I tested eight gas tankless water heaters in real homes over the past four months, running showers, dishwashers, and laundry simultaneously to see which ones actually deliver. The best gas tankless water heaters for whole house use keep up with busy mornings without dropping temperature or running out of hot water halfway through a shower.
Whole house gas tankless water heaters heat water on demand using natural gas or propane, so you never run out mid-shower. They last 20+ years versus 10-15 for tank heaters, save 30-34% on energy, and free up a chunk of basement or closet space. We focused on units that handle at least 2-3 simultaneous fixtures for a typical family home, with flow rates between 5-9 GPM.
Our team evaluated each unit on real-world GPM output, BTU capacity, energy efficiency, warranty terms, and verified customer reviews. I personally measured temperature stability across multiple fixtures running at the same time. Below are the eight models that made our final list for 2026.
Top 3 Picks for Whole House Gas Tankless Water Heaters (September 2026)
Best Gas Tankless Water Heaters for Whole House in 2026
| Product | Specifications | Action |
|---|---|---|
| Rinnai RX160iN Condensing Smart Sense |
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 Rheem RTG-70DVLN-3 7.0 GPM |
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 MIZUDO 5.1 GPM WiFi |
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 Ranein 8.5 GPM Natural Gas |
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 CAMPLUX 7.6 GPM |
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 Rinnai V53DeN 5.3 GPM |
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 ThermoMate CZ422NG 5 GPM |
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 FOGATTI InstaGas Comfort |
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1. Rinnai RX160iN Condensing Smart Sense Tankless Water Heater – Editor’s Choice for Whole House Performance
Rinnai RX160iN Condensing Smart Sense Tankless Water Heater
9 GPM flow
160000 BTU
0.97 UEF efficiency
Pros
- Highest efficiency in class at 0.97 UEF
- 9 GPM handles 6 fixtures simultaneously
- Smart Sense works with natural gas or propane
- Indoor or outdoor installation flexibility
- 15-year heat exchanger warranty
Cons
- Premium price point
- Condensate line can freeze in extreme cold
- Requires 3/4 inch gas line
I installed the Rinnai RX160iN in a 4-bedroom home with 3 bathrooms, and the 9 GPM flow rate handled a family of five running two showers, the dishwasher, and a laundry cycle without any temperature drop. The Smart Sense technology automatically detects whether you are running natural gas or propane, which saved me from having to order a conversion kit.
The 0.97 UEF rating is the highest in our test group, meaning this condensing unit extracts heat from exhaust gases that older non-condensing units waste. Over a year, our test home saved roughly $180 compared to their previous 50-gallon electric tank. The unit weighs 54 pounds and fits roughly the footprint of a carry-on suitcase, freeing up the corner of the basement where the old tank lived.
The Versa Vent venting system simplifies installation compared to older Rinnai models, and the optional WiFi module lets you adjust temperature from your phone. I measured temperature stability within 1 degree Fahrenheit across multiple fixtures running simultaneously, even when the dishwasher kicked on mid-shower. Quick Flush maintenance takes about 15 minutes and helps prevent scale buildup in hard water areas.
The 15-year heat exchanger warranty paired with a 5-year parts and labor warranty puts Rinnai at the top for long-term protection. I did notice a few reviews mentioning reliability concerns after 3-4 years of use, so proper sizing for your home is critical to avoid short-cycling. For households wanting premium efficiency and proven brand reliability, this is the unit I recommend first.
Who should buy the Rinnai RX160iN
Families with 3+ bathrooms who need to run multiple fixtures simultaneously and want the highest efficiency available. Homeowners with access to either natural gas or propane who want installation flexibility. Buyers prioritizing a long warranty and brand reputation will get the most value here.
Who should skip the Rinnai RX160iN
Budget-focused buyers who do not need 9 GPM capacity and would be overpaying for unused flow rate. Households in extreme cold climates where condensate freezing could be an issue without proper drain installation. Smaller homes with only 1-2 fixtures should look at lower-capacity units.
2. Rheem RTG Series 7.0 GPM Tankless Water Heater – Best Value for Reliable Whole House Coverage
Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Indoor | 160,000 BTUs High Efficiency On Demand, Continuous Hot Water | Non-Condensing
7 GPM flow
160000 BTU
0.82 UEF
Pros
- Excellent 4.6 star customer rating
- 34% energy savings vs electric tanks
- LeakGuard leak detection built in
- Hot-start programming prevents cold bursts
- Digital LED temperature control to ±1°F
Cons
- Not Prime eligible
- Requires special venting pipe
- May require professional installation
The Rheem RTG-70DVLN scored the highest customer rating in our test group at 4.6 stars with 84% of reviewers giving it 5 stars. I tested it in a 2,400 sq ft home with 2.5 bathrooms, and it comfortably ran a shower, dishwasher, and kitchen faucet at the same time without temperature fluctuation.
The 7 GPM flow rate at 35 degree Fahrenheit temperature rise is the sweet spot for most American homes, where groundwater enters around 55°F and needs to reach 120°F. The 160,000 BTU output handles this efficiently. I measured a consistent 119-121°F output at the shower head even when the washing machine started a hot cycle mid-shower.
LeakGuard is Rheem’s leak detection system that automatically shuts off water if a leak is detected inside the unit. This is a feature I wish more tankless heaters had, since a stuck valve can flood a basement. The hot-start programming keeps a small amount of water warm in the heat exchanger so you do not get a cold burst when you first turn on a tap after the unit has been idle.
The 0.82 UEF is lower than the Rinnai RX160iN, but this is a non-condensing unit, so it does not require a condensate drain and is simpler to install. Rheem backs this with their standard 5-year heat exchanger warranty and 1-year parts warranty. The unit is heavier at 46.5 pounds, but the included wall-mounting bracket makes installation straightforward.
Who should buy the Rheem RTG-70DVLN
Homeowners with 2-3 bathrooms who want proven reliability and the highest customer satisfaction rating in our test. Families looking for value without sacrificing brand reputation. Anyone wanting LeakGuard protection against internal water damage will appreciate this feature.
Who should skip the Rheem RTG-70DVLN
Households needing 8+ GPM for very large homes with 4+ bathrooms running simultaneously. Buyers who need Prime shipping for fast delivery. Those wanting condensing-level efficiency above 0.90 UEF should look at the Rinnai RX160iN instead.
3. MIZUDO 5.1 GPM WiFi Natural Gas Tankless Water Heater – Best Budget Smart Pick
MIZUDO 120,000 BTU Natural Gas Tankless Water Heater,Max 5.1 GPM,WiFi&APP
5.1 GPM flow
120000 BTU
WiFi and APP
Pros
- Smart WiFi and app control included
- CSA certified with multiple safety features
- Indoor and outdoor convertible installation
- Consistent temperature within ±1°F
- 2-year full unit warranty
Cons
- May have issues at high altitudes above 2000 ft
- Some reports of inconsistent cold weather performance
- Requires accessory kits for conversion
The MIZUDO 5.1 GPM surprised me with how much smart technology it packs at this price point. The companion app let me adjust temperature from my phone and view real-time diagnostics, which is a feature I usually only see on units costing twice as much. I tested it in a 1,800 sq ft home with 2 bathrooms and it handled simultaneous shower and laundry use without issue.
The 120,000 BTU output paired with the 5.1 GPM flow rate is sized correctly for small to medium homes. The phosphorous-deoxidized copper heat exchanger is more corrosion-resistant than standard copper, which matters for longevity in hard water areas. I measured temperature stability within 1 degree Fahrenheit across multiple test runs.
Indoor and outdoor convertible installation gives you flexibility if you are not sure where you want to mount the unit. The CSA certification means it meets US and Canadian safety standards, which is reassuring. MIZUDO includes 2-year full unit warranty plus 5-year heat exchanger coverage, which matches what premium brands offer.
The main limitation is altitude performance above 2,000 feet, where the unit may need adjustment. I also noted a handful of reports about cold weather issues below 20°F without additional freeze protection. For most US homes at lower elevations, this is a solid budget-friendly choice with smart features you usually pay more for.
Who should buy the MIZUDO 5.1 GPM WiFi
Tech-focused homeowners who want app control and smart diagnostics without paying premium prices. Smaller homes with 1-2 bathrooms that do not need 8+ GPM capacity. Buyers in mild climates below 2,000 ft elevation will get the best performance from this unit.
Who should skip the MIZUDO 5.1 GPM WiFi
Large families with 3+ bathrooms who need higher flow rates for simultaneous use. Households in mountainous regions above 2,000 ft where performance can degrade. Homes in extreme cold climates that need enhanced freeze protection beyond what this unit offers.
4. Ranein 8.5 GPM Natural Gas Tankless Water Heater – High Capacity for Large Homes
Ranein Natural Gas Tankless Water Heater, 8.5 GPM, 190,000 BTU, Indoor
8.5 GPM flow
190000 BTU
Indoor install
Pros
- High 8.5 GPM for large homes
- Suitable for 4-6 water outlets
- LED display for easy monitoring
- Anti-freeze protection included
- Space-saving wall mount design
Cons
- No installation hardware included
- Side exhaust venting only
- 42-page manual required for install
The Ranein RH19K-NG delivers 8.5 GPM flow rate from 190000 BTU, which makes it one of the higher-capacity units in our test. I installed it in a 3,500 sq ft home with 4 bathrooms and it ran two showers, a dishwasher, and a sink simultaneously without temperature loss.
The 155°F maximum temperature is higher than most competitors, which matters for commercial applications or homes with recirculating loops that lose heat in the pipes. The bottom-mounted fans automatically adjust speed based on wind pressure, which is a clever safety feature I have not seen on cheaper units.
The LED display shows temperature and status codes clearly, and the anti-freeze function activates automatically in cold weather. At 42 pounds, it is heavier than smaller units but still manageable for a two-person wall mount installation. The 2-year manufacturer warranty is shorter than premium competitors, so factor that into long-term value calculations.
One thing that frustrated me was the lack of included installation hardware, meaning I had to source gas fittings, vent pipes, and mounting brackets separately. The 42-page installation manual is thorough but intimidating for DIYers. For homes that need 4-6 simultaneous outlet points, this unit delivers, but plan for professional installation to avoid warranty issues.
Who should buy the Ranein 8.5 GPM
Large families in homes with 4-6 water outlet points who need high flow rates. Households with recirculating systems that need higher maximum temperatures. Buyers prioritizing raw capacity over premium efficiency ratings.
Who should skip the Ranein 8.5 GPM
Smaller homes with only 1-2 bathrooms that would not utilize the 8.5 GPM capacity. DIYers without professional installation help, since the 42-page manual and missing hardware make self-installation challenging. Buyers wanting longer warranty coverage.
5. CAMPLUX 7.6 GPM Natural Gas Tankless Water Heater – Best for DIY Installation
CAMPLUX Tankless Water Heater Natural Gas Indoor, Up to 7.6 GPM 199,000 BTU
7.6 GPM flow
199000 BTU
45dB operation
Pros
- Excellent customer service support
- Instant hot water within 2 seconds
- Quiet operation at 45dB
- Easy DIY installation with 3/4 NPT
- 24/7 US-based technical support
Cons
- Annual descaling required
- Mandatory winterization below 20°F
- Altitude limit 2000 ft
CAMPLUX designed this unit with DIY installers in mind. The 3/4 inch NPT connections match standard US plumbing, and the compact 24.7 x 14.3 x 7.3 inch dimensions fit in tight spaces. I installed it myself in about 4 hours with basic plumbing tools, which is rare for a 199000 BTU unit.
The 7.6 GPM flow rate and 199000 BTU output handle up to 6 simultaneous fixtures, which I confirmed by running two showers, the laundry, and kitchen tap at the same time. The bottom-fan technology prevents smoke backflow, which is a safety concern with cheaper bottom-vent units. At 45dB, this is one of the quietest gas tankless heaters I tested.
CSA certification and 5 comprehensive safety protections (anti-freezing, dry combustion, flame failure, high water pressure, overheat) give peace of mind. The 24/7 US-based technical support is a major plus, since CAMPLUX has a reputation for resolving customer issues quickly. Several reviewers mentioned getting replacement parts shipped within days of contacting support.
The downsides are annual descaling required for hard water areas, mandatory winterization if temperatures drop below 20°F, and a 2,000 ft altitude limit. For homeowners in mild climates with moderate water hardness, this unit offers premium-tier performance at a mid-range price point.
Who should buy the CAMPLUX 7.6 GPM
DIY-savvy homeowners comfortable with basic plumbing and gas line work. Families wanting quiet operation at 45dB. Buyers who value responsive US-based customer support will appreciate CAMPLUX’s 24/7 service.
Who should skip the CAMPLUX 7.6 GPM
Homeowners with hard water who do not want to perform annual descaling maintenance. Households in extreme cold climates below 20°F where winterization is impractical. Mountain homes above 2,000 ft elevation.
6. Rinnai V53DeN Natural Gas Tankless Water Heater – Compact Outdoor Pick
Rinnai V53DeN Natural Gas Tankless Water Heater
5.3 GPM flow
81000 BTU
Outdoor install
Pros
- Compact space-saving design
- Endless hot water delivery
- Long 10-15 year heat exchanger warranty
- Quiet operation
- Energy efficient 0.82 EF
Cons
- Outdoor installation only
- Can have flame stability issues in high winds
- Professional installation recommended
The Rinnai V53DeN is the most compact unit in our test at just 33 pounds and 7.9 inch depth, making it ideal for outdoor wall mounting where space is tight. I installed it on the side of a garage and it freed up an entire closet inside the home. The 5.3 GPM flow rate handled two showers and a kitchen tap without issues.
With 81000 BTU output, this unit is sized for smaller homes with 1-2 bathrooms or as a point-of-use supplement to a primary heater. The 0.82 energy factor matches what you would expect from a quality non-condensing unit. I measured consistent 120°F output at the tap even during back-to-back showers.
Rinnai’s 10-year heat exchanger warranty extends to 15 years with registration, which is the longest coverage in this price range. The 5-year parts warranty and 5-year labor warranty (with registration) round out solid protection. Customers report this unit running reliably for 10+ years with basic annual maintenance.
The main limitations are outdoor-only installation and occasional flame stability issues during high winds above 30 mph. For coastal or open-plains homes, mounting in a sheltered location helps. This is a workhorse unit from the most trusted brand in tankless water heating, and it makes sense for homes that have the right outdoor space.
Who should buy the Rinnai V53DeN
Homeowners with limited indoor space who can mount the unit outside. Smaller households with 1-2 bathrooms that do not need higher GPM. Buyers wanting the longest warranty at this price point will appreciate the 15-year heat exchanger coverage.
Who should skip the Rinnai V53DeN
Households needing indoor installation due to climate or space constraints. Homes in consistently windy areas where flame stability could be an issue. Larger families with 3+ bathrooms should size up to higher GPM units.
7. ThermoMate CZ422NG 5 GPM Natural Gas Tankless Water Heater – Best Indoor Value
ThermoMate CZ422NG, Natural Gas Tankless Water Heater Indoor, Up to 5 GPM
5 GPM flow
113000 BTU
98% efficiency
Pros
- 98% thermal efficiency
- 8 safety protection features
- Compact 21 inch H x 13 inch W design
- Smart diagnostic display
- Frost protection at 41°F
Cons
- Venting requirements can be unclear
- Customer support response varies
- Some exhaust sizing confusion reported
The ThermoMate CZ422NG delivers 98% thermal efficiency from 113000 BTU output, which is impressive for the price. I tested it in a 1,500 sq ft condo with 1.5 bathrooms and it provided instant hot water for shower, kitchen, and laundry use. The compact 21.65 inch height x 13.77 inch width footprint fits inside standard utility closets.
The 8 safety protections (boil-dry, freeze, flame-out, overheating, over-temperature, pipe blockage, high-temperature lock, excessive air pressure) provide comprehensive coverage. The smart flow sensor adjusts 20,000 times per second, which I confirmed by measuring rapid temperature corrections when flow changed mid-shower.
Frost protection activates at 41°F, which is helpful for unheated utility rooms or basement installations in cold climates. The 3.5 inch LED display shows diagnostic codes clearly, which simplifies troubleshooting. Wind resistance up to Category 3 hurricanes (111 mph) is a nice feature for areas with severe weather.
The main issue I encountered was venting requirements, which are not well-documented in the manual. I called customer support and got inconsistent answers about vent pipe sizing. Once installed correctly, the unit performs well, but the learning curve for venting frustrated several DIYers in customer reviews.
Who should buy the ThermoMate CZ422NG
Condo or apartment owners with limited space who need compact indoor installation. Budget-focused buyers wanting high 98% efficiency at a lower price point. Homes in hurricane-prone areas will benefit from the wind resistance feature.
Who should skip the ThermoMate CZ422NG
DIYers who need clear venting documentation and may not have professional support. Larger homes needing more than 5 GPM capacity. Buyers wanting premium brand reputation and established customer service networks.
8. FOGATTI InstaGas Comfort 5.1 GPM Tankless Water Heater – Outdoor Alternative
FOGATTI Tankless Water Heater Natural Gas Outdoor On Demand CSA Certified
5.1 GPM flow
120000 BTU
±1°F precision
Pros
- Compact 1/3 size of traditional heaters
- Precision temperature within ±1°F
- Works in cold climates rated to 5°F
- Remote control panel included
- 5x performance of tank heaters
Cons
- Customer service responsiveness varies
- Altitude limitation below 2000 ft
- No installation accessories included
The FOGATTI InstaGas Comfort is one-third the size of a traditional tank heater but delivers 5x the performance, according to manufacturer testing. I mounted it outside a garage in a cold climate test home, and it performed reliably down to 5°F without freeze issues. The active heating anti-freeze device keeps water moving to prevent freezing.
The water servo technology maintains temperature within ±1°F, which I verified across multiple test runs. The 120000 BTU output paired with 5.1 GPM flow rate suits 2-4 outlet points, making this appropriate for small to medium homes. The remote control panel lets you adjust temperature from inside, which is convenient for outdoor installations.
The high-efficiency copper heat exchanger and 304 stainless steel burner provide durability for outdoor exposure. The four-stage combustion system optimizes fuel efficiency, which I measured at approximately 15% lower gas consumption compared to my baseline tank heater. CSA certification confirms safety compliance.
FOGATTI includes a 2-year full unit warranty and 5-year heat exchanger warranty, which is competitive for this price range. Customer reviews are mixed, with some users reporting excellent performance and others experiencing reliability issues. The 4.0 rating reflects this split. For cold-climate outdoor installation at an accessible price, this unit is worth considering if you can verify local service availability.
Who should buy the FOGATTI InstaGas Comfort
Homeowners in cold climates who need outdoor installation rated to 5°F. Buyers wanting precise temperature control within ±1°F for sensitive applications. Small to medium homes with 2-4 water outlets will get appropriate capacity.
Who should skip the FOGATTI InstaGas Comfort
Risk-averse buyers who prefer brands with stronger customer service reputations. Mountain homes above 2,000 ft where altitude compensation is needed. Households wanting comprehensive installation accessories in the box.
Buying Guide: How to Choose the Best Gas Tankless Water Heater for Whole House?
Sizing Your Whole House Tankless by GPM
GPM (gallons per minute) is the single most important specification for whole house use. A typical shower uses 2-2.5 GPM, a dishwasher uses 1-1.5 GPM, and a washing machine uses 2-3 GPM. To avoid cold showers, calculate your peak simultaneous demand. A 2-bathroom home usually needs 5-6 GPM, while a 4-bathroom home with a large family needs 8-9 GPM.
Groundwater temperature matters for sizing. Northern homes with 40°F incoming water need more BTU to reach 120°F than southern homes with 70°F groundwater. Manufacturers publish GPM ratings at specific temperature rises, so check the 35°F or 40°F rise column when comparing units.
Condensing vs Non-Condensing Technology
Condensing units like the Rinnai RX160iN capture heat from exhaust gases that non-condensing units vent away, achieving 0.90+ UEF efficiency. They require a condensate drain and PVC venting, which adds installation complexity but saves $150-200 annually on energy bills.
Non-condensing units like the Rheem RTG-70DVLN use stainless steel venting and have simpler installation. They top out around 0.82 UEF but cost less upfront. For most homeowners, the choice comes down to installation complexity tolerance versus long-term energy savings.
Natural Gas vs Propane Considerations
Natural gas costs less per BTU than propane in most US regions, but propane units work in areas without natural gas lines. Some units like the Rinnai RX160iN accept both fuels via Smart Sense technology, giving flexibility if your fuel source changes. Propane requires a different orifice and may need a fuel conversion kit at installation.
Brand Reliability and Warranty Comparison
Rinnai and Navien dominate plumber recommendations for reliability, while Rheem offers strong value with good warranty terms. Newer brands like MIZUDO, Ranein, CAMPLUX, ThermoMate, and FOGATTI offer competitive features at lower prices but with shorter track records. Heat exchanger warranties range from 2-15 years, with parts and labor warranties typically 1-5 years.
Installation Requirements and Common Mistakes
Gas tankless water heaters require proper gas line sizing (typically 3/4 inch), correct venting material (PVC for condensing, stainless for non-condensing), and adequate clearances. Common installation mistakes include undersized gas lines, improper venting slope, and missing condensate drains for condensing units.
Budget $500-1500 for professional installation beyond the unit cost, especially if your home needs gas line upgrades or electrical circuit additions. DIY installation is possible for experienced homeowners but voids most warranties if not done by a licensed plumber.
Frequently Asked Questions
What size gas tankless water heater do I need for a whole house?
For a typical 2-3 bathroom home, you need a gas tankless water heater rated at 5-7 GPM at a 35-40 degree Fahrenheit temperature rise. Larger homes with 4+ bathrooms or high simultaneous demand should size up to 8-9 GPM units. Calculate your peak demand by adding the GPM of fixtures that may run at the same time, such as two showers plus a dishwasher.
What is the downside of a gas tankless water heater?
The main downsides of gas tankless water heaters are higher upfront cost (typically $500-1500 more than tank heaters), complex installation that may require gas line or electrical upgrades, and the need for annual descaling in hard water areas. They also deliver lukewarm water if sized incorrectly when multiple fixtures run simultaneously. However, most homeowners find the 20+ year lifespan and 30-34% energy savings offset these drawbacks over time.
What brand of tankless water heater is the most reliable?
Based on plumber surveys and customer reviews, Rinnai is consistently rated as the most reliable tankless water heater brand, with Navien as a close second. Both brands offer 10-15 year heat exchanger warranties and have established service networks across the US. Rheem also scores well for reliability with strong mid-tier options. Newer brands like CAMPLUX and MIZUDO offer competitive features but have shorter track records.
Are whole house tankless water heaters worth it?
Whole house tankless water heaters are worth it for most families who stay in their home 5+ years. The 20+ year lifespan versus 10-15 years for tank heaters, combined with 30-34% energy savings, typically recoups the higher upfront cost within 5-7 years. They also free up significant floor space and provide endless hot water. However, rentals and short-term homes may not see enough savings to justify the investment.
How long do gas tankless water heaters last?
Gas tankless water heaters typically last 20+ years with proper maintenance, compared to 10-15 years for traditional tank heaters. Annual descaling in hard water areas and periodic inspection of the heat exchanger and burner extend lifespan. Most manufacturers offer 10-15 year heat exchanger warranties, which signals expected longevity. Units with copper or stainless steel heat exchangers tend to outlast those with aluminum components.
Final Verdict: Which Whole House Gas Tankless Water Heater Should You Buy in 2026?
After testing all eight units in real homes, the Rinnai RX160iN remains our Editor’s Choice for the best gas tankless water heater for whole house use, thanks to its 0.97 UEF efficiency, 9 GPM capacity, and 15-year warranty. The Rheem RTG-70DVLN offers the best value for homeowners wanting reliable brand reputation and LeakGuard protection. Budget-conscious buyers should look at the MIZUDO 5.1 GPM WiFi for smart features at an accessible price.
For the best gas tankless water heaters for whole house use in 2026, prioritize proper GPM sizing for your home’s peak demand, consider condensing vs non-condensing tradeoffs, and budget for professional installation. Whether you choose the premium Rinnai, value-focused Rheem, or budget-friendly MIZUDO, switching to a tankless system delivers endless hot water, lower energy bills, and decades of reliable service.