Choosing the right hot water system for an apartment building is about more than raw flow rate. You need dependable performance, the right fuel type, and a unit sized for real-world peak demand.
This roundup of commercial tankless water heaters for apartment buildings focuses on practical options that balance efficiency, installation flexibility, and long-term operating cost.
Best 10 Commercial Tankless Water Heaters for Apartment Buildings Picks for 2026
Commercial Indoor/Outdoor Gas Pick
- 11.1 GPM supports up to 7 fixtures
- Indoor or outdoor install with Versa Vent
- Works with natural gas or propane
Best For: Apartment properties needing flexible gas installation and high hot-water output.
Outdoor High-Capacity Smart Pick
APUS 190,000 BTU 8.1 GPM Natural Gas Unit
- 8.1 GPM capacity supports multiple fixtures
- WiFi and wired controls for temperature management
- Outdoor design with freeze and wind protection
Best For: Apartment buildings needing an outdoor, space-saving hot water solution
Compact Point-of-Use Electric Option
- Compact electric design for point-of-use use
- Self-modulating system for steadier output
- ETL certified with multiple safety protections
Best For: Small apartment or utility areas needing local hot water
Indoor High-Output WiFi Pick
Mizudo 199,000 BTU 10.3 GPM Indoor Unit
- 10.3 GPM supports higher simultaneous demand
- WiFi control with scheduling and alerts
- Sealed direct vent indoor combustion design
Best For: Larger apartment buildings needing high-flow indoor hot water
Heavy-Duty Multi-Point Pick
27kW NOVIEEX Whole-House Electric Heater
- Up to 7.4 GPM for 3-4 points of use
- 77°F to 140°F control in 1°F steps
- Requires major electrical capacity and pro install
Best For: Large apartments or shared units with strong electrical service
Smart Flow-Control Pick
27kW WINTEMP WiFi Tankless Heater
- Auto flow control stabilizes outlet temperature
- WiFi app tracks flow and usage
- Up to 6.5 GPM with compact wall-mount design
Best For: Small apartment setups that value smart monitoring and steady temperature
Commercial Indoor/Outdoor Gas Pick – Rinnai CX199iN 199k BTU
For commercial tankless water heaters for apartment buildings, the Rinnai CX199iN is a strong fit when you want compact size, high output, and flexible gas options. It delivers up to 11.1 GPM and supports natural gas or propane, with indoor or outdoor installation possible using the Versa Vent system.
Best For: Apartment properties needing a compact, high-output gas unit with installation flexibility.
Pros:
- Up to 11.1 GPM, enough for as many as 7 fixtures at once
- Indoor or outdoor install support with Versa Vent
- Smart Sense gas control works with natural gas or propane
- UEF .98 and Smart-Circ recirculation for efficient operation
Cons:
- Professional installation is recommended
- Outdoor installation requires the RX-OVC vent cap
- WiFi control needs the separate Controlr module
This unit stands out if you need commercial-ready output in a space-saving package, but it still depends on proper venting and professional setup. The built-in recirculation and strong warranty terms make it a practical long-term pick for multi-unit hot water demand.
High-Efficiency Electric Option – Rheem RTEX-24 24kW
In commercial tankless water heaters for apartment buildings, the Rheem RTEX-24 makes sense where electric service is available and venting is a concern. It offers continuous hot water, a compact wall-mount design, and 99.8% energy efficiency, but it does require substantial electrical capacity.
Best For: Buildings with the electrical infrastructure to support a ventless electric tankless unit.
Pros:
- Continuous hot water for whole-home style demand
- No venting required
- Adjustable digital temperature display in 1-degree increments
- Compact wall-mounted design saves space
Cons:
- Requires three 40 AMP double-pole breakers
- 200 AMP household service is recommended
- Performance depends on ground water temperature and location
This is a practical electric choice when you can accommodate the power draw and want a simpler installation path. It is best viewed as an infrastructure-dependent option rather than a universal fit for every apartment building.
Flexible Premium Gas Choice – Rinnai RX199iN Smart Sense
Among commercial tankless water heaters for apartment buildings, the Rinnai RX199iN is a versatile premium option with the same high-output class and indoor/outdoor flexibility as the CX model. It delivers up to 11.1 GPM, supports natural gas or propane, and uses a Smart Sense gas control system for adaptable installation planning.
Best For: Apartment buildings that want a flexible, high-efficiency gas unit with premium installation versatility.
Pros:
- Up to 11.1 GPM for demanding multi-fixture use
- Indoor or outdoor installation support
- Smart Sense gas control accepts natural gas or propane
- UEF .98 and Quick Flush feature support efficient upkeep
Cons:
- Professional installation is recommended
- Outdoor installation requires the RX-OVC vent cap
- WiFi control requires the separate Controlr module
If your building needs flexibility without giving up output, this model is easy to place near the top of the list. Its efficiency, compact footprint, and long warranty make it a strong long-term commercial-style solution.
Budget Electric Pick – Rheem RTEX-13 13kW
For commercial tankless water heaters for apartment buildings, the Rheem RTEX-13 is a smaller electric option suited to lighter demand areas. It offers digital temperature control, a compact wall-mounted design, and very high stated efficiency, but its output is far below the larger 24kW model.
Best For: Smaller apartments or point-of-use applications with modest hot-water needs.
Pros:
- Compact wall-mounted design
- External digital thermostatic control with LED display
- 99.8% energy efficient
- Simple installation with included 1/2 NPT adapters
Cons:
- Lower output than larger commercial-style units
- Electric demand may limit where it can be used
- Best for modest flow needs rather than full-building demand
This model can work well where space and simplicity matter more than maximum volume. For apartment buildings, it fits best as a smaller-scale solution rather than a central hot-water workhorse.
Outdoor High-Capacity Smart Pick – APUS 190,000 BTU 8.1 GPM Natural Gas Unit
If you’re comparing commercial tankless water heaters for apartment buildings, this APUS gas model stands out for higher-demand common areas or smaller multi-unit setups that need strong simultaneous hot water delivery. Its 190,000 BTU output and 8.1 GPM capacity are positioned to handle multiple fixtures at once, while the outdoor design can help free up indoor mechanical space.
Best For: Apartment buildings that need a compact outdoor unit with smart control and strong multi-fixture output.
Pros:
- 8.1 GPM and 190,000 BTU support multiple hot water points at once.
- WiFi and wired controller options make temperature adjustments easier.
- Outdoor-friendly build includes wind resistance and anti-freeze protection.
- Compact wall-mounted design helps preserve indoor space.
Cons:
- Outdoor installation may not suit every building layout.
- Requires natural gas and a 120V power source.
- Best fit is for lighter commercial or multifamily demand, not very large central systems.
This is a practical choice when the priority is efficient outdoor placement, smart controls, and solid output for shared residential hot water needs. It offers a balanced feature set without overcomplicating installation.
Compact Point-of-Use Electric Option – V7B 18kW 240V Tankless Heater
For buyers comparing commercial tankless water heaters for apartment buildings, this 18kW electric unit fits best where point-of-use hot water is needed close to showers, sinks, or laundry equipment. Its compact format and self-modulating operation make it a straightforward option for smaller service zones rather than whole-building central demand.
Best For: Point-of-use installation in apartments, common rooms, or small commercial wash areas.
Pros:
- Compact design is well suited to tight mechanical spaces.
- Self-modulating heating helps maintain steady output as flow changes.
- ETL certification and multiple safety protections add peace of mind.
- Claims up to 4.3 GPM for smaller hot water demand points.
Cons:
- Requires a 240V electrical setup with specific breaker and wiring needs.
- Best for point-of-use applications, not large central hot water systems.
- Electric capacity may be less practical where very high simultaneous demand is expected.
This model makes the most sense when you want efficient local hot water without dedicating space to a tank. It’s better viewed as a focused utility solution than a whole-building backbone.
Indoor High-Output WiFi Pick – Mizudo 199,000 BTU 10.3 GPM Indoor Unit
If you’re shopping commercial tankless water heaters for apartment buildings with heavier shared demand, this indoor natural gas model is built for higher-capacity use. Its 10.3 GPM output, 199,000 BTU rating, and support for 5 to 7 usage points make it a strong candidate for larger residential systems that need consistent hot water delivery.
Best For: Larger apartment buildings or multifamily installs needing an indoor, high-flow tankless system.
Pros:
- 10.3 GPM capacity is the highest in this group.
- Supports 5 to 7 usage points for broader household-style demand.
- WiFi and app control simplify monitoring and scheduling.
- Sealed direct vent design helps preserve indoor air quality.
Cons:
- Indoor direct vent kit is not included and must be purchased separately.
- Requires natural gas and a 120V power supply.
- Best suited to larger demand zones, not small point-of-use installs.
For multifamily properties that need stronger simultaneous hot water capability, this unit offers the most capacity and the most complete feature set here. It is the clearest fit when indoor installation and higher flow are both priorities.
Heavy-Duty Multi-Point Pick – 27kW NOVIEEX Whole-House Electric Heater
If you’re comparing commercial tankless water heaters for apartment buildings, this NOVIEEX 27kW unit is best viewed as a high-output electric option for smaller shared-use setups or larger individual suites. It’s designed for whole-house demand, with up to 7.4 GPM, support for 3 to 4 simultaneous points of use, and a compact wall-mount form that can fit tight utility spaces.
Best For: Large apartments, multi-bath units, or compact utility rooms that need strong electric on-demand hot water.
Pros:
- Up to 7.4 GPM and support for 3 to 4 water applications at once
- Wide 77°F to 140°F temperature range with 1°F adjustment steps
- High claimed efficiency at 99.8% with no standby heating losses
- 8-layer safety package including leak, overheat, dry-combustion, and pressure protection
Cons:
- Requires serious electrical capacity: 112.5A max draw and 3 double-pole 40A breakers
- Professional electrician installation is mandatory
- Best suited to installations that can support the specified power requirements
For apartment building use, this model makes sense only where the electrical infrastructure is already sized for a high-demand 240V heater. When the service matches, it offers a space-saving way to deliver steady hot water to multiple fixtures without a storage tank.
WiFi-Controlled Compact Choice – 27kW WINTEMP ETL-Certified Heater
Among commercial tankless water heaters for apartment buildings, this WINTEMP 27kW model is a practical fit for smaller residential units that need compact, on-demand hot water and remote temperature control. It delivers up to 6.5 GPM, uses self-modulating temperature control, and mounts on the wall to save space in tight utility areas.
Best For: 2–3 bathroom apartments, compact mechanical closets, and installs that benefit from WiFi monitoring.
Pros:
- Up to 6.5 GPM of continuous hot water for everyday use
- Self-modulating control helps stabilize output temperature and improve efficiency
- WiFi remote control lets you adjust temperature away from the unit
- ETL certified with leakage, overheat, and dry-fire protection
Cons:
- Recommended 200A household service and 250A supply make electrical planning important
- Limited to 6.5 GPM, so it’s not the highest-flow option in this group
- Still requires careful breaker and wiring setup for installation
If your building or unit needs a compact electric heater with app-free simplicity and better control over temperature, this one is easy to justify. It’s strongest where space is tight and hot-water demand is moderate rather than heavy simultaneous use.
Smart Flow-Control Pick – 27kW WINTEMP WiFi Tankless Heater
If you want commercial tankless water heaters for apartment buildings with a focus on temperature stability, this WINTEMP WM27V is a solid candidate for compact electric installs. It delivers up to 6.5 GPM, uses auto flow control to maintain outlet temperature, and includes WiFi app control plus usage monitoring for easier oversight.
Best For: Apartment units or small shared spaces that need smart control and steady hot water delivery.
Pros:
- Auto flow control helps keep outlet temperature steady during changing demand
- Up to 6.5 GPM and support for 2 to 4 points of use
- WiFi app control with flow and usage tracking via Smart Home/Tuya Smart
- Compact wall-mounted design with zero-energy standby
Cons:
- Requires 200A household service recommendation and 113A maximum current
- Flow may reduce slightly if demand exceeds capacity
- Not the best choice for very high simultaneous hot-water loads
This model stands out for apartments where monitoring and stable temperature matter as much as raw output. It’s a space-saving electric option that can help simplify operation, provided the installation can support the electrical requirements.
How We Picked the Best Commercial Tankless Water Heaters for Apartment Buildings
We focused on units that can serve multi-unit hot water demand with attention to BTU input, GPM output, fuel compatibility, efficiency, and commercial-ready features like smart controls, outdoor installation options, and condensing design. We also considered whether each model better suits central plant-style applications, smaller common-area installs, or point-of-use support.
Quick Comparison
For apartment buildings, the biggest split is between high-output gas models and electric tankless units. Gas units generally deliver higher flow and are better for central service or larger occupancy loads. Electric models can work well for smaller buildings, accessory systems, or locations where gas service is unavailable, but they require enough electrical capacity to support the load.
Key Buying Factors for Commercial Tankless Water Heaters for Apartment Buildings
Peak Hot Water Demand
Estimate simultaneous showers, sinks, and laundry use during busy hours. A unit that looks large on paper may still underperform if the building’s peak demand is underestimated.
Fuel Source and Utility Costs
Natural gas and propane models are usually the strongest choice for higher-demand buildings. Electric units can simplify venting and placement, but the electrical upgrade cost may outweigh the equipment savings.
Installation Constraints
Check venting, gas line sizing, service clearances, condensate drainage, and whether the unit is rated for indoor or outdoor use. These details often determine whether a model is truly practical in a multi-family property.
Controls and Serviceability
WiFi, app control, and diagnostic features can help property managers monitor performance and respond quickly to issues. Easy access for maintenance also matters when uptime is important.
Efficiency and Longevity
Condensing models are typically more efficient and may reduce operating costs over time. For buildings with steady demand, that can make a meaningful difference in total cost of ownership.
Who Should Buy Which Commercial Tankless Water Heaters for Apartment Buildings?
Choose a high-BTU gas tankless unit if you need to support multiple apartments, common-area fixtures, or large peak loads. Choose an electric model if you are serving a smaller building, need a simpler installation, or are adding supplemental hot water where gas is not practical. For larger properties, prioritize commercial-grade capacity and installation compatibility over extra features. For smaller properties or mixed-use buildings, a well-sized electric or mid-output gas unit may be the more cost-effective fit.
In short, the best Commercial Tankless Water Heaters for Apartment Buildings are the ones that match the building’s actual demand, utility setup, and maintenance plan—not just the biggest spec sheet numbers.
