You accept the use of cookies as described in our Privacy Policy by clicking 'OK'.
Condensing Tankless Water Heaters
The proven ultra-high-efficiency, eco-friendly, space-saving way to supply endless domestic hot water for homes and businesses.
View All Navien Condensing Products
How Condensing Tankless Water Heaters Work
Ultra high-efficiency tankless water heaters—also known as condensing tankless—use two heat exchangers to supply endless hot water when you turn on a faucet. They use less energy (and money) than traditional water heaters because they don't need to reheat the water over and over.
When a hot water tap is opened, the tankless water heater detects the flow
The flow sensor activates to determine the amount of hot water needed
The igniter activates
The gas control valve opens to supply the correct amount of gas
The fan and venturi activate to provide the correct amount of gas and fuel
The premix burner ignites providing a flame to heat the water
Cold water is pre-heated in the secondary heat exchanger
Pre-heated water passes from the secondary to the primary heat exchanger
The unit determines outgoing set temperature and adjusts the flame to heat the water
Heated water moves to the buffer tank
Desired hot water amount delivered to the faucet
When a hot water tap is opened, the tankless water heater detects the flow
The flow sensor activates to determine the amount of hot water needed
The igniter activates
The gas control valve opens to supply the correct amount of gas
The fan and venturi activate to provide the correct amount of gas and fuel
The premix burner ignites providing a flame to heat the water
Cold water is pre-heated in the secondary heat exchanger
Pre-heated water passes from the secondary to the primary heat exchanger
The unit determines outgoing set temperature and adjusts the flame to heat the water
Heated water moves to the buffer tank
Desired hot water amount delivered to the faucet
What’s the difference between condensing & non-condensing tankless water heaters?
Condensing gas tankless water heaters include a second heat exchanger which uses heat from the exhaust gas to preheat incoming cold water. This technology increases the hot water flow rate, improves energy efficiency, and lowers the exhaust gas temperature.
Cooler exhaust means you have a wider range of venting material options, including PVC and polypropylene. Because water vapor condenses inside the unit as the exhaust gas cools, condensing tankless water heaters require a drain (and potentially a pH neutralizer) to dispose of the acidic condensation water.
Non-condensing tankless water heaters have a single heat exchanger and do not recycle heat from the exhaust gas. Because the exhaust gas is very hot when it leaves the unit, metal concentric venting is required. Because water vapor does not condense inside the unit, there is no drain required for installation.
Are condensing tankless water heaters better than non-condensing?
It depends on your priorities:
Condensing tankless water heaters offer higher flow rates, an efficiency rating of up to 0.96 UEF, and allow the use of more cost-effective venting materials such as polypropylene or PVC. But condensing units require a drain, which can limit your installation location options.
Non-condensing tankless water heaters are smaller than comparable condensing models and offer more flexibility for installation since they don't need a drain. Non-condensing units have an efficiency rating of 0.81 UEF, which is still far more efficient than tank-style water heaters.
Condensing Water Heater FAQ'S
What does condensing mean in a tankless water heater?
As water is heated, the burner creates hot exhaust gas. Condensing tankless water heaters use the heat from exhaust gas to preheat cold water, making them very energy efficient. As it cools, the exhaust gas condenses and turns into water vapor which eventually flow out to the drain.
Do condensing tankless water heaters need a drain?
Yes, condensing tankless water heaters need a drain for the condensation water that forms in the secondary heat exchanger.
How do you vent a condensing tankless water heater?
Condensing tankless water heaters can be vented through a wall or the roof, up to 75 feet with 2” vent pipe. Because condensing tankless water heaters have relatively cool exhaust gas, you can use 2” PVC or rigid/flexible polypropylene venting. Condensing tankless water heaters cannot share venting with other appliances, and cannot be vented through a chimney.
Condensing vs Non-Condensing
Tankless Water Heaters
| Condensing | Non-Condensing | |
| Initial cost | Usually higher than comparable non-condensing | Usually lower than comparable condensing |
| Long term operating cost | Lower than typical non-condensing tankless and storage tank system | Could be higher than condensing but lower than storage tank systems |
| Efficiency | Ultra-high Efficiency (UEF up to .96) | High Efficiency (UEF > .80) |
| Maintenance requirement | Annual service recommended | Minimal |
| Venting | PVC acceptable | 3" x 5" metal concentric required |
| Installation Location | Indoor or Outdoor | Choice of interior or exterior |
| Durability | Stainless steel heat exchanger extend service life | Stainless steel heat exchanger extend service life |
| Dimensions | Slightly larger than non-condensing, about 70-80% smaller than tank system | Slightly smaller than condensing, 80% smaller than tank system |
Navien Condensing Tankless Water Heaters
The Navien NPE-2 series is a line of high-efficiency condensing tankless water heaters featuring a user-friendly control panel. These tankless water heaters can be installed indoors or outdoors, for residential or commercial use.
Navien NPE-2 High Efficiency Condensing Tankless Water Heaters
NPE-A2 Series
Advanced condensing tankless water heaters featuring Navien’s patented ComfortFlow® system.
ComfortFlow® includes a buffer tank, recirculation pump and fine-tuned controls which resolve the “cold water sandwich” effect and flow rate issues common in other tankless water heaters.
NPE-180A2
Max Input: 150,000 BTU/h
Indoor or outdoor wall-hung
Residential/Commercial
ComfortFlow® Technology
NPE-180A2
NPE-210A2
Max Input: 180,000 BTU/h
Indoor or outdoor wall-hung
Residential/Commercial
ComfortFlow® Technology
NPE-210A2
NPE-240A2
Max Input: 199,900 BTU/h
Indoor or outdoor wall-hung
Residential/Commercial
ComfortFlow® Technology
NPE-240A2
NPE-S2 Series
Navien’s standard ultra high-efficiency condensing tankless water heaters.
NPE-150S2
Max Input: 120,000 BTU/h
Indoor or outdoor wall-hung
Residential/Commercial
ComfortFlow® Technology
NPE-150S2
NPE-180S2
Max Input: 150,000 BTU/h
Indoor or outdoor wall-hung
Residential/Commercial
ComfortFlow® Technology
NPE-180S2
NPE-210S2
Max Input: 180,000 BTU/h
Indoor or outdoor wall-hung
Residential/Commercial
ComfortFlow® Technology
NPE-210S2
NPE-240S2
Max Input: 199,900 BTU/h
Indoor or outdoor wall-hung
Residential/Commercial
ComfortFlow® Technology
NPE-240S2
Navien NPE-2 Series condensing tankless water heaters deliver an endless supply of hot water for any size home.
Besides providing hot water where and when it’s needed, the NPE-2 Series offer homeowners the following benefits:
- Much more energy efficient than old fashioned tank systems
- Ultra high energy efficiency —
up to 0.96 UEF - Backed by the industry's strongest warranty – 15 years on heat exchangers
- Energy Star certified
- Takes about 80% less space than old fashioned tank heaters
- Longer lasting than tank heaters
- Easy to use control panel
- Elegant, clean appearance
- Improves resale value
- Ideal for replacements or new construction
Benefits of Navien Condensing Tankless Water Heaters
The Ultimate Endless Hot Water Solution For Your Home
Durable, Long-Lasting Construction
Navien NPE-2 condensing tankless water heaters use durable dual stainless steel heat exchangers.
Eco-Friendly
Condensing technology reduces energy consumption and greenhouse gas emissions.
Control from Your Phone
Optional NaviLink™ Wi-Fi control system gives you access to your Navien systems from anywhere in the world.
Multiple venting options
For homes with extra high demand, NPE-2 Series units can be cascaded without an external control.
On-demand Recirculation
HotButton on-demand recirculation option with built-in controller.
Optional Forced Air Systems
H2Air combination space heating and domestic hot water supply optional for NPE-A2 models.
The ultimate in energy efficiency
Navien condensing technology provides up to 0.96 UEF. These extremely efficient and eco-friendly units provide extra energy savings over traditional tank and non-condensing tankless water heaters.
Operating Cost
Protect the environment
as you add value
Navien condensing stainless steel heat exchangers recover extra heat that would be lost in non-condensing boilers. The result is a reduction in energy consumption, lower CO2 emissions and low exhaust temperatures allowing the use of less expensive venting materials such as Schedule 40 PVC.
Find a Navien Tankless Water Heater Installer Near You
Find an Installer
