Power loss recovery (PLR) is the feature that decides whether a 20-hour print survives a 5-second power blip or ends up in the bin. Implementations vary wildly by brand: some are excellent (Prusa MK4), some are good but inconsistent (Bambu), and some will leave you with a fused layer that ruins the whole part. Here's how each one works and how to maximise your success rate.
Power on, wait for the printer to detect the interrupted job, and choose "Resume". The printer re-homes (carefully avoiding the existing part), heats up, and continues from approximately the last completed layer. Expect a visible scar at the resume layer — this is normal. If the print has shifted or come off the bed during the outage, the recovery will fail when the toolhead crashes; do not force it . A small UPS rated for 5–10 minutes of printer runtime eliminates 95% of power loss problems.
Three things have to happen for PLR to work:
Steps 1 and 2 are why "power panic" is a more accurate name than "power loss recovery" — the printer has to react in the moment power is being lost. Add-on capacitors and dedicated power-loss boards (Prusa) provide the energy needed to write state to storage after mains is cut.
The gold standard. Dedicated power-loss circuit gives the firmware ~150 ms to write state. The printer drops Z to a safe distance, parks the toolhead, and stores progress. On resume it re-homes, heats up gently, then performs a "blob purge" near (not on) the print before continuing. Success rate is excellent on PLA/PETG; reduced on ABS where temperature mismatch between resumed layers shows more.
Bambu has detailed documentation on PLR; their term is "Power Loss Recovery". The feature is enabled by default; the printer detects the interruption, parks the toolhead away from the print, and on power restore offers a one-tap resume. The lid camera helps Bambu verify the print is still where it was before. The wiki specifically notes power loss recovery is supported on X1 series, P1 series, and A1 series.
Newer Creality printers (V3 series and K-series) have PLR; older Ender 3 stock did not. On supported models you'll see a "continue print" prompt at startup if a power loss happened. Reliability is brand-dependent; back up to SD card slot first.
Klipper does not have built-in power loss recovery, but several macros (TEAMGLOOMY, Mainsail's "Resume Interrupted Print") provide it. The macro reads the last-completed layer from the gcode file and skips ahead. It works but with no hardware-side power-panic interrupt, you lose any move that was in flight.
POWER_LOSS_RECOVERY is a compile-time option in Marlin. Most stock firmware enables it. State is saved to the SD card every layer (or every N seconds). It works but the save cadence means up to a layer of progress may be lost.
A small UPS (uninterruptible power supply) is the cheapest insurance against power loss problems: