The best commercial tankless water heater delivers on-demand hot water and significant energy savings for businesses requiring high volume. Businesses like restaurants, hotels, and large facilities need robust solutions to ensure uninterrupted hot water, making the selection of the right model critical. Factors like flow rate, fuel type (gas or electric), and warranty vary greatly, and choosing a unit that doesn’t match your specific needs can lead to premature failure, inadequate hot water delivery, and wasted operational expenses.
Performance and longevity are key considerations. To help you make an informed decision, we’ve compiled a list of the top commercial tankless water heaters on the market in 2026, focusing on those that offer superior efficiency and durability for demanding commercial applications.
The best commercial tankless water heater often prioritizes consistent performance and versatile installation, with models like the Rinnai CX199iN Condensing Smart Sense offering indoor/outdoor flexibility and Smart Sense gas control for propane or natural gas use. For electric options, the Rheem 18kW 240V Tankless Electric Water Heater stands out with its external digital thermostatic control and self-modulating power for varying demand.
Best Commercial Tankless Water Heater: At a Glance
| Image | Product | Buy |
|---|---|---|
Best Pick 1  | Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Commercial spaces | Check Price |
Best Pick 2  | NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: High-demand settings | Check Price |
Best Pick 3  | Rheem 18kW 240V Tankless Electric Water Heater, Gray Best for: Electric efficiency | Check Price |
Best Pick 4  | Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY Best for: Residential use | Check Price |
Best Pick 5  | Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Best for: Standard gas | Check Price |
How We Picked
We prioritized build quality and durability, focusing on models with robust construction and high-efficiency ratings. Real-world performance, particularly hot water delivery rates and precise temperature control, was paramount for identifying the best commercial tankless water heater. We also considered safety features and innovative technologies like Wi-Fi connectivity and self-modulation.
Models lacking sufficient detail or proven performance were ruled out. Our selection process ensured each of the chosen heaters offers exceptional value and long-term reliability, capable of meeting demanding commercial needs through 2026.
What Most Buyers Get Wrong
Commercial Water Heater Sizing: GPM vs. BTU
When selecting a commercial tankless water heater, understanding flow rate (GPM) and heating capacity (BTU) is critical. While models like the Rheem RTG-70DVLN-3 and RTG-70XLP-3 offer up to 7.0 GPM, they are often geared towards larger homes. For true commercial applications, consider what your business’s peak demand is.
High-demand settings might require units with higher BTU inputs, such as the Rheem RTGH Series at 157,000 BTU, to ensure simultaneous hot water availability for multiple fixtures.
Condensing vs. Non-Condensing Technology
The choice between condensing and non-condensing technology significantly impacts energy efficiency and installation. Condensing units, like the Rinnai CX199iN and CU160iN, recapture exhaust heat, leading to higher energy savings over time. However, they require specific venting materials and may involve a condensate drain.
Non-condensing models, such as the Rheem RTG-70DVLN-3 or RTG-70XLN-3, are generally simpler to install, but less energy-efficient. Assess your operational budget and installation environment when deciding.
1. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: High-efficiency indoor/outdoor flexibility.
With 97% thermal efficiency, this Rinnai CX199iN model optimizes energy use, leading to reduced operational costs for your business. It can be installed indoors or outdoors, and runs on either natural gas or propane, offering significant installation flexibility.
Boasting a 199,000 BTU output and a 11.1 GPM flow rate, this unit provides ample hot water for commercial needs. Its Smart Sense gas control system and Versa Vent technology ensure reliable performance and adaptability to various installation environments.
Pros
- 97% thermal efficiency reduces energy costs
- 11.1 GPM flow rate handles multiple fixtures
- Indoor or outdoor installation flexibility
- Smart Sense gas control for propane/natural gas
Cons
- Requires an RX-OVC vent cap for outdoor installations.
Installers needing a versatile, high-efficiency unit for either natural gas or propane will find this Rinnai a cost-effective solution. Its ability to perform indoors or outdoors simplifies site-specific setup requirements.
2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Compact, high-flow gas unit.
This Rinnai RX199iN unit, measuring just the size of a small suitcase, delivers up to 11 GPM, allowing up to 7 fixtures to run simultaneously. Its Smart Sense gas control system automatically adjusts to natural gas or propane.
The 199,000 BTU heat output and a 11 GPM flow rate ensure consistent hot water supply for busy commercial settings. Its compact dimensions and Versa Vent technology contribute to its flexible indoor or outdoor installation capabilities.
Pros
- 11 GPM flow rate serves multiple fixtures
- Compact suitcase-sized design
- Smart Sense gas control for fuel flexibility
- Versa Vent for indoor/outdoor installation
Cons
- Maximum temperature is capped at 140°F.
Businesses requiring a compact yet powerful gas water heater that can handle simultaneous demands will benefit from this Rinnai. Its size makes it ideal for locations with limited installation space.
3. Rheem 18kW 240V Tankless Electric Water Heater, Gray
Best for: Powerful 18kW electric heating.
Producing up to 4.4 GPM, this Rheem 18kW electric water heater features durable copper heating elements designed for field serviceability. Its precise temperature control adjusts within a 1°F accuracy for consistent output.
With an 18kW wattage and 99.8% efficiency, this unit delivers reliable hot water on demand. The external digital LED display simplifies temperature adjustments, and the 3/4 inch NPT water connections facilitate straightforward installation.
Pros
- 4.4 GPM flow rate for consistent hot water
- Durable copper heating elements
- Precise +/- 1°F temperature accuracy
- 99.8% energy efficiency
Cons
- Requires dedicated 240V electrical service and has a maximum temperature of 140°F.
This Rheem 18kW electric model is suited for commercial applications where consistent, precise temperature is critical and electric power is available. Its self-modulating design ensures power is used only as needed.
4. Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
Best for: Compact 13kW electric heater.
This Rheem RTEX-13 tankless electric water heater provides up to 4.8 GPM with its 13kW heating capacity, ensuring on-demand hot water. It features an adjustable digital thermostatic control with a 1°F increment setting.
The unit boasts 4.8 GPM flow rate at its rated capacity and 99.8% energy efficiency, minimizing waste. The inclusion of 1/2 inch NPT adapters and side compression water connections simplifies the installation process.
Pros
- 4.8 GPM flow rate for immediate hot water
- 99.8% energy efficiency
- Adjustable digital temperature control
- Simple installation with included adapters
Cons
- Has a maximum temperature output of 140°F and requires a dedicated 240V circuit.
A good option for smaller commercial spaces or auxiliary water heating needs requiring electric power, this Rheem RTEX-13 ensures hot water availability. Its user-friendly controls and efficient operation make it a practical choice.
5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: Indoor natural gas with hot start.
Delivering up to 7.0 GPM, this Rheem RTG-70DVLN-3 high-efficiency unit is powered by natural gas with 160,000 BTUs for rapid hot water. Its indoor design features a durable metal cabinet and wall-mounting support.
The 7.0 GPM flow rate supports 2-3 bathrooms simultaneously, ideal for busy households or small businesses. Hot-start programming minimizes cold water bursts, ensuring a consistent temperature from the first use.
Pros
- 7.0 GPM flow rate handles multiple fixtures
- 160,000 BTU natural gas power
- Hot-start programming for consistent temps
- Designed for indoor installation
Cons
- Requires 1/2 inch gas line and is not smart home compatible.
Commercial businesses or multi-unit residences needing reliable natural gas hot water will find this Rheem RTG-70DVLN-3 suitable. Its high flow rate and integrated display provide efficient and convenient operation.
6. Westinghouse Tankless Water Heater Electric 14kW 240V, Instant On-Demand Hot
Best for: Wi-Fi enabled 14kW electric.
This Westinghouse 14kW electric tankless water heater provides instant on-demand hot water with a 3.38 GPM maximum flow rate. It leverages smart home compatibility, working with Google Assistant and Alexa.
With a heating output of 14,000 watts and a 3.38 GPM flow rate, this unit is efficient for smaller commercial demands. It requires one 60-amp double-pole circuit breaker and a 6 AWG wire for installation.
Pros
- 3.38 GPM maximum flow rate
- Smart home compatible (Google Assistant, Alexa)
- Instant on-demand hot water
- ETL Certified
Cons
- Requires a powerful 60-amp circuit and 6 AWG wiring for installation.
Businesses seeking an electric, on-demand water heating solution with smart home integration will appreciate this Westinghouse model. Its Wi-Fi capabilities offer convenient control and monitoring.
7. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water
Best for: Outdoor liquid propane unit.
This Rheem RTG-70XLP-3 outdoor tankless water heater runs on liquid propane, delivering up to 7.0 GPM for consistent hot water needs. Its durable metal cabinet is designed for exterior installation.
Fueled by 180,000 BTUs from liquid propane, this unit supports 2-3 bathrooms simultaneously with its 7.0 GPM flow rate. The compact and lightweight design simplifies wall mounting by a qualified installer.
Pros
- 7.0 GPM flow rate for multi-fixture use
- Outdoor installation design
- Liquid propane fuel source
- Compact and lightweight
Cons
- Requires 1/2-inch gas line compatibility and is not smart home compatible.
Ideal for outdoor commercial installations requiring a robust liquid propane water heater, this Rheem RTG-70XLP-3 provides high flow rates. Its design is optimized for external mounting and weather resistance.
8. Rinnai CU160iN Commercial Natural Gas Condensing Tankless Water Heater, Indoor
Best for: Commercial-grade gas with recirculation.
Garnering a 9 GPM hot water flow rate, this Rinnai CU160iN commercial unit is powered by natural gas and features recirculation technology for rapid hot water delivery. Its space-saving design conserves energy by heating only when required.
The 9 GPM flow rate is suitable for demanding commercial applications, ensuring a powerful and constant stream. Wi-Fi monitoring capabilities allow for remote management and performance tracking.
Pros
- 9 GPM flow rate for high demand
- Recirculation Technology for fast hot water
- Wi-Fi Monitoring included
- Energy-saving on-demand heating
Cons
- Specific efficiency rating not provided in technical details.
Commercial businesses operating with high hot water demands will benefit from this Rinnai CU160iN’s robust flow rate and recirculation features. Its Wi-Fi monitoring adds a layer of operational control.
9. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: Outdoor natural gas with freeze protection.
This Rheem RTG-70XLN-3 outdoor tankless natural gas water heater offers a 7.0 GPM flow rate, perfect for businesses with multiple hot water demands. It includes freeze protection for year-round operation.
Powered by 160,000 BTUs of natural gas, this unit ensures fast, reliable hot water, even during peak usage. Its outdoor design features a durable metal cabinet and easy wall mounting.
Pros
- 7.0 GPM flow rate for substantial use
- Outdoor installation ready
- Natural gas powered
- Freeze protection included
Cons
- Maximum temperature is limited to 140°F.
For commercial properties requiring outdoor natural gas water heating, this Rheem RTG-70XLN-3 unit is a reliable choice. Its flow rate and built-in features like freeze protection ensure consistent performance.
10. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120
Best for: High-flow gas with hot start programming.
With a flow rate range of 0.4 to 8.4 GPM, this Rheem RTGH Series unit utilizes 157,000 BTUs for dynamic hot water delivery. Its exclusive Hot Start Programming minimizes cold water gaps for consistent temperature.
This unit provides up to 8.4 GPM, suitable for high-demand commercial settings. The default temperature setting is 120°F, with adjustable settings from 100°F to 140°F, managed by an electric ignition system.
Pros
- 8.4 GPM maximum flow rate
- Exclusive Hot Start Programming
- Adjustable temperature settings
- Electric ignition
Cons
- Requires dedicated gas line and is not smart home compatible.
Businesses needing a high-flow, natural gas water heater with advanced features will find this Rheem RTGH Series unit effective. Its efficient operation and temperature consistency make it well-suited for commercial use.
Gas vs. Electric BTU Output vs. Kilowatts
When selecting a best commercial tankless water heater, the ultimate deciding factor isn’t the brand or even the feature set; it’s the fundamental energy source and its inherent capacity for heat delivery over time. This principle is starkly illustrated by the gulf between high-BTU gas units and their kilowatt-rated electric counterparts, a difference that translates directly to operational capability and, ultimately, user satisfaction.
Gas models, exemplified by the Rheem RTG-70DVLN-3 and its propane variant, the Rheem RTG-70XLP-3, boast significant BTU outputs (160,000 BTUs in these cases) and flow rates of up to 7.0 GPM, making them robust choices for simultaneous demands like showers and laundry. Similarly, the Rheem RTG-70XLN-3 offers the same high performance on natural gas. These units excel at rapidly restoring temperature to incoming water, ensuring consistent hot water even under heavy load.
The Rinnai CX199iN Condensing Smart Sense Commercial and the NEW Rinnai RX199iN Condensing Smart Sense, also gas and propane configurable, highlight versatility with their indoor/outdoor installation and Smart Sense gas control, but their core strength remains significant thermal capacity.
Electric units, however, operate on a fundamentally different scale. The Rheem 18kW 240V Tankless Electric Water Heater, for instance, delivers its power in kilowatts, a metric that, while substantial for its type, has a more limited GPM output compared to equivalent gas units. The Westinghouse Tankless Water Heater Electric 14kW 240V, with a maximum flow rate of 3.38 GPM, is clearly designed for lighter duty or less simultaneous demand.
While models like the Rheem 240V Heating Chamber RTEX-13 and the Rheem RRTGH84DVLN3701171 offer adjustable temperatures and self-modulation, their electric heating elements, even with durable copper construction, inherently have a lower peak water heating capacity per GPM than a high-BTU gas burner. This isn’t a flaw in design, but a physical limitation based on how electricity is converted to heat versus how gas combustion works.
The Rinnai CU160iN Commercial Natural Gas Condensing Tankless Water Heater provides a compelling example of gas efficiency, but its performance metrics still align with its energy source. Trying to achieve the same flow rates and temperature rise with electric power would necessitate significantly higher amperage draws and potentially multiple circuits, as evidenced by the Westinghouse model’s 59A requirement and single 60-amp circuit. The mistake is assuming that an electric unit of comparable kilowatt rating will perform identically to a gas unit with a similar BTU rating; they are not interchangeable metrics for flow rate and temperature output in practical terms.
For applications demanding consistent, high-volume hot water delivery across multiple fixtures or appliances simultaneously, the Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane offers the superior raw heating power needed.
What to Look For in a Commercial Tankless Water Heater
Gas vs electric powering
When powering your commercial tankless water heater, choose natural gas for its higher input capabilities and cost-effectiveness in most areas, demanding at least 150,000 BTU/hr for robust performance on peak demand days. Electric units require significant electrical infrastructure, often needing dedicated 240V circuits with 60-80 amps per element, making them suitable for smaller loads or where gas isn’t feasible. Prioritize units with energy efficiency ratings above 95%; pilotless ignition systems are standard and vastly more efficient than older standing pilot models.
For maximum operational economy and capacity, select a natural gas model with a pilotless ignition.
Flow rate and gpm
The critical factor for simultaneous demand is the gallons per minute (GPM) your system can deliver. Aim for a minimum of 8 GPM at a 120°F output temperature for applications with multiple simultaneous fixtures. Consider the temperature rise – a 90°F rise means heating water from 50°F to 140°F, so verify the GPM rating at your specific incoming water temperature.
Ensure your existing water pressure meets the heater’s minimum requirement, typically around 15 PSI. Select a unit certified for the highest GPM at your required temperature rise to confidently serve all concurrent usage points.
Space and venting requirements
Space for mounting and adequate venting are paramount. Look for compact units, often under 30 inches in height and width, that can be wall-mounted to conserve floor space. Venting clearance requirements are strict; ensure at least 12 inches of radial clearance and confirm the heater is compatible with either single-wall stainless steel or Category III/IV venting materials suitable for your chosen path, whether horizontal through a wall or vertical through the roof.
For utmost installation flexibility and to save interior space, opt for an outdoor-rated model with a corrosion-resistant stainless steel vent.
Temperature control and features
Precise temperature control is essential for customer satisfaction and safety. A digital display with 1°F increment accuracy allows perfect setting of output temperatures, crucial for diverse applications. Programmable setpoints are invaluable for adjusting to different times of day or occupancy levels, optimizing energy use.
Robust freeze protection, usually integrated fan and element safeguards, prevents damage in colder climates. For advanced management and remote monitoring, smart connectivity features are a significant benefit.
Choose a heater with a clear digital display and programmable setpoints for consistent, efficient hot water delivery.
Which Should You Choose?
- If you need flexibility for indoor or outdoor installation and have both natural gas or propane options available, choose a condensing model with smart gas control.
- If you have limited space and prioritize energy efficiency for commercial use, choose an indoor condensing unit with multiple venting options.
- If precise temperature control is crucial and you prefer electric power, choose a model with external digital thermostatic control and copper heating elements.
- If you need to supply hot water for 2-3 bathrooms with multiple simultaneous uses, choose a non-condensing gas unit capable of at least 7.0 GPM.
Quick Best Commercial Tankless Water Heater Buying Checklist
- Confirm Gas Type: Ensure the heater is compatible with your available natural gas or propane supply.
- Check GPM Needs: Calculate the maximum gallons per minute (GPM) required for peak demand to prevent cold water interruptions.
- Evaluate Energy Source: Decide between the long-term cost-effectiveness of natural gas or the convenience of electric models.
- Assess Venting: Verify that installation meets manufacturer and local code requirements for safe ventilation.
- Consider Space: Measure available space for the unit and confirm mounting orientation compatibility.
- Review Controls: Look for user-friendly digital interfaces and precise temperature adjustments for optimal performance.
Frequently Asked Questions
What Is The Primary Advantage Of Commercial Tankless Water Heaters?
Commercial tankless water heaters offer continuous hot water on demand, unlike traditional tank heaters that deplete their supply. This means businesses can avoid running out of hot water during peak usage, ensuring consistent service for customers and operations.
How Do Gas Commercial Tankless Water Heaters Differ From Electric Models?
Gas commercial tankless water heaters typically provide higher flow rates for demanding applications but require gas line installation and proper ventilation. Electric models are often easier to install and more compact but may have limitations on simultaneous hot water use.
What Flow Rate Is Typically Needed For Commercial Applications?
Commercial applications often require higher flow rates, typically ranging from 5 to 20 gallons per minute (GPM) or more, depending on the business type and number of fixtures. This ensures sufficient hot water supply for multiple simultaneous uses without interruption.
Are Commercial Tankless Water Heaters Energy-Efficient?
Yes, commercial tankless water heaters are generally more energy-efficient as they only heat water when needed, eliminating standby energy losses associated with storage tanks. This can lead to significant operational cost savings over time.
What Are Essential Installation Considerations For These Units?
Proper installation is crucial and includes ensuring adequate gas supply or electrical capacity, correct venting according to local codes, and sufficient water pressure for optimal operation. Professional installation is highly recommended to ensure safety and performance.
Final Words
Investing in the best commercial tankless water heater provides businesses with reliable, on-demand hot water and significant energy savings. Their efficiency and continuous supply capabilities are invaluable for maintaining smooth operations and customer satisfaction. Upgrading to a tankless system is a smart move for enhanced performance and reduced utility costs.