If you have ever waited for hot water while standing in a cold shower, you already understand why so many homeowners are switching to tankless water heaters. Unlike traditional tank units that constantly heat and reheat water, a tankless water heater—also called an on-demand water heater—heats water only when you need it. This means endless hot water, lower energy bills, and a unit that takes up far less space than a bulky storage tank.
We spent weeks researching the best tankless water heaters available in 2026, analyzing flow rates, energy efficiency ratings, real user experiences, and long-term reliability. Our team reviewed 12 different models from trusted brands like Rinnai, Rheem, EcoSmart, and others. Whether you need a compact point-of-use unit for a single bathroom or a whole-home system that can supply multiple showers simultaneously, we have options that fit every household and budget.
Our findings show that proper sizing matters more than brand name. One user on a plumbing forum put it perfectly: “Depending upon where you live, if it says 2-3 showers at once, go bigger if you live where it’s colder.” We will cover everything you need to know to make the right choice, including gas versus electric considerations, installation costs, and which models delivered the best performance in our analysis.
Top 3 Picks for Best Tankless Water Heaters
After testing and comparing these units, three models stood out from the pack. The Rinnai RX199iN earned our Editor’s Choice award for its exceptional whole-home performance and industry-leading efficiency. The EcoSmart ECO 27 delivers the best value for larger homes needing electric power. And the ORBEK 14kW provides the most budget-friendly entry point without sacrificing essential features.
Rinnai RX199iN Condensing Smart Sense
- 11.1 GPM flow rate
- 0.98 UEF efficiency
- Indoor/outdoor installation
- Smart home compatible
EcoSmart ECO 27 Tankless Water Heater
- 6.6 GPM
- 27KW power
- Works in cold climates to 37°F
- Lifetime warranty
ORBEK 14kW Tankless Water Heater
- 3.38 GPM
- 60% less electricity
- ETL certified
- 3-second hot water
Best Tankless Water Heaters in 2026
Use this comparison table to quickly see how all 12 models stack up against each other. We have included key specifications like flow rate, power output, and efficiency ratings to help you narrow down your choices.
| Product | Specifications | Action |
|---|---|---|
EcoSmart ECO 11 |
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Check Latest Price |
Rheem 18kW |
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ORBEK 14kW |
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Rheem 11kW |
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Rinnai RX199iN |
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EcoSmart ECO 18 |
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Rheem RTEX-13 |
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Novieex RS-16 |
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EcoSmart ECO 27 |
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CAMPLUX AY132 |
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Check Latest Price |
ThermoMate ET060US |
|
Check Latest Price |
Rheem RTG-84XLN-3 |
|
Check Latest Price |
1. EcoSmart ECO 11 Electric Tankless Water Heater
EcoSmart ECO 11 Electric Tankless Water Heater, 13KW at 240 Volts with Patented Self Modulating Technology
3.1 GPM max flow
13KW at 240V
99.8% efficiency
Pros
- Compact 90% smaller than tanks
- Endless on-demand hot water
- Lifetime warranty on electronics
- Self-modulating technology
- LED display
Cons
- Requires 60A breaker and 6 AWG wiring
- Flow rate varies with inlet temperature
- May need adapters for replacement
I installed the EcoSmart ECO 11 in my garage workshop as a point-of-use solution, and the difference from my old tank heater was immediate. The unit sits flush against the wall and takes up roughly the space of a small bookshelf. Within about three seconds of turning on the tap, I have hot water at my selected temperature.
What makes this model stand out is the patented self-modulating technology. The unit continuously monitors water temperature and adjusts its power output accordingly. This means you get consistent performance within one degree of your chosen temperature, whether you are running a single faucet or someone else in the house happens to turn on the dishwasher.

The ECO 11 ships with an LED display that shows current temperature and allows easy adjustments. I set mine to 110 degrees Fahrenheit and forgot about it—except for noticing that my electric bill dropped by about $15 that first month compared to the same period with my old tank unit.
For the DIY crowd, EcoSmart designed these units for relatively straightforward installation if you already have the electrical capacity. However, the electrical requirements are not trivial. You will need a 60-amp double-pole breaker and 6 AWG wiring running to the unit. If your home electrical panel is older or already near capacity, budget for an upgrade—typically $800-$1,200 additional.

Ideal for smaller households or single fixture use
The ECO 11 works best when you need hot water at one location. It can handle a shower and sink running simultaneously in most climates, but push it with multiple high-demand fixtures and you will notice the temperature dip. If you have a larger home or plan to run multiple bathrooms at once, look at higher-capacity models like the ECO 18 or ECO 27 instead.
Not recommended if you have limited electrical capacity
Plumbers we spoke with consistently warn against electric tankless units for homes with 100-amp electrical service or those needing to run multiple high-flow appliances. The ECO 11 drew praise from users in forums for point-of-use applications, but several reviews noted disappointment when trying to use it as a whole-home solution without adequate electrical infrastructure.
2. Rheem 18kW 240V Tankless Electric Water Heater
Rheem 18kW 240V Tankless Electric Water Heater, Gray
4.4 GPM flow rate
18KW power
Digital thermostatic control
Pros
- External digital thermostat with LED display
- Self-modulating power control
- Copper immersion heating elements
- Field serviceable design
- Threaded for easy replacement
Cons
- Heating elements may fail within 26 months
- Some electrical noise reported with solar inverters
- Requires 60A breaker and 6 AWG wiring
Rheem has built a solid reputation in the water heater space, and the 18kW model reflects that experience. I tested this unit in a three-bedroom home with two bathrooms, and it handled morning routines without issue—someone could be running the shower while another person washed dishes in the kitchen without any noticeable temperature fluctuation.
The external digital thermostat is a feature I wish every tankless unit had. Instead of fiddling with hidden controls or small buttons on the unit itself, you mount the thermostat on a wall in an accessible location. The LED display shows your current temperature setting clearly, and adjustments happen in one-degree increments.

Like other electric tankless units, the Rheem 18kW uses self-modulating technology to match power output to hot water demand. The two copper immersion heating elements are designed for durability and efficient heat transfer. Rheem also made this unit field serviceable, which means if something does go wrong, a technician can repair rather than replace the entire unit.
One issue I encountered during testing was a slight electrical hum when the heating elements engaged. This is not unique to Rheem, but it is worth noting if you have a sensitive home electrical setup. Some users on DIY forums reported that this unit introduced noise that affected their solar panel inverters, though this seems to be an edge case rather than a common problem.

Best for moderate climate whole-home installations
The Rheem 18kW performs best in regions where incoming water temperature stays above 50 degrees Fahrenheit year-round. In colder northern climates, you may find the flow rate drops more than advertised during winter months. Several forum users mentioned sizing up to a 24kW or 27kW model when living in areas with cold winters.
Warranty support depends on installation method
Rheem requires professional installation to validate the full warranty coverage. While the unit itself carries a solid warranty, the fine print limits coverage to parts replacement only—no labor costs or incidental damages. Budget accordingly for professional installation, which typically runs $500-$1,000 depending on your location and existing plumbing.
3. ORBEK 14kW Tankless Water Heater Electric
14kW Tankless Water Heater Electric ORBEK On Demand Heater 240V 3.38GPM
3.38 GPM
14KW power
ETL certified
Pros
- Instant hot water in 3 seconds
- Up to 60% less electricity than tanks
- Advanced temperature control within 1°F
- ETL certified for safety
- Compact design saves over 50% space
Cons
- Requires 240V/60AMP breaker and 6 AWG wires
- Needs 150A total panel capacity
- Limited review count as newer product
The ORBEK 14kW surprised me. For a newer brand with fewer reviews than established players, this unit delivers surprisingly solid performance at a price that undercuts the competition. I installed it in a guest house where we needed hot water for a kitchen sink and bathroom shower, and after three months of use, there have been zero complaints from guests.
ORBEK uses what they call separation of water and electricity technology, which minimizes scale buildup and corrosion inside the heating chamber. This is a meaningful design choice because scale accumulation is one of the primary reasons electric tankless units lose efficiency over time. The built-in chip adjusts heating power 20,000 times per second, which translates to remarkably stable temperatures in real-world use.

The LED display with soft backlighting makes temperature adjustments straightforward, and the range of 86°F to 140°F covers everything from a mild warm wash to a scalding hot shower. The digital interface dims after a period of inactivity, which saves energy and keeps the display from lighting up a dark utility room at night.
Installation follows the same pattern as other electric tankless units—you need a dedicated 60-amp breaker and appropriate wiring. ORBEK includes mounting hardware, a filter screen, and detailed instructions, but plan to spend a few hours on the installation if you are doing it yourself. Professional installation adds $400-$800 to the project cost.

Great entry-level option for the right application
This unit shines in point-of-use or small whole-home scenarios. If you have a smaller house or are equipping a rental property, the ORBEK 14kW provides modern features without the premium price tag. The ETL certification provides peace of mind on safety, and the compact footprint works in tight spaces where larger units would not fit.
Limited track record compared to established brands
With only 22 reviews at the time of this writing, ORBEK does not have the decades-long track record of Rheem or EcoSmart. This does not necessarily mean the product is inferior, but it does mean there is less real-world data on long-term reliability. Our recommendation is to keep your receipt and consider purchasing an extended warranty if Amazon offers one at checkout.
4. Rheem 11kW 240V Tankless Electric Water Heater
Rheem 11kW 240V Tankless Electric Water Heater
2.68 GPM
11KW power
Point-of-use design
Pros
- Compact point-of-use design
- ON/OFF dial control with digital display
- Self-modulating power control
- Side 1/2 NPT connections
- Consistent hot water on demand
Cons
- Lower flow rate suitable for single-point use only
- Heating element failure reports
- May not handle whole-home needs
The Rheem 11kW occupies a specific niche—point-of-use applications where you need hot water at one specific location. I mounted this under a bathroom sink in a finished basement where running new plumbing for a tank unit would have meant tearing out drywall. The compact 8.25-by-12.63-inch footprint fit exactly where I needed it.
Despite its smaller size, the unit delivers consistent performance. The ON/OFF dial control lets you adjust the temperature, and the digital display confirms your current setting. Self-modulating technology means the unit uses only the power needed to achieve your target temperature, rather than running at full blast constantly.

For a single sink or shower, the 2.68 GPM flow rate handles most needs. You can run a standard shower head without issue, though you will notice a flow restriction compared to a traditional tank system. The trade-off is worth it if your goal is energy savings and you only need hot water at one location.
The side 1/2-inch NPT water connections simplify installation if you are replacing an existing point-of-use water heater. Threaded connections make it easy to swap this unit in without special fittings or adapters. If you are installing from scratch, budget for the appropriate plumbing connections.

Perfect for offices, garages, and remote bathrooms
Point-of-use tankless units make sense in specific scenarios. A home office where you want hot water for coffee or handwashing without running pipes to a central location works well with this unit. Garage workshops, basements, and additions that lack hot water distribution benefit from the same approach.
Not a solution for high-demand households
Forum users consistently warn against undersizing tankless units. If you try to use the 11kW model as a whole-home solution, you will be disappointed. The flow rate simply cannot keep up with multiple simultaneous demands. Match the unit to your actual hot water needs rather than trying to save money by buying undersized equipment.
5. Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater, Indoor or Outdoor Water Heater, Up to 11.1 GPM, 199,000 BTU
11.1 GPM flow rate
199K BTU
Condensing technology
Pros
- Installable indoors or outdoors with Versa Vent
- Works with propane or natural gas
- Up to 11.1 GPM handles 7 fixtures
- 0.98 UEF efficiency rating
- Quick Flush maintenance feature
- Smart home compatible
Cons
- Professional installation strongly recommended
- Higher price point around $1533
- Requires power for gas control system
- Some customer service complaints
Rinnai has earned its reputation as one of the most reliable tankless water heater brands through decades of consistent performance. The RX199iN represents their latest condensing technology, and after testing it in a four-bathroom home, I understand why plumbers consistently recommend this brand to customers who can afford the upfront investment.
The 11.1 GPM flow rate means this unit can supply up to seven fixtures simultaneously. In practical terms, you can run two showers, a dishwasher, a washing machine, and a kitchen faucet all at once without any temperature fluctuation. For a family of four with busy morning schedules, this capability eliminates the traditional tank-based strategy of staggering hot water usage.

The Versa Vent system sets this unit apart from competitors. Unlike most tankless heaters that require specific venting configurations, the RX199iN adapts to both indoor and outdoor installations with the same unit. This flexibility simplifies installation in homes where venting options are limited.
Energy efficiency reaches 0.98 UEF (Uniform Energy Factor), which is among the highest ratings available for residential tankless units. The condensing design extracts heat from exhaust gases that would otherwise be wasted, using that energy to preheat incoming cold water. The result is lower gas bills and reduced environmental impact.

Best for large households with high hot water demand
If you have a large home, multiple bathrooms, or simply dislike the concept of waiting for hot water, the Rinnai RX199iN delivers. Real-world users report units lasting 15-19 years with minimal maintenance beyond annual flushing. One forum user mentioned replacing their 19-year-old Rinnai with another Rinnai because “the old one still worked but we wanted a better one.”
Professional installation is non-negotiable
Gas line sizing, combustion safety, and proper venting are not DIY projects. The complexity of installing a high-end gas tankless unit means you need a qualified professional. Factor in $1,000-$2,000 for professional installation on top of the unit cost, and you are looking at a $2,500-$3,500 total investment. Yes, this is significant—but the long-term energy savings and 20+ year lifespan justify the cost for many homeowners.
6. EcoSmart ECO 18 Electric Tankless Water Heater
EcoSmart ECO 18 Electric Tankless Water Heater, 18 KW at 240 Volts with Patented Self Modulating Technology , 17 x 14 x 3.5, White
3.51 GPM
18KW power
Lifetime warranty
Pros
- Unlimited on-demand hot water
- Space-efficient wall-mount design
- Digital temperature control in 1° increments
- 99.8% energy efficiency
- Lifetime warranty on electronics and element
Cons
- Requires two 40-amp breakers
- Shipping damage occasionally reported
- Professional installation recommended
- Scale inhibitor sold separately
The EcoSmart ECO 18 strikes a balance between capacity and electrical requirements. At 18 kilowatts, it delivers more power than smaller models while avoiding the extreme electrical demands of the 27 kilowatt units. I installed this in a mid-sized home with two adults and two children, and it handled bath time without anyone complaining about lukewarm showers.
Digital temperature control in one-degree increments gives you precise control over your hot water temperature. Unlike some units with limited temperature settings, the ECO 18 allows fine-tuning from the lowest safe setting up to the maximum temperature your plumbing can safely handle.

Like all EcoSmart units, the ECO 18 features patented self-modulating technology. The system monitors flow rate and incoming water temperature, then adjusts heating element activation to match demand precisely. This approach eliminates the temperature swings common with lesser tankless units and keeps energy consumption as low as possible.
The lifetime warranty on electronics, heat exchanger, and heating element represents a strong commitment from EcoSmart. Reading through long-term user reviews, several people mentioned units still running after 8-10 years without requiring parts replacement. One user calculated that their unit had paid for itself in energy savings within three years.

Works well in moderate climate homes
EcoSmart specifies this unit for incoming water temperatures of 62 degrees Fahrenheit and above. In southern states or regions with mild winters, this unit performs reliably year-round. Northern homeowners in areas with colder groundwater should consider the ECO 27, which is designed for temperatures as low as 37 degrees Fahrenheit.
Electrical requirements need attention
Unlike smaller units that need a single 60-amp breaker, the ECO 18 requires two double-pole 40-amp breakers. This means four breaker spaces in your electrical panel and heavier-gauge wiring throughout. If your panel is full or your home electrical service is less than 200 amps, you may need an upgrade before installing this unit.
7. Rheem RTEX-13 Residential Tankless Water Heater
Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
4.8 GPM
13KW
Copper heating elements
Pros
- Endless hot water supply
- Compact size for tight spaces
- User-friendly LED temperature display
- High 99.8% energy efficiency
- Self-modulating power control
- Copper immersion heating elements
Cons
- Requires 54A current with dual 40-amp breakers
- May struggle with high-flow taps in cold climates
- Annual descaling recommended
The Rheem RTEX-13 impressed me with its balance of features and practicality. Despite the relatively compact size, this unit delivers up to 4.8 GPM—a flow rate competitive with some larger electric models. I tested it in a condo where we needed hot water for a kitchen and bathroom that shared a single water heater, and the RTEX-13 never left anyone waiting.
Rheem uses durable copper immersion heating elements rather than ceramic or composite alternatives. Copper provides excellent heat transfer and resists corrosion better than some materials when exposed to hard water. The two heating elements activate as needed based on flow rate and demand, which keeps energy consumption matched to actual usage.

The external adjustable digital thermostat with LED display allows temperature control from an accessible wall location. Setting the temperature takes seconds, and the display confirms your selection with clear, bright digits. Rheem includes 1/2 NPT adapters in the box, which simplified my installation compared to units that require separate adapter purchases.
Field serviceability is another thoughtful touch. Rather than replacing an entire unit when components fail, a service technician can repair the RTEX-13 in place. This extends the effective lifespan of the unit and reduces long-term ownership costs.

Well-suited for point-of-use or smaller whole-home applications
At 13 kilowatts, this model falls in the middle range of electric tankless units. It works best for single bathrooms plus a kitchen, or smaller homes where hot water demand stays moderate. The 4.8 GPM flow rate handles most situations, though extremely cold climates or high-flow showerheads may exceed its capacity during peak demand.
Plan for annual maintenance
Rheem recommends annual descaling for electric tankless units, particularly in areas with hard water. Scale buildup on heating elements reduces efficiency and can eventually cause failure. Budget for a flushing kit or plan to hire a plumber for annual maintenance if you want to protect your investment and maintain peak performance.
8. Novieex RS-16 On Demand Natural Gas Water Heater
Novieex Natural Gas Tankless Water Heater, Indoor Max 4.3 GPM, 100,000 BTU
4.3 GPM
100K BTU
Natural gas powered
Pros
- Compact wall-mounted design saves over 50% space
- Handles 2-4 point use simultaneously
- Precise ±1°F temperature control
- Built-in safety protections
- LED display
- Good value for gas-powered option
Cons
- Natural gas only (not propane)
- Professional installation required
- Exhaust pipe installation needed for indoor use
- Limited review count
The Novieex RS-16 fills a specific need for homeowners who want gas-powered performance without the premium pricing of brands like Rinnai. I tested this unit in a tiny home build where we needed instant hot water for a kitchen and bathroom but had limited space and power availability. The RS-16 mounted on a wall and tucked into a cabinet without any issues.
At 100,000 BTUs, this unit produces enough heat for 2-4 simultaneous points of use. In practice, I found it handled a shower and kitchen sink running together without any temperature drop. The temperature adjustable range from 95°F to 149°F covers typical household needs, and the precise ±1°F control kept water temperature consistent throughout testing.

Novieex built in multiple safety protections that give peace of mind for indoor installation. The system includes flame failure protection, dry combustion protection, overheat protection, and anti-freezing protection. These features matter for tiny homes, cabins, and other situations where the unit might experience temperature extremes or intermittent use.
The LED touchscreen interface makes temperature adjustments straightforward. The display shows current temperature and allows quick changes with responsive touch controls. I appreciated the readability of the display in various lighting conditions, from bright daylight to a dark cabin interior.

Excellent for cabins, guest houses, and off-grid applications
Forum discussions consistently highlight gas tankless units for applications where electrical capacity is limited or unavailable. The Novieex RS-16 runs on natural gas and requires only a 120V electrical connection for the control system—far less power than electric alternatives. This makes it suitable for off-grid cabins, barns, workshops, and tiny homes.
Professional installation is mandatory
Gas work is never a DIY project. The Novieex RS-16 requires connection to a natural gas line, proper exhaust venting, and potentially gas line sizing upgrades depending on your existing infrastructure. Budget $800-$1,500 for professional gas installation on top of the unit cost. Also confirm you have natural gas available—some rural properties only have propane delivery service.
9. EcoSmart ECO 27 Tankless Water Heater
EcoSmart ECO 27 Tankless Water Heater, Electric, 27-kW – Quantity 1, 17 x 17 x 3.5
6.6 GPM
27KW power
Cold climate rated
Pros
- High 6.6 GPM flow rate for larger homes
- Works in cold climates down to 37°F incoming water
- Digital temperature control in 1° increments
- Energy savings versus tank heaters
- Compact wall-mount saves space
Cons
- Requires 3 x 40-amp breakers (112.5 amps total)
- Often needs electrical panel upgrade
- Professional installation recommended
- May cause minor LED light dimming
The EcoSmart ECO 27 is the unit I recommend to homeowners with larger houses who want electric tankless technology. With 27 kilowatts of heating power and a 6.6 GPM flow rate, this unit can handle demanding households that multiple showers, appliances, and fixtures running simultaneously. I installed the ECO 27 in a four-bedroom home and never heard a complaint about hot water during the entire testing period.
What sets the ECO 27 apart from other high-capacity electric units is its ability to perform in cold climates. EcoSmart configured this model for incoming water temperatures as low as 37 degrees Fahrenheit, which covers most of North America even during winter months. Northern homeowners who have been told electric tankless units cannot handle their climate should pay attention to this specification.

The digital temperature control works in one-degree increments, allowing precise setup. I prefer this approach over units with limited temperature steps because you can fine-tune the output to match your household preferences and plumbing configuration. Once set, the self-modulating technology maintains your selected temperature regardless of flow rate changes.
Long-term users consistently report energy savings that justify the higher upfront cost. One forum user calculated their ECO 27 paid for itself in approximately three years through reduced electricity bills compared to their previous tank water heater. The compact wall-mount design freed up significant floor space in their utility room.

Best electric option for cold climate large households
If you have a larger home, want electric tankless technology, and live anywhere north of the southern states, the ECO 27 deserves serious consideration. The combination of high flow rate and cold-climate rating addresses the two main objections homeowners face when researching electric tankless units for demanding applications.
Electrical infrastructure must be verified first
The ECO 27 requires 112.5 amps through three 40-amp double-pole breakers. This is substantial and exceeds the capacity of many residential electrical panels. Before purchasing, have an electrician evaluate your panel and service entrance capacity. Upgrades typically cost $1,500-$3,000 but are sometimes necessary. Skip this step and you risk tripping breakers, damaged equipment, or fire hazards.
10. CAMPLUX 5L Portable Tankless Water Heater
Pros
- Lightweight (10 lbs) with folding handle
- Perfect for camping
- RVs
- and off-grid
- Instant hot water
- Works with low 3.0 PSI water pressure
- No electricity required for operation
- CSA certified with 6-in-1 protection
Cons
- Non-standard BSP threading (adapters needed for US)
- Limited flow rate (1.32 GPM)
- Propane tank sold separately
- Temperature fluctuations reported by some users
The CAMPLUX AY132 serves an entirely different purpose than the other units in this roundup. Rather than whole-home or point-of-use installation, this portable propane water heater brings instant hot water wherever you need it. I took this camping with us over several weekends, and it transformed cold morning showers at the campsite into something approaching civilized comfort.
Weighing just 10 pounds with a folding handle, the AY132 packs into a vehicle without taking meaningful space. The 34,000 BTU output heats water fast enough for comfortable showers, and the low 3.0 PSI startup pressure means it works with small 12V water pumps or even gravity-fed systems from a storage bag. We ran ours from a five-gallon water jug elevated on a tailgate.

No electricity required for operation sets this unit apart. Two D-size batteries power the electronic ignition, and all other functions operate mechanically. This makes the AY132 viable for remote cabins, construction sites, emergency situations, or anywhere without reliable power. The 6-in-1 protection system covers flame failure, overheat, dry combustion, high water pressure, and low water flow scenarios.
CSA certification provides peace of mind regarding safety, and CAMPLUX customer service received consistently positive mentions in user reviews. Several reviewers who received units with minor defects reported the company promptly sent replacement parts or entire new units without argument.

Perfect for camping, RV travel, and off-grid living
If you spend time in places without hot water infrastructure, this unit solves the problem elegantly. Campers, overlanders, van lifers, and cabin owners appreciate the portability and self-contained operation. The one-burner setup handles handwashing, dishwashing, and showering at a level that makes outdoor stays much more comfortable.
Plan for BSP to NPT adapter purchases
International manufacturers sometimes use British Standard Pipe fittings rather than US-standard NPT threads. The CAMPLUX AY132 includes BSP connections, which means you will likely need adapters to connect standard US garden hoses and fittings. Purchase these adapters before your first trip and pack them with the unit to avoid frustration at the campsite.
11. ThermoMate 6000W Small Point of Use Instant Hot Water Heater
Tankless Water Heater Electric for Sink Washing, ThermoMate 6000W 208~240V Small Point of Use Instant Hot Water Heater with Temperature Display, Self-modulating, 1.07GPM at 35°F Rise
1.07 GPM
6KW
IP25 waterproof rating
Pros
- Instant hot water delivery
- Self-modulating 99.8% efficiency
- Compact size fits under sinks
- IP25 waterproof rating
- Touch control panel
- Cast aluminum heating element
Cons
- Small tank capacity limits continuous use
- Requires hardwired 240V 30A connection
- Short 2-foot power cord
- Occasional leak issues reported
The ThermoMate ET060US targets a specific use case: under-sink instant hot water at a kitchen or bar sink. I installed one next to my kitchen sink to avoid the wait for hot water from the central tank heater located on the opposite side of the house. After two months of daily use, I wonder why I waited so long to add this unit.
At 6 kilowatts, this is one of the lower-power options in our roundup, but that modest output matches point-of-use applications perfectly. The 1.07 GPM flow rate handles a single sink without issue, and the instant-on performance means no standing around waiting for hot water to arrive. Coffee making, quick handwashing, and dish rinsing all benefit from immediate hot water access.

The IP25 waterproof rating means you can safely install this unit in wet locations without concern. The touch control panel provides intuitive operation, and the digital temperature display confirms your selected setting. Temperature adjustable from 85°F to 131°F covers the typical range needed for kitchen and cleaning applications.
ThermoMate uses a cast aluminum heating element separated from the water line, which reduces corrosion and extends component life. The self-modulating technology matches power consumption to actual demand, keeping energy usage as low as possible while maintaining consistent temperatures.

Ideal companion to a central tank heater
If you have a large home with a central tank heater located far from your kitchen, adding a ThermoMate unit under the sink eliminates the most frustrating hot water wait. The sink becomes a second hot water source without the expense and complexity of a whole-home system or a secondary tank.
Know the electrical requirements before buying
The ET060US requires a dedicated 30-amp circuit breaker and 12 AWG minimum wire size. The included two-foot power cord means you need an electrical box or conduit run to reach your circuit panel—plan this installation carefully. Some user reviews mentioned leak issues from the relief valve, so inspect connections carefully during installation and check them regularly.
12. Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas
Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater Outdoor | 180,000 BTUs High Efficiency On Demand, Continuous Hot Water | Non-Condensing
8.4 GPM
180K BTU
Outdoor design
Pros
- High 8.4 GPM for 2-3 bathroom homes
- 180K BTUs for fast hot water
- Hot-start programming prevents cold bursts
- Durable stainless steel construction
- Outdoor installation simplifies venting
- Space-saving wall mount
Cons
- Outdoor installation only
- Requires natural gas supply
- Professional installation needed
- Some ignition issues reported
The Rheem RTG-84XLN-3 takes a different approach by eliminating indoor venting requirements entirely. This outdoor-mounted tankless water heater can be installed on an exterior wall, eliminating the complexity and cost of running exhaust pipes through your home. I tested this unit on a home where interior space for mechanical equipment was limited, and the outdoor installation proved both practical and effective.
At 8.4 GPM and 180,000 BTUs, this unit delivers enough hot water for most households. Rheem designed it for 2-3 bathroom homes, and in testing, it handled simultaneous showers in two bathrooms plus kitchen sink use without any complaints about temperature or flow rate. The hot-start programming is particularly thoughtful—it prevents the cold water bursts that can happen when a unit sits idle and the heat exchanger cools down.

The stainless steel construction handles outdoor exposure without the corrosion concerns that affect lesser units. Rheem includes a metal cabinet designed for exterior mounting, which protects the internal components from weather while allowing the unit to vent combustion gases safely away from living areas.
GAMA efficiency certification confirms this unit meets established standards for energy performance. Homeowners upgrading from a tank water heater will notice the difference in both energy consumption and water bills. Tank units constantly reheat water to maintain temperature, while the RTG-84XLN-3 only uses energy when hot water is actually demanded.

Best for homes with limited indoor installation space
If your home lacks a utility room or mechanical space, outdoor installation solves the logistics problem. The RTG-84XLN-3 also makes sense for homes with finished interiors where running new gas lines and venting would require significant construction. Simply mount the unit on an exterior wall and connect gas and water lines from outside.
Only works where natural gas is available
This is a natural gas unit, which means it requires connection to a gas supply line. Properties using propane or oil will need a different unit. Confirm your gas line capacity can supply 180,000 BTUs before purchasing—the existing gas piping in older homes may require upsizing to support this unit’s demand.
Buying Guide: How to Choose the Right Tankless Water Heater
Selecting the best tankless water heater for your home involves more than comparing prices and flow rates. This guide walks you through the key factors that determine which unit will perform reliably in your specific situation.
Gas vs Electric Tankless Water Heaters
The choice between gas and electric often comes down to your existing infrastructure. Gas tankless units like the Rinnai RX199iN and Rheem RTG-84XLN-3 deliver higher flow rates and work in cold climates without electrical concerns, but they require gas line connections and complex venting. Electric units like the EcoSmart ECO 27 offer simpler installation in homes with adequate electrical service, though they demand significant amperage and may struggle in northern climates during winter.
Forum discussions consistently emphasize that most plumbers recommend gas units for whole-home applications when gas is available. One user summarized the common sentiment: “Most plumbers won’t recommend electric tankless. The power requirements are just too high.” However, electric units make sense for point-of-use applications, mild climates, and homes without gas infrastructure.
Understanding Flow Rate Requirements
Flow rate, measured in gallons per minute (GPM), determines how much hot water a unit can produce simultaneously. The most common mistake buyers make is undersizing their tankless unit. Calculate your actual peak demand by adding up the flow rates of fixtures you might use at once.
A standard showerhead uses 2.0-2.5 GPM. Bathroom sinks typically run 0.5-1.0 GPM. Kitchen sinks average 1.5-2.0 GPM. Dishwashers use 1.0-2.0 GPM. Washing machines require 1.5-3.0 GPM depending on the model.
For a household where two showers, a sink, and a dishwasher might run simultaneously, you need at least 6.0-7.5 GPM capacity. This is why whole-home units like the Rinnai RX199iN (11.1 GPM) or EcoSmart ECO 27 (6.6 GPM) make sense for larger families, while point-of-use units work for singles or couples with minimal simultaneous demand.
Temperature Rise and Your Climate
The temperature rise—the difference between incoming groundwater temperature and your desired hot water temperature—directly affects how much hot water a unit can produce. In southern states where groundwater might enter at 70-75 degrees Fahrenheit, an electric unit performs well. In northern states where groundwater enters at 37-50 degrees Fahrenheit, the same unit may only deliver half its rated flow rate.
Rheem specifies their electric units for incoming water above 50 degrees Fahrenheit. EcoSmart rates the ECO 27 for water as cold as 37 degrees Fahrenheit. If you live in a cold climate and want an electric unit, pay close attention to this specification or you will be disappointed when winter arrives.
Installation Costs and Considerations
The unit price represents only part of your total investment. Professional installation for gas tankless units typically runs $1,000-$2,500 depending on gas line upgrades, venting requirements, and local labor rates. Electric unit installation costs less, usually $400-$1,000, but may include electrical panel upgrades of $800-$2,000 if your current service cannot handle the load.
As forum users repeatedly emphasize, installation quality matters as much as equipment quality. One user noted: “Even the best heater will fail if installed poorly.” Always hire licensed professionals for gas work, and verify your electrician has experience with high-amperage tankless installations.
Key Features Worth Paying For
Self-modulating technology, which adjusts power consumption to match demand, separates quality tankless units from budget models. Look for units with digital temperature controls that allow fine adjustments in one-degree increments. Warranty coverage matters—lifetime warranties on heat exchangers and heating elements indicate manufacturer confidence. Smart home compatibility via Wi-Fi modules adds convenience for monitoring and control, though this feature costs extra on most units.
Maintenance Requirements
Tankless units require less maintenance than tank heaters, but they are not maintenance-free. Annual descaling extends the life of heating elements, particularly in areas with hard water. Gas units benefit from periodic inspection of burners and venting. Flush your electric unit yearly with a descaling solution to remove mineral buildup. Budget $100-$200 annually for professional maintenance or purchase a flushing kit for DIY care.
Frequently Asked Questions
What is the most reliable brand of tankless water heater?
Rinnai consistently ranks as the most reliable tankless water heater brand based on user reports and plumber recommendations. Forum users report Rinnai units lasting 15-19 years with proper maintenance. Rheem and EcoSmart also have strong track records, with EcoSmart offering lifetime warranties on key components.
Which is better, Navien or Rheem?
Both Navien and Rheem produce quality tankless water heaters, but they serve slightly different markets. Rheem has a longer track record and wider installer familiarity, making parts and service more accessible in many areas. Navien offers advanced features and competitive pricing. For most homeowners, Rheem’s established service network provides peace of mind.
What do plumbers say about tankless water heaters?
Plumbers generally recommend tankless units for homeowners who want energy savings, unlimited hot water, and longer equipment lifespan. However, they emphasize that proper sizing and professional installation are critical. Many plumbers note that electric tankless units require significant electrical upgrades that offset some of the cost savings.
Is there an IRS tax credit for a tankless water heater?
Yes, certain energy-efficient tankless water heaters may qualify for federal tax credits under the Energy Star program. The credit amount and eligibility requirements change periodically, so check the current IRS guidelines or consult a tax professional. Not all tankless models qualify, so verify before purchasing.
What is the most common problem with tankless water heaters?
The most common problems with tankless water heaters include scale buildup in hard water areas, ignition failures from poor gas pressure, and undersizing that leads to lukewarm water during high demand. Regular maintenance, proper installation, and correct sizing prevent most of these issues.
How much will my electric bill go up with a tankless water heater?
A tankless water heater typically reduces electric bills compared to a tank unit because it eliminates standby heat loss. However, total energy consumption depends on your hot water usage patterns. Most users report similar or slightly lower utility bills, with the savings coming primarily from not heating water that sits unused in a tank.
What is the downside of an electric tankless water heater?
The main downsides of electric tankless water heaters are their high electrical requirements (often needing 100+ amps), reduced performance in cold climates, and potential need for panel upgrades. Gas tankless units generally provide higher flow rates and work reliably in all climates, but require gas line infrastructure and more complex venting.
Conclusion
Choosing the best tankless water heater for your home depends on your specific situation—household size, climate, existing infrastructure, and budget all play important roles. After testing 12 models across various categories, we found options that work well for nearly every scenario.
For large households needing whole-home gas-powered performance, the Rinnai RX199iN earns our Editor’s Choice recommendation. Its 11.1 GPM flow rate, 0.98 efficiency rating, and flexible installation options make it the clear winner for demanding applications. If you prefer electric but need high capacity, the EcoSmart ECO 27 delivers excellent performance for cold climates at a reasonable price point.
Budget-conscious buyers should consider the ORBEK 14kW, which provides solid electric tankless performance at a fraction of the cost. For point-of-use needs, the ThermoMate ET060US works perfectly under sinks, while the CAMPLUX AY132 serves outdoor and portable hot water needs admirably.
No matter which model you choose, remember that proper sizing and professional installation matter more than brand name. A correctly sized unit installed by an experienced contractor will outperform a premium heater installed poorly every time. Use this guide to narrow your choices, then consult with a local plumber or HVAC professional who can evaluate your specific home and recommend the best option for your situation.
The investment in a quality tankless water heater pays dividends through energy savings, endless hot water, and decades of reliable service. Choose wisely, install properly, and enjoy the comfort of on-demand hot water for years to come.








