The best commercial tankless water heater offers unparalleled energy efficiency and endless hot water for demanding business environments. Selecting the right unit ensures your operations, from restaurants to hotels, never run cold. With numerous options available, performance can vary significantly, and a misstep can lead to wasted energy, insufficient supply, and costly downtime.
Factors like flow rate, energy source (gas or electric), and venting requirements all play a crucial role in finding a unit that perfectly matches your usage and facility needs. Read on to explore our top 10 picks for 2026 and find the ideal solution to keep your business running smoothly and efficiently.
For the best commercial tankless water heater, consider models like the Rinnai CX199iN Condensing Smart Sense or the Rinnai CU160iN Commercial Natural Gas Condensing Tankless Water Heater, which offer flexibility with indoor/outdoor installation and dual-fuel capabilities. These units are notable for their energy efficiency and space-saving design, heating water only when needed.
Best Commercial Tankless Water Heater Picks
| Image | Product | Buy |
|---|---|---|
Best Pick 1  | Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Commercial installs | Check Price |
Best Pick 2  | NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Smart homes | Check Price |
Best Pick 3  | Rheem 18kW 240V Tankless Electric Water Heater, Gray Best for: Electric option | Check Price |
Best Pick 4  | Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY Best for: Residential homes | Check Price |
Best Pick 5  | Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Best for: Indoor natural gas | Check Price |
How We Picked
We prioritized robust build quality and real-world performance when selecting the best commercial tankless water heater contenders. Safety and durability were paramount. Products with proven longevity and advanced features like self-modulation and versatile venting options, such as the Rinnai CX199iN and Rheem RTGH series, stood out.
We ruled out models lacking clear indication of commercial-grade components or those with limited flow rates unsuitable for high-demand environments. Focus remained on units offering exceptional value and reliable on-demand heating for 2026 operations.
What Most Buyers Get Wrong
Gas vs. Electric: BTU & kW Power Demands
When choosing a commercial tankless water heater, understand the fuel source’s impact on heating power. Gas units (like the Rinnai CX199iN or Rheem RTG-70DVLN-3/RTG-70XLP-3) are measured in BTUs, indicating their heating capacity per hour. Higher BTUs mean more hot water output.
Electric models (like the Rheem 18kW or Westinghouse 14kW) use kilowatts (kW). The higher the kW rating, the more hot water it can produce.
Ensure your facility’s electrical or gas infrastructure can support the unit’s power requirements.
Flow Rate and GPM for Business Needs
Commercial settings have higher hot water demands than residential ones. Look for the Gallons Per Minute (GPM) rating, which dictates how much hot water the unit can deliver simultaneously. A unit like the Rheem RTGH Series (8.4 GPM) or the Rheem RTG-70DVLN-3 (7.0 GPM) is suitable for multiple simultaneous uses in a business.
Consider the peak demand times in your establishment to select a GPM that avoids cold water sandwich scenarios, ensuring consistent hot water for all applications.
1. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: Versatile indoor/outdoor commercial installation.
With a 97% thermal efficiency rating, this Rinnai CX199iN model optimizes energy usage, directly reducing operational costs for your business. It’s designed to run on either natural gas or propane, allowing integration into existing fuel supply systems. Its 11.1 GPM flow rate ensures ample hot water for multiple fixtures simultaneously.
This condensing tankless water heater operates at 199,000 BTUs and boasts a maximum flow rate of 11.1 GPM, suitable for high-demand commercial applications. It features Smart Sense gas control for flexible fuel use and Versa Vent for indoor or outdoor installation, with a minimum activation flow rate of 0.5 GPM. Its stainless steel heat exchanger offers durability.
Pros
- 97% thermal efficiency reduces energy costs
- 11.1 GPM flow rate for heavy use
- Versa Vent allows indoor/outdoor installation
- Smart Sense gas control for fuel flexibility
Cons
- Requires an RX-OVC vent cap for outdoor installation.
Businesses needing versatile installation options and high efficiency will find this Rinnai model ideal. Its ability to run on gas or propane makes it adaptable to various commercial settings.
2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Compact design, high-flow for busy commercial spaces.
This Rinnai RX199iN tankless gas water heater measures the size of a small suitcase, maximizing space in commercial facilities. Its Smart Sense gas control system accommodates natural gas or propane, offering operational flexibility. The Versa Vent design facilitates placement in various indoor or outdoor commercial environments.
Delivering up to 11 GPM, this unit can supply hot water to approximately 7 fixtures concurrently, powered by 199,000 BTUs and boasting a UEF of .98. It operates on 120 volts with a wattage of 98 watts, ensuring efficient power consumption. The unit supports a maximum pressure of 150 PSI.
Pros
- Compact size saves commercial space
- 11 GPM flow rate serves multiple fixtures
- Smart Sense for gas or propane compatibility
- Versa Vent for indoor/outdoor installation
Cons
- Maximum temperature is limited to 140 degrees Fahrenheit.
Commercial establishments seeking a space-saving yet powerful hot water solution will benefit from this Rinnai model. Its adaptability to natural gas or propane suits various operational needs.
3. Rheem 18kW 240V Tankless Electric Water Heater, Gray
Best for: Powerful electric heating for high-demand commercial use.
With a 18kW power output, this Rheem electric tankless water heater delivers consistent hot water for commercial applications, eliminating the need for large storage tanks. Its durable copper immersion heating elements are field serviceable, ensuring long-term operational reliability. The unit’s self-modulation feature adjusts power to meet precise hot water demands.
This unit offers a flow rate of up to 4.4 GPM, ideal for small to medium commercial demands, powered by 18000 watts and 240 volts. It features an external digital thermostatic control with a 1-degree accuracy LED display for precise temperature management. Its 99.8% efficiency rating means minimal energy waste.
Pros
- 18kW power handles significant demand
- Up to 4.4 GPM flow rate
- Field-serviceable copper heating elements
- Precise digital temperature control
Cons
- Requires a 240V electrical connection, limiting installation location.
Businesses requiring a robust electric heating solution for consistent hot water will find this Rheem model effective. Its precise temperature control and field-serviceable elements are key advantages.
4. Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
Best for: Efficient electric heating for moderate commercial use.
Featuring a 13kW heating capacity, this Rheem RTEX-13 electric tankless water heater provides on-demand hot water for businesses with moderate demands. Its 99.8% energy efficiency rating minimizes operational costs. The unit’s external digital thermostatic control with LED display allows for easy temperature adjustment with 1-degree increments.
This unit offers a 4.8 GPM flow rate, suitable for multiple smaller applications or single higher-demand needs, operating at 13KW and 240 volts. Its self-modulating power control dynamically adjusts to hot water usage, preventing energy waste. The unit is designed for simple wall mounting and easy installation via included 1/2 NPT adapters.
Pros
- 13kW capacity for efficient heating
- 4.8 GPM flow rate serves multiple needs
- 99.8% energy efficiency saves costs
- Precise temperature control with LED display
Cons
- Requires a dedicated 240V circuit and adequate wiring, typical for electric high-wattage appliances.
Ideal for smaller commercial operations or specific stations needing reliable instant hot water, this Rheem heater offers cost-effective electric heating. Its user-friendly controls simplify operation.
5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: High-efficiency gas heating for 2-3 bathroom commercial spaces.
This Rheem RTG-70DVLN-3 natural gas water heater delivers up to 7.0 GPM, perfectly matching the hot water needs of 2–3 bathroom commercial spaces, ensuring simultaneous use for showers and laundry. Its 160,000 BTUs provide fast, reliable hot water during peak demand. Hot-start programming minimizes cold water bursts.
Operating on natural gas, this indoor unit features a maximum flow rate of 7.0 GPM and a heat output of 160,000 BTUs, validated by its high energy efficiency. It uses 120 volts and 132 watts for its integrated digital display and hot-start programming. The compact metal cabinet supports easy wall mounting.
Pros
- 7.0 GPM flow rate for multiple fixtures
- 160,000 BTUs ensure rapid heating
- High energy efficiency reduces gas costs
- Hot-start programming for consistent temperature
Cons
- Designed for indoor installation only, limiting placement options.
Perfect for businesses with consistent hot water needs across 2-3 bathrooms, this Rheem natural gas heater provides reliable performance. Its high efficiency and rapid heating suit busy commercial environments.
6. Westinghouse Tankless Water Heater Electric 14kW 240V, Instant On-Demand Hot
Best for: Space-saving electric heater with smart home compatibility.
This Westinghouse 14kW electric tankless water heater provides instant on-demand hot water, eliminating storage tank space requirements in commercial settings. Its 3.38 GPM maximum flow rate is suitable for various applications, and it is compatible with Google Assistant, Alexa, and Wi-Fi for modern management.
With a 14kW heating capacity at 240V, this unit delivers up to 3.38 GPM with a starting flow rate as low as 0.5 GPM, ensuring efficient operation. It requires one 60-amp double-pole circuit breaker and 6 AWG wire for installation. The unit is ETL Certified for safety and reliability.
Pros
- 14kW capacity for instant hot water
- 3.38 GPM flow rate efficiently used
- Smart home compatibility enhances control
- ETL Certified for safety assurance
Cons
- Requires a 60-amp circuit breaker and specific wiring, demanding professional installation.
Commercial users looking for an energy-efficient electric solution with modern smart home integration will appreciate this Westinghouse model. Its on-demand heating is ideal for tailored hot water needs.
7. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water
Best for: Outdoor propane heating for 2-3 bathroom commercial use.
This Rheem RTG-70XLP-3 liquid propane water heater is designed for outdoor installation, offering up to 7.0 GPM to supply hot water for 2–3 bathroom commercial spaces. Its 180,000 BTUs ensure swift and dependable hot water delivery, even during peak demand. Hot-start programming maintains consistent output.
Powered by liquid propane, this unit delivers 7.0 GPM with a heat output of 180,000 BTUs and features high efficiency. It uses 120 volts and 132 watts for its core functions and features like hot-start programming. The compact and lightweight design facilitates easy wall mounting in outdoor commercial areas, with 1/2 gas line compatibility.
Pros
- 7.0 GPM flow rate suitable for multiple fixtures
- 180,000 BTUs for rapid heating
- Outdoor installation ideal for limited indoor space
- Hot-start programming ensures consistent temperature
Cons
- Requires a liquid propane supply, which may not be available or preferred in all locations.
Businesses needing outdoor-capable propane heating for 2-3 bathroom setups will find this Rheem model a strong choice. Its robust design and high flow rate meet demanding commercial needs.
8. Rinnai CU160iN Commercial Natural Gas Condensing Tankless Water Heater, Indoor
Best for: Commercial-grade gas heating with Wi-Fi monitoring.
This Rinnai CU160iN commercial tankless water heater features a space-saving design that conserves energy by heating only when necessary, directly benefiting operational budgets. It provides a high-performance 9 GPM hot water flow rate, ensuring a powerful, constant stream for commercial needs. Circ-Logic technology enhances heating reliability.
This gas-powered unit operates at a robust 9 GPM flow rate, supported by advanced recirculation technology and Wi-Fi monitoring capabilities. While specific efficiency values are not provided, it’s designed for high performance in demanding commercial settings. It is wall-mounted and draws power via 120 volts.
Pros
- 9 GPM flow rate for high demand
- Energy-saving tankless design
- Wi-Fi monitoring for remote insights
- Circ-Logic for reliable heating performance
Cons
- Specific efficiency rating is not provided in the product details.
Commercial facilities requiring significant and consistent hot water, along with modern monitoring, will benefit from this Rinnai unit. Its high flow rate and smart features suit busy environments.
9. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: Outdoor natural gas for 2-3 bathroom commercial use.
The Rheem RTG-70XLN-3 outdoor tankless gas water heater provides up to 7.0 GPM, ideal for 2–3 bathroom commercial spaces needing consistent hot water for showers and laundry. Powered by natural gas with 160,000 BTUs, it guarantees fast, reliable hot water during peak demand periods. Its outdoor design optimizes space within buildings.
This unit offers a 7.0 GPM flow rate with 160,000 BTUs of heat output, featuring high efficiency and freeze protection. It operates on 120 volts and includes features like hot-start programming for consistent temperatures and a self-diagnostic program for maintenance. Its durable metal cabinet is designed for outdoor wall mounting.
Pros
- 7.0 GPM flow rate serves multiple fixtures
- 160,000 BTUs ensure quick heating
- Outdoor installation frees up indoor space
- Hot-start programming for consistent output
Cons
- Requires an outdoor installation location, which may be subject to weather conditions.
Businesses with 2-3 bathrooms that can accommodate an outdoor unit will find this Rheem natural gas heater highly effective. Its reliable performance suits demanding commercial hot water needs.
10. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120
Best for: High-flow natural gas for commercial applications.
This Rheem RTGH Series tankless water heater delivers a robust 8.4 GPM flow rate, capable of handling substantial commercial hot water demands from multiple fixtures simultaneously. With an output of 157,000 BTUs, it ensures rapid and continuous hot water supply. Its exclusive Hot Start Programming minimizes cold water issues.
Providing flow rates from 0.4 to 8.4 GPM, this unit operates at 120 volts and uses 132 watts with electric ignition for efficiency. It allows temperature settings between 100 to 140°F via its wall-mounted control. The heat exchanger is covered by a 15-year manufacturer warranty for long-term assurance.
Pros
- 8.4 GPM high flow rate
- Rapid 157,000 BTU heating output
- Hot Start Programming for consistency
- Durable heat exchanger with long warranty
Cons
- Limited to 140 degrees Fahrenheit maximum temperature setting.
Commercial establishments requiring a high-volume, reliable natural gas water heater will benefit from this Rheem RTGH model. Its substantial flow rate is ideal for demanding operational environments.
Gas vs. Electric: BTUs vs. Amps Define Tankless Choices
The fundamental divergence in selecting a best commercial tankless water heater boils down to BTUs for gas models and amperage for electric, directly dictating the unit’s capacity and installation complexity. For instance, units like the Rheem RTG-70DVLN-3, Rheem RTG-70XLP-3, Rheem RTG-70XLN-3, and Rheem RRTGH84DVLN3701171 all operate on natural gas or propane, pushing out a robust 160,000 BTUs or more to deliver a consistent 7.0 GPM or higher. This high BTU output means these gas units can capably handle multiple simultaneous hot water demands, making them ideal for businesses with high and frequent usage, like busy restaurants or large multi-unit residential buildings.
Their installation, while requiring gas lines and appropriate venting, avoids the substantial electrical infrastructure upgrades that electric tankless models often necessitate.
Contrarily, electric tankless heaters such as the Rheem 18kW 240V Tankless Electric Water Heater and the Westinghouse Tankless Water Heater Electric 14kW 240V, operate on 240V and draw significant amperage, with the Westinghouse specified at 59A and requiring a 60-amp circuit. While these units offer the advantage of simpler installation without gas lines or venting, their flow rate and heating capacity are directly tied to incoming electrical power. The Rheem 18kW unit, for example, offers excellent temperature accuracy with its +/1 degree accuracy and advanced self-modulation, but its 18kW rating translates to a maximum flow rate that may not keep pace with truly simultaneous, high-demand applications that a high-BTU gas unit can manage.
Buyers must meticulously calculate their peak demand in Gallons Per Minute (GPM) and temperature rise required, then match it to the unit’s capabilities, understanding that insufficient amperage will bottleneck an electric heater’s performance far more acutely than less-than-optimal gas pressure might an equivalent gas unit.
The Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane and the NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane, along with the Rinnai CU160iN Commercial Natural Gas Condensing Tankless Water Heater, exemplify advancements in the gas category, particularly with features like Versa Vent for indoor/outdoor installation flexibility and Smart Sense gas control. Their condensing technology, while adding to the initial cost and requiring a condensate drain, promises higher energy efficiency compared to non-condensing models like the base Rheem RTG series. However, the core decision point remains the fuel source.
If your facility already has robust natural gas lines and venting infrastructure, prioritizing high-BTU gas models from Rinnai or Rheem for raw, on-demand power is a pragmatic approach. If electrical upgrades are feasible and your usage profile is more moderate or spread out, a powerful electric unit like the Rheem 18kW can offer installation ease that outweighs its flow rate limitations for certain applications.
Ultimately, the perceived performance difference between these units is less about brand superiority and more about aligning the unit’s power delivery mechanism—BTUs for gas, amps for electric—with the facility’s actual, real-time hot water consumption patterns. For applications demanding consistent, high-volume output across multiple fixtures, the Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane stands out due to its powerful gas input and condensing efficiency, but only if the natural gas infrastructure is in place.
What to Consider for the Best Commercial Tankless Water Heater
Flow rate capabilities
Consider your peak demand in Gallons Per Minute (GPM). A small office or retail space typically needs 3-5 GPM, while a busy restaurant or hotel may require 10 GPM or more. Look for units with an activation flow rate of 0.5 GPM or lower to ensure hot water is delivered even with low usage.
For maximum simultaneous use, choose a heater with a GPM rating that comfortably exceeds your highest expected simultaneous draw. Select a high-GPM unit for demanding, high-volume applications.
Energy efficiency ratings
Prioritize a high Energy Factor (EF) for optimal long-term savings. Ratings above 0.90 are excellent, indicating minimal energy waste. Electric models typically offer higher EF ratings than gas, but gas models often have lower upfront operating costs.
Minimize standby heat loss by choosing a tankless unit, as they only heat water on demand. For the most energy-conscious operation, opt for a high-EF electric tankless water heater.
Temperature control precision
Precise temperature control is crucial for commercial comfort and safety. Digital thermostats offer exact degree adjustments, essential for applications like medical facilities or salons. Ensure the unit’s temperature rise capability matches your coldest incoming water temperature to achieve your desired output temperature, especially in colder climates.
Units with built-in thermostats that support recirculation loops will ensure immediate hot water at fixtures. Choose digital controls for the most accurate and consistent hot water delivery.
Ventilation and installation requirements
Assess your facility’s venting and utility infrastructure. Direct-vent units are versatile, drawing fresh air from outside and expelling exhaust, ideal for indoor installation. Power-vent units use a fan for exhaust and can be vented horizontally or vertically.
Natural-vent units require a vertical chimney. Confirm adequate gas line size and electrical service for your chosen unit.
For ease of installation in tight spaces, a compact direct-vent model is often the best choice.
Which Should You Choose?
- If your installation location is flexible and you need to use either natural gas or propane, choose a model with a versatile gas control system and indoor/outdoor venting capabilities.
- If you have limited space and need to conserve energy, opt for a condensing unit that heats water only when needed and offers multiple venting options.
- If electricity is your primary energy source and precise temperature control is crucial, look for an electric tankless heater with an external digital thermostatic control and self-modulating power.
- If you require a high flow rate for multiple simultaneous hot water uses, select a natural gas or propane model that delivers 7.0 GPM or more.
Quick Best Commercial Tankless Water Heater Buying Checklist
- Assess Peak Demand: Determine the maximum gallons per minute (GPM) your business needs simultaneously.
- Verify Certifications: Ensure the unit meets relevant commercial safety and performance standards.
- Consider Energy Source: Evaluate whether natural gas, propane, or electric best suits your facility’s infrastructure and costs.
- Check Venting Options: Confirm the available venting methods (direct, natural, power) are compatible with your installation space.
- Measure Available Space: Accurately gauge the physical dimensions for installation, accounting for service access.
- Review Manufacturer Warranty: Understand the coverage duration and terms for commercial applications.
Frequently Asked Questions
What Is The Primary Advantage Of Commercial Tankless Water Heaters?
Commercial tankless water heaters offer an endless supply of hot water, unlike traditional tank models. This continuous availability is crucial for businesses with high or fluctuating demand, preventing shortages during peak usage periods.
How Do I Determine The Correct Flow Rate For My Business?
To find the right flow rate, sum the GPM of all hot water fixtures that might operate concurrently. Consider the busiest times of day and the specific demands of your equipment.
Are Commercial Tankless Water Heaters More Energy-Efficient?
Yes, commercial tankless units are generally more energy-efficient because they only heat water on demand, eliminating standby heat loss. This leads to significant cost savings on energy bills over time.
What Types Of Venting Are Common For Commercial Tankless Heaters?
Common venting types include direct vent (requiring dedicated intake and exhaust), natural vent (using existing chimney), and power vent (using a fan). The best option depends on your building’s layout and local codes.
Can A Commercial Tankless Water Heater Handle Multiple Simultaneous Uses?
Yes, commercial-grade tankless units are designed for high demand and can usually manage multiple simultaneous hot water needs. Selecting a model with a sufficient GPM rating ensures you can run several fixtures at once without issue.
Final Words
Investing in the best commercial tankless water heater provides unparalleled efficiency and a continuous hot water supply for your business operations. These advanced systems deliver significant energy savings and are built to meet rigorous commercial demands. Make the switch to a reliable and cost-effective hot water solution today.