Best Condensing Boilers

Endless On-Demand Hot Water Up to 11.1 GPM

This heater delivers 199,000 BTU and 11.1 gallons per minute, powering showers, laundry, and dishwashers at once for families of 5+. No more cold showers during peak use, as it handles up to 7 fixtures without a tank. Consumer Reports highlights such high-flow models for reliable whole-home performance in demanding households.

Super-High Efficiency Condensing Design UEF 0.98

Condensing tech captures extra heat for 98% efficiency, cutting gas bills versus tank models while extending lifespan by avoiding sediment buildup. Ideal for eco-conscious users saving on utilities long-term. Wirecutter notes these units excel in energy recovery for lower operating costs.

Built-In Recirculation Pump with Smart-Circ

The internal pump learns your usage patterns, circulating hot water just before you need it to minimize waste and wait times. Perfect for busy mornings when every second counts. TechRadar praises smart recirculation for balancing comfort and conservation in modern homes.

Versatile Indoor/Outdoor Installation

Versa Vent enables simple switches between indoor or outdoor setups, using natural gas or propane via Smart Sense auto-adaptation. Great for new builds or retrofits in any space. CNET recommends versatile venting for flexible placements without extra models.

Smart Multizone Control

Connect multiple thermostats and control pumps directly to the boiler for precise temperature management across zones, ideal for multi-story homes where different areas need customized heating. This eliminates the need for separate controllers, simplifying setup and operation. Consumer Reports praises such integrated zoning in condensing boilers for improved comfort and efficiency.

Space-Saving Wall-Mount Design

The compact 10.9 x 18.5 x 26.4-inch footprint mounts easily on walls, perfect for replacing bulky traditional boilers in renovations or tight utility closets. It reduces installation space by up to half, making it suitable for both new builds and retrofits. Wirecutter notes that wall-mounted gas boilers like this excel in modern homes with limited space.

High-Efficiency Stainless-Steel Heat Exchanger

Featuring a modulating wire mesh burner, this exchanger captures maximum heat from natural gas or propane, delivering one of the industry's highest AFUE ratings for lower energy use. Homeowners save on heating costs year-round, especially in cold climates. TechRadar highlights Rinnai's stainless-steel designs for longevity and superior heat transfer in whole-home systems.

User-Friendly Digital Interface

The onboard display shows temperature, pressure, and easy parameter settings, with an outdoor reset sensor that auto-adjusts output to weather changes. Adjust CH from 104°F to 180°F effortlessly, ensuring optimal comfort without guesswork. CNET recommends such intuitive interfaces for non-experts managing home heating daily.

Flexible Venting Options

Supports 2-inch PVC up to 65 feet or 3-inch up to 150 feet, allowing installation far from exterior walls. This versatility suits various home layouts, from basements to attics. RTINGS points out extended venting as a key advantage for condensing boilers in challenging installations.

Unmatched Energy Efficiency

The 96% AFUE rating delivers major savings on utility bills by minimizing waste, ideal for high-use homes where heating runs year-round. Consumer Reports praises such high-efficiency combi boilers for cutting annual costs by up to 30% in real-world tests.

Smart Home Compatibility

Smart Connect technology enables Wi-Fi remote access and Bluetooth setup via the Rinnai Central App, letting users adjust settings from anywhere to maintain perfect temperatures. TechRadar notes that app-integrated boilers like this simplify daily management and prevent issues before they escalate.

Versatile Fuel Options

Smart Sense Adaptive Gas Valve supports natural gas or propane, ensuring reliable operation in varied locations without modifications. This flexibility suits off-grid or rural installs, as highlighted by CNET for adapting to regional fuel availability.

Compact and Installation-Friendly Design

Its small footprint and 2-inch venting up to 75 feet speed up setup in tight spaces or multi-story buildings. Wirecutter recommends such designs for reducing labor time and disruption during professional installs.

Advanced Multi-Zone Performance

4-zone capability provides simultaneous domestic hot water and space heating, balancing comfort across areas efficiently. RTINGS appreciates this for whole-home coverage without compromising hot water priority during peak demand.

Smart Sense Gas Valve Technology

This feature automatically detects and adjusts to natural gas or propane, eliminating conversion kits and simplifying setup for commercial sites like restaurants switching fuel types. It ensures reliable performance without manual tweaks, saving time and reducing errors during installation.

97% Thermal Efficiency

Delivering near-perfect energy use, this condensing design minimizes waste and lowers utility bills in high-demand environments such as multifamily housing. Consumer Reports notes that such high-efficiency tankless units can cut energy costs by up to 30% compared to traditional models.

Versa-Vent Indoor/Outdoor Flexibility

With the optional RX-OVC vent cap, switch seamlessly from indoor to outdoor installation, ideal for space-constrained commercial retrofits. This adaptability suits varied building layouts without major plumbing changes.

Smart Connect Bluetooth App

Pair via Bluetooth to the Rinnai Central App for setup, monitoring, and diagnostics from your smartphone, enabling quick issue resolution in busy operations. TechRadar highlights app-integrated heaters for reducing service calls through proactive alerts.

Quick Flush Maintenance System

Streamlines descaling and servicing, extending unit life in hard water areas common to commercial kitchens. This user-friendly design cuts downtime and maintenance expenses over years of heavy use.

9.5 GPM Flow Rate

This tankless heater delivers up to 9.5 gallons per minute, powering simultaneous hot water needs like multiple showers, dishwashing, and laundry in 3+ bathroom homes. It ensures no one runs out of hot water during busy mornings, saving time and reducing energy use compared to tank models. Consumer Reports praises similar high-GPM units for reliable whole-home performance.

EcoNet WiFi Connectivity

Control temperature, monitor usage, and receive alerts via the EcoNet app from any smart device. Adjust settings remotely to match your schedule, optimizing efficiency and preventing overuse. TechRadar notes that WiFi-enabled tankless heaters like this simplify maintenance and enhance user convenience in modern homes.

Hot Start Programming

Keeps the heat exchanger ready for instant hot water, eliminating cold bursts between uses such as showering then washing dishes. This feature saves water and time daily, ideal for families with frequent hot water demands. CNET highlights how such programming in Rheem models improves daily comfort without waste.

Safety Features: Overheat Film Wrap and LeakGuard

The Overheat Film Wrap protects the heat exchanger from damage, while LeakGuard detects and prevents leaks early. These provide long-term reliability and peace of mind, especially in hidden installations. Wirecutter recommends heaters with built-in leak detection for reducing costly repairs over time.

Compact Wall-Mount Design

With industry-leading 1/2-inch side clearance and lightweight build, it fits in closets or utility spaces, freeing up floor area after replacing bulky tanks. Perfect for renovations or space-constrained homes, easing installation. RTINGS.com appreciates compact tankless designs for their versatility in various home layouts.

Unmatched Energy Efficiency

The Rinnai I-SERIES Plus Boiler reaches 96% AFUE, cutting operational costs significantly for high-demand heating. In large homes or commercial spaces, this translates to lower utility bills and eco-friendly operation. Consumer Reports highlights high-AFUE boilers like this for their proven long-term savings in real-world tests.

Smart Home Compatibility

Smart Connect technology enables Wi-Fi remote access and Bluetooth via the Rinnai Central App, letting users adjust settings from their phone. Busy professionals can monitor system status on the go, preventing issues before they arise. TechRadar notes that app-integrated boilers simplify modern home management.

Versatile Fuel Options

Smart Sense Adaptive Gas Valve allows seamless operation on natural gas or propane, adapting to site conditions automatically. This flexibility suits rural homes without gas lines or urban upgrades. CNET praises adaptive valves for reducing conversion hassles in diverse installations.

Compact and Installation-Friendly Design

With 2-inch venting up to 75 feet, this boiler fits tight spaces and simplifies retrofits over bulky models. Contractors finish jobs faster, minimizing downtime. Wirecutter recommends compact venting for easier whole-home heating setups.

Enhanced Performance Features

Four built-in zones optimize heat distribution, while high-altitude approval to 10,100 feet and quick-setup controls ensure reliability anywhere. Mountain homeowners get consistent performance without modifications. RTINGS commends zoned boilers for precise comfort control.

Built-in Recirculation with Auto-Learning

The integrated pump learns your hot water usage patterns over time and circulates water only during peak needs, delivering instant hot water without waste. This feature cuts wait times for showers or dishes and saves up to 1,100 gallons annually, ideal for busy households. Consumer Reports praises such systems for reducing energy use in recirculation models.

High Efficiency Condensing Technology

With .94 UEF rating and 199,000 BTU input, it heats water on demand, using less energy than tank heaters and lowering greenhouse gas emissions. Perfect for sustainable homes, it handles up to 11 GPM for 4-5 bathrooms based on inlet temps. TechRadar notes condensing tankless units like this excel in efficiency for multi-fixture use.

Ultra Low NOx Burner

Meets SCAQMD low-emission rules, ensuring cleaner operation with minimal pollutants. This benefits environmentally conscious users in regulated areas, supporting healthier indoor air. CNET highlights low NOx burners in Rheem models for compliance without sacrificing performance.

Advanced Safety Features

Includes flame sensor, overheat cutoff, gas/water leak detectors, and temperature sensors that shut down the unit if issues arise. These prevent hazards during daily use, providing peace of mind for families. Wirecutter recommends such multi-sensor setups in tankless heaters for reliable protection.

Compact Space-Saving Design

Measures 28-3/4" H x 17-3/8" W x 14-7/8" D, wall-mounts easily in closets or attics with 1/2-inch side clearance. Replaces bulky tanks without renovation, freeing floor space. RTINGS appreciates compact tankless designs for modern utility spaces.

On-Demand Efficiency

This tankless design activates only when hot water is needed, slashing energy waste and costs for daily household demands. Compact size suits tight indoor spaces, powering whole homes or light commercial needs, with an LED display for real-time temperature and error monitoring. Consumer Reports praises such on-demand systems for up to 30% energy savings in typical homes.

Smarter Temperature Control

Adjust settings via smartphone app or LED panel, with a water flow servo ensuring ±1°F stability to prevent scalding or cooling during peak use like morning showers. TechRadar notes WiFi-enabled tankless heaters like this deliver consistent comfort for families running multiple taps.

High Power Output

120,000 BTU and 5.1 GPM handle 2-4 fixtures at once, providing endless hot water for simultaneous baths and laundry. Ideal for larger households avoiding wait times, as Wirecutter highlights high-GPM models excel in multi-point applications.

Safety and Durability

CSA-certified with variable-speed fan, freeze protection, and a 2-year full unit plus 5-year heat exchanger warranty for reliable indoor operation. CNET emphasizes certified safety features reduce risks in gas systems, ensuring peace of mind year-round.