Navien Tankless During and After a Power Outage
On this page (6 sections)
The Short Answer: A Navien needs electricity for its fan, igniter and controls, so it makes no hot water during an outage even with gas on. It keeps its settings, but its freeze protection also needs power, so a long outage in freezing weather is the real risk. When power returns, check the outlet or breaker, turn it on, and look for codes and leaks.
During the outage
- No hot water is normal. Without power, the gas valve won’t open.
- Freeze protection is off. Navien’s NPE-2 manual says freeze protection works whether the front-panel power is on or off, as long as the electric supply stays connected. It also warns that freezing damage may occur if power or gas is interrupted, and that freeze damage isn’t covered by warranty.
- If the outage will be long and the heater is somewhere that can freeze, Navien recommends draining the unit. Draining is described in the owner’s manual: turn off the heater and gas, close the water supply, open hot taps, and drain from the unit’s drain points. If the heater is indoors in a heated space that will stay above freezing, draining usually isn’t needed.
A generator can run a Navien if it’s connected safely. The usual safe route is a transfer switch or interlock installed by an electrician, or plugging the heater’s cord into the generator, if it has a cord. Never backfeed a house circuit, and run the generator outdoors, well away from doors and windows.
When power comes back
| What you see | Likely reason | What to do |
|---|---|---|
| Display blank | Outlet, GFCI, breaker or switch still off, or a surge damaged the power supply or board | Check the breaker and any GFCI outlet; reset once |
| Display on, unit off | Front-panel power was off | Press the Power button |
| Error code shown | A fault logged during the outage or restart | Photograph it; reset once with the Back button |
| No water flows from hot taps | Frozen heater or pipes | Don’t run it; see below |
| Water dripping under the unit | Freeze damage or a fitting disturbed | Turn it off, close the water supply, call |
| Works, but recirculation schedule is off | Settings or clock need attention | Check the settings |
If the heater shows a code, look it up for your model. Navien E003 covers ignition failure, which can follow an outage if gas was also interrupted. If the display stays dark with power confirmed at the outlet or breaker, see Navien won’t turn on.
If it froze
The NPE-2 manual covers a suspected frozen heater. Turn it off, close the gas valve, open the hot tap closest to the heater, and gently warm the heat exchangers with a hair dryer or portable electric heater. Then check every few minutes for flow. Once water flows, check the heater and piping for leaks. Navien says to contact an authorized technician if there are leaks or the heater doesn’t work properly.
Don’t use an open flame or heat gun, and don’t restart the heater until water flows normally. Water leaking from inside the cabinet after a freeze usually means a cracked heat exchanger or fitting. See tankless leaking after a freeze.
Surge damage
A surge when power returns can damage the power supply or control board. Signs are a dead display with power confirmed at the outlet, a display that flickers or resets, or repeated electronics codes. A surge protector on the heater’s outlet, or a whole-house protector, can reduce the risk.
What the technician will check
A technician will confirm power at the unit and test its internal fuse and power supply. They read the fault history, check for freeze damage under pressure, and test electronics if the display is dead or erratic. If gas service was also interrupted, they may check gas pressure and confirm the burner lights cleanly.
Frequently Asked Questions
Q: Will my Navien work on gas alone during an outage? A: No. It needs electricity to run the fan, ignition and controls.
Q: Do I need to reprogram it after an outage? A: Navien’s manual says the heater keeps its settings during an outage. If something looks wrong afterward, check the settings and recirculation schedule rather than doing a factory reset.
Q: Should I unplug it during a storm? A: Unplugging protects against surges but also turns off freeze protection. In freezing weather, it’s usually better to keep it powered and use surge protection.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Navien NPE-2 Series user's information manual (opens in a new tab)Navien NPE-A2 and NPE-S2: settings retention, freeze protection, draining and thawing guidance.
- Navien: manuals and product documents (opens in a new tab)Model-specific owner information; service manuals are intended for qualified professionals.
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