Keeping WiFi available during a power outage requires power for the complete local network and service from the provider. A battery powering one router does not guarantee an internet connection.
Editorial correction: Earlier versions included unsupported testing, experience or performance claims. This research guide replaces those claims. Examples below are calculations, not measurements made by Wild Smart Gear.
Map the equipment path
Identify the router, modem or fiber ONT, access points, switches and power supplies that must stay on. Some ONTs have a backup battery with limited functions; verify its documented support instead of assuming it preserves all services.
Ask your provider what depends on local infrastructure power. Battery energy at home cannot restore a failed upstream link.
Choose interruption tolerance
If equipment needs to stay running through a mains failure, compare the supported UPS/EPS arrangement and transfer time with its requirements. A station advertised as EPS may interrupt long enough for a device to reboot.
Check automatic output restart, light-load timeout and pass-through limits. Test the documented setup while an interruption is manageable, rather than discovering restart behavior during a major outage.
Work out the time budget
Use router and modem energy calculations for total load and usable battery energy. Record actual demand for the complete arrangement. Add reserve and account for any inverter overhead not already included.
If power is scarce, prioritize the access point or network area needed, and turn off optional equipment only where your setup permits. Do not alter supply voltage or use an unverified barrel adapter.
Have a communication alternative
Keep phones charged and prepare provider/emergency contact information. A mobile hotspot can help where cellular service and your plan permit, but tower availability and coverage remain external dependencies.
Record whether the outage problem is power, equipment restart or provider service. That distinction prevents buying more battery capacity to solve an upstream outage.