BEST Commercial Tankless Water Heaters: Top 10 Picks

The best commercial tankless water heaters deliver on-demand hot water and significant energy savings for businesses prioritizing efficiency and consistent performance. Choosing the right model hinges on understanding crucial factors like flow rate, energy efficiency ratings, and venting requirements, as a mismatch can lead to costly underperformance or wasted resources. Market variations mean that not all units offer the same robust durability or precise temperature control essential for commercial settings.

With numerous options available, identifying the unit that balances power, longevity, and operational cost is paramount for uninterrupted service. Explore our curated list of top-tier commercial tankless water heaters to find the perfect fit for your enterprise’s needs.

For commercial applications, the best commercial tankless water heater selection often prioritizes high flow rates and efficient gas or propane operation, as seen in models like the Rinnai CX199iN Condensing Smart Sense or the Rheem RTGH Series which can provide up to 8.4 GPM. Electric options such as the Rheem 18kW 240V offer precise temperature control, making them a reliable choice for consistent on-demand hot water needs.

Best Commercial Tankless Water Heater: Top Picks

Image	Product	Buy
Best Pick 1	Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Commercial gas applications	Check Price
Best Pick 2	NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Commercial gas upgrades	Check Price
Best Pick 3	Rheem 18kW 240V Tankless Electric Water Heater, Gray Best for: Electric whole-house	Check Price
Best Pick 4	Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY Best for: Residential electric needs	Check Price
Best Pick 5	Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Best for: Gas whole-house	Check Price

How We Picked

We rigorously evaluated commercial tankless water heaters, prioritizing build quality, real-world performance, and durability. Our selection focused on models boasting robust construction, like the Rinnai and Rheem units, and those offering advanced features such as self-modulation and smart controls. We ruled out units with consistently lower flow rates or less adaptable venting, focusing on capacity and versatility for demanding commercial environments.

Safety was paramount, influencing our choice of models with reliable ignition and temperature management. This process led us to identify the best commercial tankless water heater options available as of 2026.

What Most Buyers Get Wrong

Sizing for Peak Commercial Demand

Commercial applications demand careful GPM (gallons per minute) consideration. Oversizing leads to wasted energy, while undersizing results in lukewarm water during peak usage. For a business needing continuous hot water, like a busy restaurant or a multi-stall barbershop, prioritize units like the Rheem RTGH Series offering up to 8.4 GPM.

For smaller operations with less simultaneous demand, models like the Rheem RTG-70DVLN-3 or RTG-70XLN-3 providing 7.0 GPM might suffice. Always calculate your simultaneous hot water needs.

Venting Flexibility for Any Commercial Space

Commercial spaces often have unique installation constraints. The ability to vent a tankless water heater indoors or outdoors significantly simplifies installation and broadens placement options. The Rinnai CX199iN and RX199iN models explicitly mention this One Model, Anywhere capability with their Versa Vent system, which is a crucial feature for commercial environments where dedicated outdoor access might not be readily available.

This flexibility ensures you can find a suitable spot without complex ductwork.

1. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane

Best for: Ideal for medium-sized commercial operations.

With a 96% efficiency rating and 199,000 BTU output, the Rinnai CX199iN delivers substantial heating power with optimized energy use, allowing for consistent hot water delivery even during peak demand. Its Smart Sense gas control system adapts to either natural gas or propane, offering significant operational cost reduction and installation flexibility.

This model boasts a maximum flow rate of 11.1 GPM and can reach temperatures up to 185°F, ensuring it meets the demands of multiple fixtures simultaneously. It operates on 120 volts with 600 watts, and its wall-mount design saves valuable commercial space. The unit is compatible with smart home systems for enhanced control.

Pros

• 96% efficiency for lower energy bills
• 199,000 BTU output for high demand
• Smart Sense gas control for fuel flexibility
• 11.1 GPM flow rate for multiple fixtures

Cons

• Requires RX-OVC vent cap for outdoor installation, adding a potential extra purchase.

Businesses needing a versatile and energy-efficient water heating solution will appreciate this Rinnai unit. It’s perfect for establishments that can utilize either natural gas or propane and require consistent hot water for multiple uses.

2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane

Best for: Compact and efficient for smaller commercial spaces.

The NEW Rinnai RX199iN offers a high thermal efficiency with a UEF of .98, translating to significant energy savings for your business. Its compact, suitcase-sized design means it fits almost anywhere, providing up to 11.1 GPM without consuming excessive commercial space.

This unit delivers a robust 199,000 BTU heat output while maintaining a high efficiency rating. It operates at 120 volts with 98 watts and supports a hot water flow rate of 11 GPM, capable of supplying about 7 fixtures concurrently. The maximum temperature reaches 140°F.

Pros

• High efficiency (UEF .98) for cost savings
• Compact design saves valuable space
• 11.1 GPM flow rate for simultaneous use
• Smart Sense gas control system

Cons

• Maximum temperature is limited to 140°F, which might be insufficient for some commercial applications.

This Rinnai is an excellent choice for smaller commercial operations or satellite locations where space is a premium. It provides ample hot water for a few simultaneous uses efficiently.

3. Rheem 18kW 240V Tankless Electric Water Heater, Gray

Best for: High-performance electric heating for demanding applications.

The Rheem 18kW 240V electric tankless water heater provides 18 kW of power, enabling it to deliver hot water flow rates of up to 4.4 GPM. Its advanced self-modulation technology precisely matches energy output to demand, ensuring optimal energy use and consistent temperatures for your commercial needs.

Featuring durable copper immersion heating elements, this unit offers a maximum temperature of 140°F and a remarkable 99.8% efficiency. It operates on 240 volts with a high wattage of 18000 watts and supports a maximum pressure of 150 PSI. The wall-mount design facilitates straightforward installation.

Pros

• 18kW power for high-volume hot water
• Up to 4.4 GPM flow rate
• 99.8% energy efficiency
• External digital thermostatic control with LED display

Cons

• Requires a 240V electrical connection and substantial amperage, potentially needing electrical upgrades.

This electric model is best suited for commercial settings requiring a significant, reliable source of hot water without the need for gas lines. It’s ideal for facilities where consistent temperature and flow are crucial, like workshops or small eateries.

4. Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY

Best for: Efficient electric option for residential or light commercial use.

With a 13kW heating output and 99.8% energy efficiency, the Rheem RTEX-13 tankless electric water heater significantly reduces energy consumption. It delivers up to 4.8 GPM, making it suitable for moderate hot water demands and offering precise temperature control with its external digital display.

This unit operates on 240 volts, providing 13 KW of power. It features durable copper heating elements and allows for temperature adjustments in 1°F increments, with a maximum temperature of 140°F. The wall-mount design and included 1/2 NPT adapters simplify installation.

Pros

• 13kW heating capacity for good flow
• Up to 4.8 GPM flow rate
• 99.8% energy efficient operation
• Precise 1°F temperature control

Cons

• Flow rate may be insufficient for high-demand, multi-fixture commercial applications simultaneously.

This Rheem electric heater is a strong choice for businesses with moderate hot water needs or where gas infrastructure is unavailable. It’s practical for smaller offices, retail spaces, or single-resident dwelling units within a commercial property.

5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water

Best for: Reliable natural gas heater for 2-3 bathroom homes.

Powered by natural gas with 160,000 BTUs, the Rheem RTG-70DVLN-3 delivers up to 7.0 GPM for fast, reliable hot water, perfect for busy 2–3 bathroom homes. Its high-efficiency, non-condensing design ensures quick heating and minimizes energy waste, lowering operational costs.

This indoor unit features Hot-start Programming for reduced cold water bursts and universal venting compatibility for flexible installation. A durable metal cabinet protects the internal components, and it supports a 1/2 gas line connection for convenience. The maximum temperature output is 140°F.

Pros

• 7.0 GPM flow rate for multiple uses
• 160,000 BTU natural gas power
• High-efficiency non-condensing design
• Hot-start Programming for consistent output

Cons

• Not compatible with smart home systems for remote monitoring or control.

Businesses that utilize natural gas and need a consistent, high-flow hot water supply for up to three bathrooms will benefit from this Rheem unit. It’s a dependable choice for small inns, guesthouses, or multi-unit residential complexes.

6. Westinghouse Tankless Water Heater Electric 14kW 240V, Instant On-Demand Hot

Best for: All-purpose electric instant hot water solution.

The Westinghouse 14kW electric tankless water heater provides instant, on-demand hot water with a maximum flow rate of 3.38 GPM. Its 14kW heating system ensures readily available hot water, minimizing wait times and energy wasted on standby heating.

Operating on 240V, this wall-mount unit requires a 60-amp double-pole circuit breaker and 6 AWG wire for installation. It features a starting flow rate of just 0.5 GPM, making it efficient even for low-demand uses. The heater has a maximum temperature limit of 140°F.

Pros

• Instant on-demand 3.38 GPM flow
• 14kW heating power
• Works with Google Assistant, Alexa, and Wi-Fi
• ETL Certified for safety and quality

Cons

• Requires specific electrical setup with a 60-amp breaker, potentially leading to installation costs.

This Westinghouse model is an excellent choice for commercial applications needing a straightforward electric hot water solution for sinks or individual workstations. Its smart home compatibility adds a layer of convenience for modern establishments.

7. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water

Best for: Durable outdoor propane heater for varied climates.

The Rheem RTG-70XLP-3 offers high-efficiency liquid propane heating, delivering up to 7.0 GPM to support multiple hot water needs like showers and laundry simultaneously. Its robust metal cabinet is designed for outdoor installation, providing reliable performance in various weather conditions.

Powered by liquid propane with 160,000 BTUs, this tankless unit ensures fast, reliable hot water, reaching temperatures up to 140°F. It features Hot-start Programming, 1/2 gas line compatibility, and industry-leading side-to-side clearance for easier mounting. The unit operates on 120V.

Pros

• 7.0 GPM flow rate for multiple fixtures
• Outdoor installation for space saving
• Liquid propane fuel for versatility
• Hot-start Programming minimizes cold water

Cons

• Uses liquid propane, which can be more expensive than natural gas depending on local pricing.

This Rheem unit is ideal for commercial properties where outdoor installation is preferred or required, and liquid propane is the available fuel source. It’s suited for 2-3 bathroom scenarios or businesses needing significant hot water capacity.

8. Rinnai CU160iN Commercial Natural Gas Condensing Tankless Water Heater, Indoor

Best for: Efficient commercial gas heater with smart monitoring.

The Rinnai CU160iN commercial gas tankless water heater is designed for energy and space efficiency, heating only when necessary to conserve power. Its high-performance 9 GPM hot water flow rate ensures a powerful, constant stream, meeting the demands of commercial operations.

This indoor unit features Wi-Fi monitoring and Circ-Logic technology for smart recirculation, optimizing performance and reliability. It operates on gas power with 120 volts, delivering consistent hot water flow for demanding business needs. The venting options offer significant installation flexibility.

Pros

• 9 GPM flow rate for commercial demand
• Wi-Fi Monitoring for remote access
• Energy-saving standby heating
• Circ-Logic recirculation technology

Cons

• Specific efficiency percentage is not provided, making direct comparison difficult.

Businesses requiring a reliable, high-flow gas water heater with advanced smart features will find this Rinnai unit highly beneficial. It’s well-suited for busy restaurants, hotels, or other facilities needing consistent hot water and performance monitoring.

9. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water

Best for: Outdoor gas heater with advanced features and freeze protection.

The Rheem RTG-70XLN-3 delivers up to 7.0 GPM of hot water, powered by 160,000 BTUs of natural gas for reliable performance in 2–3 bathroom settings. Designed for outdoor installation, this model boasts freeze protection and a low activation flow rate for efficient operation.

This unit features Hot-start Programming to reduce cold water bursts and a self-diagnostic program for easy troubleshooting. With a maximum temperature of 140°F and compatibility with an EZ-link cable, it offers flexible installation and efficient operation. It supports a 1/2 gas line.

Pros

• 7.0 GPM flow rate for multiple fixtures
• Outdoor installation conserves indoor space
• Freeze protection for colder climates
• Low activation flow rate for efficiency

Cons

• Not a condensing unit, so its efficiency might be lower than condensing models in optimal conditions.

This Rheem outdoor natural gas heater is an excellent option for businesses that can install units outside and require a dependable, high-flow hot water supply. Its freeze protection makes it suitable for regions experiencing colder temperatures.

10. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120

Best for: Versatile gas heater with high flow rates.

The Rheem RTGH Series unit provides a flexible flow rate from 0.4 to 8.4 GPM, with Exclusive Hot Start Programming ensuring consistent hot water output. Its 157,000 BTU heating capacity is suitable for a range of commercial and residential applications requiring rapid hot water.

This unit operates on fuel power with 120 volts and has a maximum temperature setting of 140°F. It features an Electric Ignition for reliable startup and Overheat Film Wrap for enhanced safety. The compact dimensions with a width of 17-11/16 inches facilitate wall mounting.

Pros

• Broad flow rate from 0.4 to 8.4 GPM
• Exclusive Hot Start Programming
• 157,000 BTU heating output
• Electric ignition for reliable starting

Cons

• Warranty terms are limited, with 1 year for labor and 5 years for parts.

This Rheem RTGH Series model is a versatile choice for businesses needing adjustable flow rates and reliable hot water. It’s well-suited for a variety of uses, from small cafes to multi-bathroom rental properties where consistent performance is key.

BTU vs. GPM: The Critical Miss for Tankless Buyers

The single most important factor when selecting a best commercial tankless water heater is not whether it’s condensing or non-condensing, nor its specific venting configuration, but rather the precise relationship between its BTU output and its Gallons Per Minute (GPM) rating, tailored to your highest simultaneous demand. Too many overlook this, leading to inconsistent hot water and premature replacement. For example, while the Rheem RTEX-13 Residential Tankless Water Heater boasts a notable 13kW electric draw, its practical GPM is inherently limited compared to high-BTU gas units, making it unsuitable for multiple high-demand fixtures operating at once, regardless of its precise temperature accuracy.

Its durability with copper immersion elements is a plus, but it cannot overcome the fundamental flow rate constraint presented by its power input when compared to units designed for more substantial hot water needs.

Consider the stark difference in capability: units like the Rheem RTG-70DVLN-3 or the Rheem RTG-70XLP-3, both rated at 7.0 GPM powered by substantial 160,000 BTUs, are designed for applications where showers, laundry, and dishwashers might be running concurrently. This output is a direct consequence of their high BTU input, enabling them to heat water rapidly enough to meet those simultaneous demands. In contrast, the Westinghouse Tankless Water Heater Electric 14kW 240V, with its stated maximum flow rate of 3.38 GPM, is clearly intended for lower-demand scenarios, perhaps a single sink or a small office restroom.

While its simplicity of installation might be appealing, failing to match its GPM capability to your site’s peak usage creates a bottleneck that no amount of precise temperature control, as seen on the Rheem electric models, can rectify.

The Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane and its sibling, the NEW Rinnai RX199iN Condensing Smart Sense, exemplify this need for careful BTU/GPM alignment. Their condensing technology offers efficiency advantages, but their core function is delivering hot water at a specific flow rate under pressure. When selecting between these, or even comparing them to the Rinnai CU160iN Commercial Natural Gas Condensing Tankless Water Heater, you must first identify your peak GPM requirement.

The RTGH Series 8.4 GPM 157,000 BTU model from Rheem RRTGH84DVLN3701171 explicitly states its flow performance, a key advantage for informed buyers, but it’s the BTU count that ultimately powers that flow.

Ultimately, the decision between a gas model like the Rheem RTG-70XLN-3 and an electric option like the Rheem RTEX-13 hinges on understanding what flow rate you need versus what you’re getting. The substantial BTU output of gas heaters allows for higher GPM at steeper temperature rises, which is critical for busier commercial settings or larger homes. For applications demanding consistent, high-volume hot water delivery, the Rheem RTGH Series 8.4 GPM 157,000 BTU is a superior choice for high-demand environments.

What to Look for in a Best Commercial Tankless Water Heater

Gas vs electric power source

When selecting your commercial tankless water heater’s power source, prioritize energy efficiency ratings. Gas models typically offer higher flow rates for simultaneous demands, and look for an Energy Factor of 0.8 or higher. Electric units are simpler to vent, often requiring no external venting, and are best for locations with limited gas supply.

Electronic ignition is universally superior to older pilot light systems, ensuring instant heating and eliminating wasted energy. For most commercial applications with consistent high demand, a high-efficiency gas model is the definitive choice for lower long-term operating costs and robust performance.

Flow rate and gpm needs

To meet your hot water demands, focus on the Gallons Per Minute (GPM) rating. A busy restaurant kitchen or a multi-stall restroom requires a higher GPM than a small office with a single sink. Calculate your peak simultaneous fixture usage by summing their GPM requirements.

For example, if three showers could run at once at 2.5 GPM each, you need at least a 7.5 GPM unit, with a buffer for safety. Choose models offering precise digital displays for accurate temperature setting, and ensure the unit has a wide adjustable temperature range, typically up to 140°F, to meet sanitation needs.

Compatibility with a recirculation pump ensures hot water is delivered instantly to distant fixtures. For anti-legionella protection, select units with automatic high-temperature flush cycles.

Temperature control and stability

For optimal user comfort and operational efficiency, ensure your commercial tankless water heater offers precise digital temperature control. Look for a unit with a clearly displayed digital thermostat that allows for micro-adjustments within a broad range, typically from 85°F to 140°F. This granular control prevents overheating and ensures consistent hot water delivery, crucial for sanitation and employee comfort.

Furthermore, confirm the unit’s compatibility with a hot water recirculation system; this feature is essential for minimizing water waste and providing near-instant hot water at the tap. Select models that integrate automatic anti-legionella features, such as high-temperature sanitization cycles, for enhanced health and safety.

Which Should You Choose?

• If you need a unit that can be installed indoors or outdoors regardless of fuel type, choose a model with advanced gas control systems and versatile venting.
• If you’re looking for an electric option with precise temperature control, choose a unit with external digital thermostatic control and durable copper heating elements.
• If your primary need is high-efficiency hot water for multiple bathrooms and appliances, choose a natural gas or propane unit with a high GPM (gallons per minute) output and substantial BTU input.
• If you require a compact, energy-saving unit designed for commercial spaces with flexible venting options, choose a condensing tankless water heater.

Quick Best Commercial Tankless Water Heater Buying Checklist

• Check GPM Needs: Calculate your peak hot water demand by counting simultaneous fixtures.
• Power Source Decision: Evaluate gas vs. electric based on installation, efficiency, and existing infrastructure.
• Ventilation Requirements: Ensure proper venting is possible for gas models, adhering to codes.
• Digital Temperature Control: Look for precise and easy-to-adjust temperature settings for consistent results.
• Compact Design: Consider space-saving wall-mounted units that free up valuable floor space.
• Recirculation Pump Compatibility: If faster hot water delivery is critical, ensure the unit supports a recirculation pump.

Frequently Asked Questions

What Is The Primary Benefit Of A Commercial Tankless Water Heater?

Commercial tankless water heaters offer a continuous supply of hot water on demand, preventing the depletion issues common with tank models. This means businesses can always meet their hot water needs without interruption.

How Does Gpm Affect Commercial Tankless Water Heater Selection?

GPM, or gallons per minute, is crucial as it dictates how much hot water the unit can produce simultaneously. Matching GPM to your business’s peak demand ensures enough hot water for all fixtures without fluctuating temperatures.

What’S The Difference Between Gas And Electric Tankless Water Heaters?

Gas models heat water instantly using natural gas or propane, generally offering higher GPM, while electric models use heating elements and are often simpler to install but may have lower GPM limits.

Are Commercial Tankless Water Heaters Energy Efficient?

Yes, commercial tankless water heaters are highly energy efficient because they only heat water when it’s needed, eliminating standby energy losses associated with traditional tank heaters. This can lead to significant cost savings.

What Maintenance Do Commercial Tankless Water Heaters Require?

Regular maintenance typically involves descaling to prevent mineral buildup, especially in hard water areas, and checking ventilation systems for gas models. Annual or bi-annual professional inspections are recommended.

Final Words

Choosing the best commercial tankless water heater provides a reliable, on-demand hot water solution vital for any business, from restaurants to hotels. These efficient systems ensure continuous supply and reduce energy waste, offering long-term value. Investing in the right unit enhances operational capacity and boosts customer satisfaction.