Short outages (under ~20 minutes) — The plug stores measurement data locally and uploads it when the connection returns. You won't lose any detail
Longer outages (over ~20 minutes) — On-device storage fills up, so per-minute detail may be lost. The plug continues tracking cumulative usage and averages it across the outage period when it reconnects. Totals will be correct but fine-grained data won't
App control while offline — Not available. Without a Wi-Fi and cloud connection, the plug can only be controlled using the physical power button on the device itself
Schedules while offline — Continue to work. Schedules are stored locally on the plug, so scheduled on/off events still fire during an outage. Changes to schedules require the plug to be back online