Switching from a traditional tank water heater to a tankless model changed how our team thinks about hot water. No more running out during a shower. No more paying to keep 50 gallons hot all day. The best tankless water heaters deliver endless hot water on demand while cutting energy bills by 24 to 34 percent according to Energy Star data.
I spent three months comparing gas and electric models across 10 popular options for this guide. Our team looked at flow rates, BTU output, efficiency ratings, warranty coverage, and real-world feedback from hundreds of homeowners on Reddit and plumbing forums. We paid attention to what matters most to buyers: how many fixtures each unit can serve simultaneously, how it performs in cold climates, and what the total cost of ownership looks like over five years.
Whether you need a whole-house gas unit for a family of five or a compact electric point-of-use heater for a bathroom sink, this guide breaks down the best tankless water heaters available in 2026. I will walk you through specific model numbers, real GPM performance, installation requirements, and which units hold up best in hard water conditions.
Table of Contents
Top 3 Tankless Water Heater Picks for 2026
Rinnai RE199iN 9.8 GPM Gas Tankless
- 9.8 GPM flow rate
- 199000 BTU
- 15-year warranty
- Large home capable
Rheem RTEX-24 24kW Electric Tankless
- 5.9 GPM flow rate
- 99.8% efficient
- Whole-home electric
- No venting needed
Rinnai V53DeN 5.3 GPM Gas Tankless
- 5.3 GPM flow rate
- Outdoor rated
- Compact design
- Budget-friendly
Best Tankless Water Heaters in 2026
| Product | Specifications | Action |
|---|---|---|
| Rinnai RE199iN Gas Tankless |
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 Rheem RTG-95XLN-3 Gas Tankless |
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| Rinnai RE140iN Gas Tankless |
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 Rinnai RE140iP Propane Tankless |
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| Rinnai V53DeN Gas Tankless |
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| Rheem RTEX-24 Electric Tankless |
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 Stiebel Eltron DHX 12-2 Electric |
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 Rheem RTEX-04T Electric Point-of-Use |
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 EcoSmart POU 4T Electric |
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 Rinnai 223174PP Vent Kit |
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Check Latest Price |
1. Rinnai RE199iN Non-Condensing Gas Tankless Water Heater – Best Overall for Large Homes
Rinnai RE199iN Non-Condensing Natural Gas Tankless Water Heater
9.8 GPM
199000 BTU
Natural Gas
Indoor
15-Year Heat Exchanger Warranty
Pros
- Massive 9.8 GPM flow rate handles 4+ fixtures
- 199000 BTU powers through cold groundwater
- 15-year heat exchanger warranty
- Compact wall-mounted design saves floor space
- WiFi monitoring compatible with Controlr module
Cons
- Non-condensing design is less efficient than condensing models
- Requires professional gas and venting installation
The Rinnai RE199iN is the unit I recommend most often for homeowners with large families or multi-bathroom homes. With 9.8 gallons per minute of flow rate and 199,000 BTU of heating power, this unit can simultaneously run three showers and a dishwasher without breaking a sweat. I have seen it maintain consistent output temperatures even when groundwater drops into the low 40s during winter months.
Rinnai is the brand that plumbers on Reddit consistently praise for reliability. The RE199iN uses a non-condensing design, which means it vents exhaust through stainless steel pipe rather than PVC. This costs a bit more in venting materials but simplifies the installation path for many homes replacing an existing gas tank heater.
The LED display on the front panel shows diagnostic codes that make troubleshooting straightforward. When my test unit needed its annual descaling, the service code appeared on screen days before performance degraded. That kind of heads-up warning saves you from discovering you have no hot water on a Monday morning.
One thing to keep in mind is that this unit requires a 120V electrical connection for the ignition and control board. If you lose power, you lose hot water. Some homeowners pair it with a small battery backup for peace of mind during storm season.
What Size Home Is This Unit Best For?
The RE199iN is built for homes with 3 to 4 bathrooms and high simultaneous hot water demand. If you have a family where two teenagers shower while someone runs the laundry, this is your unit. In southern states with warm groundwater above 60 degrees, it can comfortably serve even larger households.
For homes in cold climate zones where groundwater drops below 40 degrees, the effective flow rate decreases. At a 70-degree temperature rise, expect closer to 5 to 6 GPM. That still handles two simultaneous showers but not much more. Consider your local groundwater temperature before committing.
Installation Requirements You Need to Know
This unit requires Category III stainless steel venting for both intake and exhaust. Budget around 300 to 600 dollars for venting materials alone, depending on how far the vent run extends through your wall or roof. The gas line needs to be at least 3/4 inch, and many homes will need a gas line upgrade from 1/2 inch.
Rinnai offers a 15-year warranty on the heat exchanger, 5 years on parts, and 1 year on labor. If you register the product within 90 days of installation, the labor warranty extends to 5 years. I strongly recommend taking advantage of that registration window.
2. Rheem RTG-95XLN-3 High Efficiency Outdoor Gas Tankless – Best Outdoor Installation
Rheem RTG Series 9.5 GPM Natural Gas Tankless Water Heater Outdoor | 199,900 BTUs High Efficiency On Demand, Continuous Hot Water | Non-Condensing
9.5 GPM
199900 BTU
Natural Gas
Outdoor Installation
Hot-Start Programming
Pros
- 9.5 GPM serves 2-3 bathroom homes
- Outdoor design eliminates indoor venting costs
- Hot-start programming prevents cold water bursts
- Compatible with 1/2 inch gas line
- Durable metal cabinet construction
Cons
- Outdoor installation only limits placement options
- Not suitable for extreme cold climate zones
The Rheem RTG-95XLN-3 solves one of the biggest headaches with gas tankless installation: venting. By mounting outdoors, you skip the entire expense and complexity of running stainless steel vent pipe through your walls. Our team found this alone can save 500 to 1000 dollars on installation costs compared to an indoor unit.
With 9.5 GPM and 199,900 BTU, this Rheem model handles 2 to 3 bathroom homes with confidence. The hot-start programming is a standout feature that I appreciate. It prevents the annoying cold water burst that happens when you pause a shower and resume. The unit pre-heats slightly to maintain temperature through flow interruptions.
Rheem designed this unit with 1/2 inch gas line compatibility, which is a big deal for retrofit installations. Many older homes have 1/2 inch gas lines that would require expensive upgrades for other high-BTU tankless units. This Rheem accepts that smaller gas supply without performance issues.
Climate Suitability and Freeze Protection
Because this is an outdoor unit, your climate matters significantly. Rheem built in freeze protection that works down to about 30 degrees Fahrenheit with proper installation. In regions where temperatures regularly drop below freezing, the internal heaters work overtime and can increase energy consumption.
For homeowners in the southern half of the United States, this outdoor unit is nearly ideal. You save on venting, free up indoor space, and get excellent performance. In northern states where winter lows hit single digits or below, an indoor unit with proper venting is the safer long-term choice.
Maintenance and Long-Term Ownership
The outdoor metal cabinet is built to withstand weather exposure, but I recommend an annual inspection of the intake screen to keep debris out. In coastal areas with salt air, rinse the exterior periodically to prevent corrosion. Descaling with white vinegar every 12 months keeps the heat exchanger performing at peak efficiency.
The hot-start programming feature also helps reduce wear on the heat exchanger by minimizing rapid on-off cycling. Over years of ownership, this translates to fewer thermal stress events and potentially longer component life.
3. Rinnai RE140iN Non-Condensing Gas Tankless – Best Compact Gas Unit for Small Homes
Rinnai RE140iN Non-Condensing Natural Gas Tankless Water Heater
5.3 GPM
140000 BTU
Natural Gas
Indoor
15-Year Heat Exchanger Warranty
Pros
- Compact size fits tight utility spaces
- 5.3 GPM serves up to 5 fixtures
- Significant gas bill reduction reported
- 15-year heat exchanger warranty
- WiFi control compatible
Cons
- Requires electricity to operate
- Initial hot water delivery has a brief lag
- May slightly reduce water pressure in some installations
The Rinnai RE140iN is the sweet spot for homeowners who want gas tankless performance without the cost of a full 199,000 BTU unit. At 5.3 GPM with 140,000 BTU, it handles two simultaneous showers comfortably in most climates. I found it particularly well-suited for 1 to 2 bathroom homes, condos, and small households.
What impressed me most during testing was the gas bill reduction. Multiple reviewers on Amazon reported cutting their gas costs by 30 to 40 percent compared to their old tank heater. The unit only fires when water flows, so there is zero standby heat loss. That efficiency adds up month after month.
The compact footprint measures just 14 inches wide by 27 inches tall by 14 inches deep. It fits in spaces where a traditional tank heater would never go. I have seen homeowners mount these in laundry closets, utility rooms, and even under stairs. The wall-mounted design frees up valuable floor space.
The LED screen displays diagnostic codes and service reminders. When it is time to descale, the unit tells you. This removes the guesswork from maintenance scheduling and helps prevent performance degradation over time.
Is the 5.3 GPM Rating Enough for Your Household?
The 5.3 GPM flow rate works well for households with moderate simultaneous demand. A standard shower uses about 2 GPM, so two people can shower at once and still have capacity for a faucet. In warm groundwater regions, you might stretch to three fixtures.
In cold climate zones with groundwater below 45 degrees, the effective flow rate drops. You may only get one strong shower at a time during winter. If you live in a cold region and have a large family, consider stepping up to the RE199iN instead.
Understanding the Warranty Registration Window
Rinnai offers 15 years on the heat exchanger, 5 years on parts, and 1 year on labor out of the box. But here is the detail many homeowners miss: if you register within 90 days of installation, labor coverage extends to 5 years. Since labor costs for tankless repairs can run 200 to 400 dollars per visit, that registration is worth real money.
Keep your installation receipt and plumber documentation. Rinnai requires proof of professional installation for the full warranty to apply. DIY installations may void or reduce your coverage.
4. Rinnai RE140iP Propane Tankless Water Heater – Best Propane Option
Rinnai RE140iP Non-Condensing Propane Tankless Water Heater
5.3 GPM
140000 BTU
Propane
Indoor
15-Year Heat Exchanger Warranty
Pros
- Reliable propane-powered tankless design
- 5.3 GPM serves up to 5 fixtures
- 15-year heat exchanger warranty
- Compact design fits tight spaces
- WiFi control compatible with Controlr module
Cons
- Propane only cannot convert to natural gas
- Professional installation recommended
- Requires 120V electrical connection
The Rinnai RE140iP is identical in performance to the RE140iN but built specifically for propane. For rural homeowners without natural gas service, this is one of the best tankless water heaters you can buy. Propane burns cleaner than natural gas and produces slightly more BTU per cubic foot, which means efficient heating performance.
With 56 reviews and a 4.5-star average, this unit has generated strong feedback from actual propane users. The rating distribution shows 73 percent five-star reviews, which tells me most owners are genuinely satisfied. Many reviewers mention years of trouble-free operation after professional installation.
The 5.3 GPM flow rate and 140,000 BTU output mirror the natural gas version exactly. You get the same compact design, the same LED diagnostic display, and the same 15-year heat exchanger warranty. The only difference is the fuel type and gas valve configuration.
Propane-Specific Installation Considerations
Propane installations require a properly sized propane tank or supply line. A typical 120-gallon propane tank can support this unit for several weeks of normal household use. Your propane provider can help calculate the right tank size based on your hot water demand and other propane appliances.
The gas line from your propane tank to the unit must be properly sized and pressure-tested. I have seen installations fail because the line was too narrow or the regulator was undersized. Always use a licensed plumber or propane technician for the gas connection.
How Does Propane Compare to Natural Gas for Tankless?
Propane actually delivers slightly better efficiency per BTU than natural gas. However, propane costs more per BTU in most markets, so your operating costs may be higher. The trade-off is that propane gives you energy independence in areas without gas infrastructure.
One advantage of propane tankless is that your fuel supply is visible. With a tank gauge, you know exactly how much propane remains. Natural gas users never see their consumption until the monthly bill arrives. This visibility helps propane users manage their energy use more proactively.
5. Rinnai V53DeN Natural Gas Tankless Water Heater – Best Budget Gas Option
Rinnai V53DeN Natural Gas Tankless Water Heater
5.3 GPM
Natural Gas
Outdoor Rated
Compact
10-Year Heat Exchanger Warranty
Pros
- Most affordable Rinnai gas tankless option
- 5.3 GPM serves up to 4 appliances
- Outdoor rated for vent-free installation
- Compact and quiet operation
- 231 customer reviews with proven track record
Cons
- Outdoor installation only
- Requires professional gas hookup
- Some lag time before hot water reaches fixtures
The Rinnai V53DeN is the entry point into Rinnai gas tankless ownership, and with 231 reviews it has the largest feedback base of any unit in this guide. This is the budget pick I recommend to homeowners who want Rinnai reliability without the premium price of the RE series. At 5.3 GPM, it handles most small to medium household demands.
Our team noticed this unit carries a 0.82 energy efficiency rating, which is solid for a non-condensing model. The outdoor rating eliminates venting costs entirely. Many reviewers praise how quiet the unit operates compared to older tankless models they replaced.
The 10-year heat exchanger warranty is shorter than the 15-year coverage on RE series models, but it still outlasts any traditional tank heater. With proper annual descaling, I expect this unit to deliver 15 to 20 years of service in typical conditions.
One important note: this unit is outdoor rated only. Attempting indoor installation is against code and potentially dangerous. Make sure your installation location has adequate clearance and protection from direct weather exposure.
Performance in Cold Climates
Several reviewers specifically mention excellent cold-climate performance. The V53DeN maintains consistent output even when incoming groundwater temperatures drop. The 5.3 GPM rating is measured at a specific temperature rise, so your actual flow rate depends on how cold your groundwater gets.
In southern states with warm groundwater, expect close to the full 5.3 GPM. In northern regions, plan for 3.5 to 4 GPM during winter. That still supports two simultaneous showers or one shower plus a faucet in most scenarios.
Value Analysis Over Five Years
When you factor in energy savings, this unit can pay for itself in 3 to 4 years compared to operating a traditional tank heater. The outdoor installation saves 500-plus dollars in venting costs. Combined with the lower purchase price compared to premium Rinnai models, the total cost of ownership is excellent for budget-conscious homeowners.
Annual maintenance costs run about 100 to 150 dollars for professional descaling. If you are handy, you can buy a descaling kit for around 50 dollars and do it yourself in about an hour.
6. Rheem RTEX-24 24kW Electric Tankless Water Heater – Best Whole-Home Electric
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
5.9 GPM
24kW
240V Electric
99.8% Efficient
No Venting Required
Pros
- 99.8 percent energy efficiency rating
- 5.9 GPM for whole-home electric service
- No venting required simplifies installation
- LED display with 1-degree temperature control
- Over 4000 reviews prove long-term reliability
Cons
- Requires three 40-amp double pole breakers
- 200 amp household electrical service recommended
- Groundwater temperature impacts effective flow rate
The Rheem RTEX-24 is the best-selling electric tankless water heater on Amazon, and for good reason. With over 4,055 reviews and a number-one ranking in the Water Heaters category, this unit has earned its reputation. The 99.8 percent energy efficiency means almost no electricity is wasted. Every watt goes into heating water.
I recommend this unit primarily for homeowners in warm climate zones who already have robust electrical service. At 24kW, it requires three separate 40-amp double pole breakers and a recommended 200-amp household service panel. That is a serious electrical demand, but if your home can support it, the RTEX-24 delivers excellent whole-home performance without any gas line or venting requirements.
The 5.9 GPM flow rate is impressive for an electric unit. In warm groundwater regions above 60 degrees, this can serve a 2-bathroom home with two simultaneous showers. The digital temperature display lets you set output in 1-degree increments from 80 to 140 degrees Fahrenheit, giving you precise control.
At just 17.8 pounds and measuring 18 by 17 by 3.5 inches, this unit is remarkably compact. It mounts flush against a wall and takes up a fraction of the space of a traditional tank. Many reviewers mention installing it in a closet, garage, or utility room with minimal footprint.
Electrical Requirements and Upgrade Costs
Before buying the RTEX-24, verify your electrical panel capacity. The unit draws up to 100 amps at full load across three circuits. If your home has a 100-amp service, you will likely need an electrical panel upgrade. That upgrade can cost 1,500 to 3,000 dollars depending on your area and panel type.
Homes with 200-amp service can usually accommodate the RTEX-24 without upgrades, assuming you have available breaker slots. An electrician will need to run three separate circuits to the unit location. Budget 300 to 600 dollars for electrical work if your panel is ready.
Electric vs Gas: When Electric Makes More Sense
Electric tankless units shine in homes without natural gas access, in warm climate zones, and where venting installation is impractical. If your groundwater stays above 55 degrees year-round, the RTEX-24 can match gas unit performance for typical household demand. Operating costs depend on your local electricity rates.
In areas with cheap electricity under 12 cents per kWh, electric tankless can be very economical. In regions with rates above 20 cents per kWh, gas may be cheaper to operate despite lower efficiency ratings. Check your local utility rates before deciding between gas and electric.
7. Stiebel Eltron DHX 12-2 Trend Point-of-Use Tankless – Best Premium Point-of-Use Electric
Stiebel Eltron DHX 12-2 Trend POU Electric Tankless Water Heater 12kW 240V
3 GPM
12kW
240V Electric
Point-of-Use
Made in Germany
Self-Modulating
Pros
- German engineering with premium build quality
- Fast 13-second hot water delivery in tests
- Self-modulating technology saves energy
- Anti-scalding limits with selectable temperatures
- Compact 5.5-pound design
Cons
- Limited to 3 GPM flow rate
- Requires hard wiring installation
- May need electrical panel upgrades for 12kW demand
Stiebel Eltron is a German manufacturer with decades of tankless engineering experience, and the DHX 12-2 Trend shows it. This point-of-use unit delivers hot water in about 13 seconds in independent tests. The build quality feels noticeably more premium than budget competitors, with a clean white housing and precise digital controls.
I recommend this unit for targeted applications where you need fast hot water at a specific fixture. It excels as a booster for a distant bathroom, a kitchen sink heater, or a dedicated unit for a home office wet bar. The 3 GPM flow rate is enough for a single faucet or a low-flow showerhead.
The self-modulating technology is the standout feature. Unlike cheaper units that run at full power regardless of demand, the DHX 12-2 adjusts its energy consumption based on flow rate and incoming water temperature. This means it only uses the electricity it actually needs, which translates to real energy savings.
Safety Features Worth Highlighting
The integrated AE3 safety system includes anti-scalding protection with three selectable temperature limits: 109, 122, or 131 degrees Fahrenheit. This is especially valuable in households with children or elderly family members. You can set a maximum temperature ceiling that prevents accidental burns.
The IP 24 water resistance rating means the unit is protected against water spray. This makes it suitable for bathroom installation where humidity and splash exposure are common. The unit also includes flow sensors and inlet/outlet temperature sensors for precise thermal management.
Where This Unit Fits in Your Hot Water Strategy
The DHX 12-2 Trend works best as part of a layered approach. Use it to supplement a whole-house unit for a distant fixture, or as a standalone solution for a single room. It is not designed to replace a whole-house water heater for a family.
For homes with a master bathroom located far from the main water heater, installing this unit under the sink or in a nearby closet eliminates the wait for hot water. You get instant comfort at the tap while reducing water waste from running the tap until it warms up.
8. Rheem RTEX-04T 3.5kW Point-of-Use Electric Tankless – Best Compact Point-of-Use
Rheem 3.5kW 120V Point of Use Thermostatic Tankless Electric Water Heater
0.9 GPM
3.5kW
120V Electric
Point-of-Use
Thermostatic Control
4 Pounds
Pros
- Ultra-compact up to 98 percent smaller than tank heaters
- Thermostatic temperature control in 1-degree increments
- Standard 120V connection needs no special wiring
- Lightweight 4-pound design
- Wall mount with bottom connections
Cons
- Low 0.9 GPM flow rate for single fixture use only
- Requires 30-amp double pole breaker
- Not suitable for whole-home or shower applications
The Rheem RTEX-04T is purpose-built for point-of-use applications where you need a small amount of hot water at a single fixture. At just 4 pounds and measuring about 11 by 6 by 3 inches, this unit is practically invisible once mounted. I have recommended it for bathroom sinks, wet bars, garage sinks, and office kitchens.
The 3.5kW heating element runs on standard 120V power, which means it can work with existing household wiring in many cases. You need a 30-amp double pole breaker, but no special 240V circuit. This makes installation significantly easier and less expensive than higher-powered electric units.
The thermostatic temperature control allows adjustment from 80 to 140 degrees Fahrenheit in 1-degree increments. This precision matters for applications like a bathroom sink where you want consistent, comfortable water for handwashing without scalding surprises.
As a number-one bestseller in the Water Heaters category on Amazon, the RTEX-04T has proven its appeal. The same review base as the RTEX-24 shows over 4,000 customer experiences, with most users praising the space savings and reliable point-of-use performance.
What Applications Work Best for 0.9 GPM?
The 0.9 GPM flow rate is designed for low-flow fixtures. A standard bathroom faucet aerator flows at about 1.5 GPM, but low-flow aerators reduce that to 0.5 to 1.0 GPM. With a low-flow aerator, this unit delivers consistent hot water at the sink without any lag.
This unit is not suitable for showers, which typically need 1.5 to 2.5 GPM. It cannot serve a whole home. But for a dedicated sink application, it eliminates the need to run a long pipe from your main water heater, saving both water and energy.
Installation Simplicity and Cost Savings
Because this unit runs on 120V and is designed for single-fixture use, installation costs are minimal. Many homeowners install it themselves with basic plumbing and electrical skills. The upright mounting design with bottom connections makes pipe routing straightforward.
No venting is required since it is electric. The main cost consideration is the 30-amp breaker and appropriate gauge wire from your panel. An electrician can handle this in about an hour, keeping total installation costs under 200 dollars in most cases.
9. EcoSmart POU 4T 3.5kW Point-of-Use Electric Tankless – Most Affordable Option
EcoSmart POU 4T 3.5kW 120v Thermostatic Point of Use Tankless Electric Water Heater
0.8 GPM
3.5kW
120V Electric
Point-of-Use
Thermostatic
4 Pounds
Pros
- Most affordable point-of-use tankless option
- Compact 90 percent smaller than traditional tanks
- Standard 120V connection with 30-amp breaker
- On-demand heating eliminates standby loss
- Lightweight 4-pound wall-mount design
Cons
- Mixed reliability with 3.3-star average rating
- Flow rate must be calibrated correctly for proper heating
- Limited warranty support reported by some users
- Not suitable for high-flow fixtures
The EcoSmart POU 4T is the most affordable tankless water heater in this guide. At under 130 dollars, it offers an entry point into tankless technology for budget-conscious buyers. The unit is designed for point-of-use applications similar to the Rheem RTEX-04T, with a 0.8 GPM flow rate and 3.5kW heating element.
I want to be transparent about the review data. This unit carries a 3.3-star average from 30 reviews, which is notably lower than other units in this guide. The rating distribution shows 38 percent five-star reviews but also 29 percent one-star reviews. This split tells me the product works well when properly installed but has reliability concerns for some users.
The key to success with the EcoSmart POU 4T is proper flow rate calibration. Several reviewers note that if the water flows too fast through the unit, it cannot heat adequately and delivers lukewarm water. Using a low-flow aerator is essential for acceptable performance.
Managing Expectations for a Budget Unit
At this price point, you are getting basic tankless functionality without premium features. There is no LCD display, no self-modulating technology, and limited warranty documentation. The unit heats water on demand and saves space, but you should not expect the build quality or longevity of a Stiebel Eltron or Rheem.
For applications like a garage sink, a guest bathroom that gets occasional use, or a workshop, this unit can deliver acceptable performance at a rock-bottom price. For daily-use applications in your main living areas, I recommend investing in a higher-rated unit.
When to Choose This Over a More Expensive Unit
Choose the EcoSmart POU 4T when your budget is the primary constraint and your hot water needs are minimal. It makes sense for a rarely used guest bathroom, an outdoor sink, or a secondary fixture where consistent performance is not critical.
If this is your only water heater or it will serve a daily-use fixture, the extra 100-plus dollars for the Rheem RTEX-04T is worth the investment. The higher reliability, stronger warranty support, and proven track record make a real difference over years of ownership.
10. Rinnai 223174PP Horizontal Termination Kit – Essential Venting Accessory
Rinnai 223174PP Rinnai 223174PP 8.7″ Long Horizontal Termination Kit for Condensing Tankless Water Heaters
8.7 Inch Horizontal
Stainless Steel
Condensing Compatible
Vent Termination
Lifetime Warranty
Pros
- Required for proper condensing tankless venting
- Stainless steel construction for durability
- Clean appearance for exterior wall termination
- Limited lifetime warranty from Rinnai
- Compatible with Rinnai condensing models
Cons
- Some reports of plastic inner pipe quality concerns
- May trigger error codes on certain installations
- Adds to total installation cost
The Rinnai 223174PP termination kit is not a water heater itself, but it is an essential accessory for anyone installing a Rinnai condensing tankless unit. This horizontal termination kit provides the exterior vent exit point for your condensing gas water heater. Without a proper termination kit, your installation cannot meet code requirements.
Our team includes this accessory because many buyers overlook venting components when budgeting for a tankless installation. The stainless steel exterior looks clean on an outside wall and provides proper CO2 exhaust venting. It is designed specifically for condensing tankless models that use PVC venting.
The kit measures 8.7 inches in length and includes the wall termination assembly. Installation is straightforward for a professional plumber, typically adding about 30 minutes to the total tankless installation time. The stainless steel exterior cap protects against weather and pests.
With a limited lifetime warranty from Rinnai, this termination kit is a one-time purchase that should last as long as your tankless unit. It is a small investment that ensures your venting system meets manufacturer specifications and local building codes.
Compatibility and Installation Notes
This termination kit works with Rinnai condensing tankless water heaters including the NPE series and similar condensing models. It is designed for horizontal wall penetration, which is the most common venting configuration for indoor installations. If your installation requires vertical roof venting, you need a different termination assembly.
Some users have reported an E8 error code after installation. This typically relates to improper venting slope or an issue with the inner plastic pipe seal. Having a qualified installer who follows Rinnai venting guidelines precisely prevents these issues.
Why Venting Quality Matters for Condensing Units
Condensing tankless water heaters extract so much heat from exhaust gases that the moisture condenses into liquid. This condensate is slightly acidic and requires proper drainage. The termination kit is part of a venting system that must handle both exhaust gases and condensate management.
Poor venting installation is one of the most common causes of tankless water heater problems. Investing in the correct manufacturer-approved termination kit and having it professionally installed protects your equipment warranty and ensures safe operation for years.
How to Choose the Right Tankless Water Heater
Choosing between the best tankless water heaters comes down to five key factors. I will walk you through each one so you can make an informed decision for your specific situation. The right choice depends on your fuel source availability, household size, climate, and budget.
Gas vs Electric: The First Decision
Gas tankless water heaters (natural gas or propane) generally deliver higher flow rates and perform better in cold climates. They handle whole-house demand more effectively because gas burners can produce more BTU than electric heating elements. However, they require gas line infrastructure, venting, and professional installation.
Electric tankless units are simpler to install, require no venting, and achieve near-perfect efficiency ratings. The trade-off is that they demand significant electrical capacity. Whole-home electric units like the Rheem RTEX-24 need 200-amp service and multiple dedicated circuits. Point-of-use electric units are much simpler and can run on standard household circuits.
Sizing by GPM: How Much Flow Do You Need?
Flow rate, measured in gallons per minute (GPM), determines how many fixtures a unit can serve simultaneously. Count the fixtures you might use at the same time. A shower uses about 2 GPM, a faucet uses 1 to 1.5 GPM, and a dishwasher uses about 1.5 GPM.
For a 2-bathroom home where two people might shower simultaneously, you need at least 4 to 5 GPM. For a large family with 3-plus bathrooms, look for 7 to 10 GPM units like the Rinnai RE199iN. For a single fixture, a point-of-use unit at 0.8 to 3 GPM is sufficient.
Temperature Rise and Groundwater Matters
Every tankless unit is rated at a specific temperature rise. If your groundwater enters at 50 degrees and you want 120-degree output, the unit must achieve a 70-degree rise. The colder your groundwater, the lower your effective GPM. Southern states with warm groundwater get full rated performance. Northern states see reduced flow rates in winter.
Check your local groundwater temperature before purchasing. You can find this information from your local water utility or geological survey. Subtract that number from your desired output temperature to calculate your required temperature rise. Then check the manufacturer’s flow rate chart for that rise.
Efficiency Ratings: UEF and Energy Factor
The Uniform Energy Factor (UEF) measures overall water heater efficiency. Higher numbers mean more efficient units. Gas tankless units typically range from 0.82 for non-condensing models to 0.95-plus for condensing models. Electric tankless units achieve 0.98 to 0.99 UEF because nearly all electricity converts directly to heat.
Condensing gas models cost more upfront but capture waste heat from exhaust gases, pushing efficiency above 0.90. Over a 15-year lifespan, that efficiency difference can save hundreds of dollars in operating costs. Non-condensing models are cheaper to buy but vent more heat wasted.
Total Cost of Ownership Over Five Years
Look beyond the purchase price. Installation costs vary widely: gas units need venting (300 to 600 dollars), possible gas line upgrades (200 to 500 dollars), and professional labor (500 to 1,500 dollars). Electric whole-home units may need panel upgrades (1,500 to 3,000 dollars). Point-of-use electric units have the lowest installation costs at 100 to 300 dollars.
Factor in annual maintenance. All tankless units need descaling once a year to remove mineral buildup. Professional descaling costs 100 to 150 dollars. DIY descaling kits cost about 50 dollars. In hard water areas, you may need descaling twice a year. Budget for a water softener if your water hardness exceeds 7 grains per gallon.
Hard Water Considerations
Hard water is the number one enemy of tankless water heaters. Minerals in hard water build up inside the heat exchanger, reducing efficiency and eventually causing flow restrictions. If you live in a hard water region, consider installing a whole-house water softener before your tankless unit.
Even with a softener, annual descaling is essential. The process involves circulating a descaling solution (usually white vinegar) through the heat exchanger for about 45 minutes. Units with diagnostic displays will alert you when service is needed. Without regular descaling, expect reduced performance and shorter equipment life.
FAQ
What brand of tankless water heater is the most reliable?
Rinnai is consistently rated the most reliable tankless water heater brand by both professional plumbers and homeowners. On Reddit forums like r/Plumbing and r/Plumbing, Rinnai receives the most praise for long-term durability and ease of service. Navien and Stiebel Eltron also rank highly for build quality. Rinnai models like the RE199iN and V53DeN have proven track records with thousands of satisfied owners and 15-year heat exchanger warranties.
What is the downside of tankless water heaters?
The main downsides of tankless water heaters are higher upfront costs (including the unit and professional installation), the need for annual descaling maintenance, potential gas line or electrical panel upgrades, and a brief delay before hot water reaches fixtures. In cold climates with low groundwater temperatures, effective flow rates decrease, meaning fewer simultaneous fixtures can be served. Installation costs typically run 1,000 to 3,000 dollars beyond the purchase price.
What is the best tankless water heater according to consumer reports?
Based on aggregated consumer feedback and expert reviews, the Rinnai RE199iN ranks as the best overall tankless water heater for large homes with its 9.8 GPM flow rate. For electric whole-home use, the Rheem RTEX-24 is the top seller with over 4,000 positive reviews. For budget buyers, the Rinnai V53DeN delivers reliable gas tankless performance at a lower price point.
Which is better, Rheem or Rinnai tankless water heaters?
Rinnai generally offers better long-term reliability and longer warranties (15-year heat exchanger) compared to Rheem. However, Rheem provides better value at lower price points and offers the widest range of electric options. Rinnai excels in gas tankless performance with models like the RE199iN and V53DeN. Rheem dominates the electric tankless market with the RTEX-24 and point-of-use units. Choose Rinnai for premium gas performance and Rheem for budget-friendly electric options.
How long do tankless water heaters last?
Tankless water heaters typically last 20 to 25 years with proper maintenance, compared to 10 to 15 years for traditional tank heaters. The key to longevity is annual descaling to prevent mineral buildup in the heat exchanger. Gas units with stainless steel heat exchangers (like Rinnai models) tend to last longest. Regular maintenance and water quality are the biggest factors in achieving maximum lifespan.
Final Verdict on the Best Tankless Water Heaters
After comparing 10 models across gas and electric categories, the Rinnai RE199iN stands out as the best tankless water heater overall for large homes. Its 9.8 GPM flow rate, 15-year warranty, and proven reliability make it the top recommendation for families with high hot water demand. For smaller homes and budgets, the Rinnai V53DeN delivers excellent value.
On the electric side, the Rheem RTEX-24 remains the best whole-home electric tankless option with its massive review base and 99.8 percent efficiency. For point-of-use needs, the Rheem RTEX-04T and Stiebel Eltron DHX 12-2 Trend cover both budget and premium segments effectively.
Whichever unit you choose, invest in professional installation and commit to annual descaling maintenance. These two factors determine whether your tankless water heater delivers 20 years of trouble-free service or becomes a frustrating expense. The best tankless water heaters in 2026 reward homeowners who do their research and maintain their equipment properly.