Short answer
A monitored alarm panel usually keeps working in a power outage on its backup battery, and a cellular communicator lets it keep reporting if the internet goes down too. Wi-Fi cameras, routers, and other plug-in devices often stop unless they have separate backup power. How long the panel lasts depends on its battery and what it powers.
In this article
Does a security system work during a power outage?
A professionally installed alarm panel usually keeps working during a power outage, because it has a backup battery that takes over when mains power drops. How long it lasts depends on the panel, the battery's age, and the devices it powers. Cameras, Wi-Fi routers, and other plug-in devices often stop unless they have their own backup.
The switch to battery happens automatically, and many panels send a power-loss signal to the central station so the monitoring company knows the system is running on backup. The panel keeps reading sensors, sounding the siren, and sending alarms as long as the battery holds and a communication path is available. Exact backup times vary by equipment and configuration, so the right figure for a given system comes from the provider, not a general rule.
What happens to the system if the internet goes down?
If a system reports to the central station only over the home internet, an internet outage can stop signals from reaching the station, even while the panel still detects events locally. Systems with a cellular communicator can keep reporting over the cellular network. App control and camera streaming that rely on the home network may stop until it returns.
A power outage usually takes the internet down with it, because the modem and router are plugged into the wall. That is why the communication path matters as much as the panel battery. A system with internet as its only path effectively loses monitoring in a long outage, while a system with cellular, alone or as a backup, can keep reporting. Our comparison of cellular and landline alarm communication explains the trade-offs between those paths.
Which parts of a system usually stop working in an outage?
The parts most likely to stop are those powered from a wall outlet without backup: Wi-Fi cameras, the home router, video recorders, and some smart-home devices. Battery-powered wireless sensors keep working as long as the panel is running. Hardwired devices powered by the panel run on the panel's battery, which shortens how long the battery lasts during a long outage.
Battery-powered cameras may keep recording to local storage, but without the router they cannot upload clips or send alerts until the network returns. Smoke detectors deserve a separate check: hardwired smoke alarms normally include their own backup battery, while smoke detectors connected to the alarm panel depend on the panel. Many electronic locks run on their own batteries and keep working. Garage door openers and motorized water valves vary by model, so it is worth checking how each one behaves without power before an outage, not during one.
How can you keep a system running through a long outage?
To keep a system running through a long outage, confirm the panel battery is in good condition, make sure the system reports over cellular and not only internet, and consider a separate backup power supply for the router and key cameras. Ask the provider what backup the system has and what the panel reports when the battery runs low.
Panel batteries wear out with age and should be tested and replaced on the schedule the manufacturer or provider recommends; a panel warning of a low battery is asking for that replacement. A small battery backup unit for the modem and router keeps internet-dependent cameras and app access alive for longer, though it will not run them indefinitely. Homes with a standby generator should confirm which circuits it covers. Backup for power and internet outages is one of the points professional alarm monitoring should address in writing for each property. For the other questions that shape the choice, see our guide to choosing a home security system.