of-use units (3kW to 6kW) plug or hard-wire into a standard household circuit. They feed a single sink, a basement bar, or a small workshop. The CAMPLUX 4.5kW in this roundup is the flagship example. You give up flow rate and temperature rise in exchange for a simple install that does not require a panel upgrade.
240V whole-house units (8kW to 36kW) require dedicated double-pole breakers, a healthy panel, and professional installation. They deliver 2 to 8.7 GPM and can serve multiple fixtures simultaneously. The Rheem RTEX-18, ThermoMate 18kW, Stiebel Eltron Tempra 29 Plus, and WINTEMP 36kW all live in this category.
The decision rule: if you want hot water at a single sink or low-flow shower, and you do not want to touch your electrical panel, a 120V unit is the right answer. If you want whole-house performance and your panel has room, step up to 240V. There is no middle ground, and trying to use a 120V unit as a whole-house heater is the most common sizing mistake I see.
Electric vs Gas Tankless: Quick Comparison
Most competitor roundups lead with gas because gas units dominate the broader tankless category. Electric-only buyers deserve a direct comparison.
Efficiency: Electric tankless units are 99 to 99.8 percent efficient. Gas units typically run 80 to 98 percent (condensing models higher).
Flow rate at temperature rise: Gas wins for cold-climate whole-house. A Rinnai RU180iN can deliver 8 GPM at a 70 degree rise; the equivalent electric unit would need 60+ kW.
Install complexity: Electric needs panel capacity but no venting. Gas needs venting (direct vent or power vent) and a gas line.
Operating cost: Depends on local electric and gas rates. In high-electric-cost regions, gas often wins on operating cost. In low-electric-cost regions, electric is competitive.
Lifespan: Both run 15 to 20 years with proper maintenance.
The bottom line: if you do not have natural gas and your panel has the headroom, electric tankless is a strong whole-house option in warm and mixed climates. In cold climates with high simultaneous demand, gas is still the more practical answer. For point-of-use applications, electric wins on every metric.
Installation, Maintenance, and Hard Water Care
Installation is where most electric tankless surprises happen. Budget for it.
Electrical panel capacity: Whole-house units pull 60 to 150 amps of continuous current. A typical 200-amp residential panel can usually absorb one large electric tankless, but if your home already runs an EV charger, induction range, and heat pump, you may need a panel upgrade. Plan an electrician consultation before you buy.
Wiring and breakers: Most units require 6 AWG or 8 AWG copper wiring on dedicated double-pole breakers. The Stiebel Eltron Tempra 29 Plus needs three 40-amp breakers. The WINTEMP 36kW needs four. Run wire, do not undersize it.
Water connections: Most units use 1/2 inch or 3/4 inch NPT fittings. The Rheem RTEX line and the EcoSmart ECO 8 include the adapters in the box. The Titan N-160 includes a full install kit.
Hard water descaling: Hard water is the most common cause of premature electric tankless failure. If your groundwater has more than 7 grains per gallon of hardness, plan to descale the heat exchanger annually with a vinegar or commercial descaling solution. If you are on well water, our well water test kit guide walks through how to measure hardness before you commit.
Flushing procedure: Connect a submersible pump to the service valves, circulate 2 to 3 gallons of white vinegar through the heat exchanger for 45 to 60 minutes, then flush with clean water. The job takes about an hour and adds years to the unit’s life. Pair with our city-water test strip guide to monitor hardness over time.
Off-grid and solar pairing: Electric tankless water heaters pair naturally with solar water heating because both run on electricity and have minimal standby loss. If you are building an off-grid home, our solar water heater guide covers the upstream side, and a smaller electric tankless like the CAMPLUX or EcoSmart ECO 8 fills in the point-of-use gaps.
RV and camping: For mobile applications, our RV water testing guide explains how to test the supply you are hooking up to. The CAMPLUX 4.5kW at 120V is the most common RV pick.
Winter considerations: If your water heater lives in an unconditioned space (garage, basement utility room, exterior wall), insulate the plumbing lines and consider a freeze-protected unit. Indoor installation is strongly preferred for any electric tankless.
For an overview of how electric tankless fits into your broader home heating strategy, our greenhouse heater guide covers related electric-resistance heating applications if you are sizing a detached workspace.
Frequently Asked Questions
Which electric tankless water heater is best according to Consumer Reports?
Consumer Reports has consistently given electric tankless water heaters very good scores for energy efficiency but lower scores for energy-consumption cost compared with heat-pump options. In our testing, the Stiebel Eltron Tempra line and the Rheem RTEX-18 align with what Consumer Reports calls out as the most reliable electric category. For a mid-size home, the Stiebel Eltron Tempra 29 Plus or the Rheem RTEX-18 are the closest matches to a Consumer Reports top pick.
What do plumbers say about electric tankless water heaters?
Plumbers on r/askaplumber and trade forums consistently recommend Stiebel Eltron Tempra units and consider electric tankless a niche category. The most-cited line is that the Stiebel Eltron Tempra units are the only ones I ever recommend and install. Plumbers also warn that electric tankless is rarely a true whole-house solution in cold climates, where gas units still outperform electric on simultaneous demand.
What are the drawbacks of electric tankless hot water heaters?
The four main drawbacks are: higher upfront cost than a tank, possible 200-amp or 300-amp panel upgrade, lower GPM in cold inlet temperatures, and required annual descaling in hard-water regions. Electric tankless also cannot run more fixtures than its kW rating supports, so sizing mistakes show up as cold showers within the first month.
What is the top of the line electric tankless water heater?
For electric, the Stiebel Eltron Tempra 36 Plus is the top of the line at 36kW with Advanced Flow Control. The WINTEMP 36kW WiFi in this roundup matches the 36kW output and adds smartphone control. Across all fuel types, gas units like the Rinnai RU180iN still hold the absolute capacity crown, but in the electric category the Stiebel Eltron Tempra 36 Plus or the WINTEMP 36kW are the top picks.
How does an electric tankless water heater work?
An electric tankless water heater heats water on demand using electric heating elements inside a heat exchanger. When you open a hot tap, a flow sensor signals the control board, the elements energize, cold water flows across them and heats within 2 to 5 seconds, and self-modulating power adjusts the output to hold your set temperature. There is no storage tank and no standby heat loss.
What size electric tankless water heater do I need?
Size by your peak simultaneous demand and your coldest-month groundwater temperature. Add up the GPM of every fixture you might run at once, calculate the temperature rise from inlet to target output, then match the kW to that rise. A 2-shower household in a mixed climate usually needs 24 to 28kW. A 4-person home in a cold climate may need 36kW or more, which is at the limit of what residential electric can deliver.
Final Verdict: Which Electric Tankless Water Heater Should You Buy?
After three months of testing and cross-referencing plumber recommendations, the best electric tankless water heater for most homeowners in 2026 is the Rheem RTEX-18. It pairs 4.4 GPM with 99.8 percent efficiency, has the deepest review base of any unit in this roundup, and installs cleanly into a 200-amp panel without exotic electrical work.
If you need whole-house performance in a cold climate and have the panel capacity to support it, the Stiebel Eltron Tempra 29 Plus is the plumber’s pick and worth the premium. For point-of-use applications on a 120V circuit, the CAMPLUX 4.5kW is the only sensible answer. And if you want smart-home control and 8.7 GPM of flow, the WINTEMP 36kW WiFi is the only electric unit on the market that delivers both.
Whatever you pick, size to your coldest-month groundwater temperature, check your panel capacity before you buy, and plan to descale annually if you live in hard-water country. Done right, an electric tankless water heater will outlast a tank by a decade and pay you back in lower energy bills along the way.