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Every security system has a quiet assumption behind it: that the electricity is on and the internet is up. Both of those fail, and they often fail together, which is exactly when a house is emptier and darker than usual.
You do not need to engineer around every scenario. You need to know what your specific system does, which takes one afternoon and no money.
The two questions
How long does the panel run on battery? Control panels have a backup battery, usually sealed lead-acid or lithium, rated in hours. The rating assumes a healthy battery, and batteries age out in a handful of years. The practical question is not the rating but the measurement: unplug it and watch.
How does it report when the internet is down? There are three common paths:
- Broadband only. Cheap, and offline the moment the router loses power or the line drops.
- Cellular. A radio in the panel reports over a mobile network. This is what makes a monitored system survive a cut line.
- Dual path. Broadband with cellular failover, which is what most monitored systems should be.
The cellular detail worth asking about
Cellular radios are built for a particular generation of mobile network, and networks get retired. Alarm panels have been stranded by that before: a panel bought with the newest radio of its day eventually sits on a network the carrier has switched off, and the signal path quietly stops working.
So ask two things when buying or renewing:
- Which network generation does the radio use?
- What is the process, and the cost, when that generation is retired? Is it a module swap or a new panel?
A monitoring company that answers both clearly is telling you something good about the rest of its service.
What happens to the cameras
Cameras are the part that fails first, and people are surprised by it.
- Cloud cameras need the internet to upload. No router, no recording, whatever the plan says.
- Wired cameras with a local recorder keep recording if the recorder has power, even with the internet down, but you cannot watch remotely.
- Battery cameras keep their own power but still need a network to send anything.
- Video doorbells usually draw from the doorbell transformer, which is mains powered, so they stop with the house.
The cheap fix for most of this is a small uninterruptible power supply for the router and the recorder. An hour or two of runtime covers the majority of outages, which are short.
If your security depends on the router, put the router and the modem on a battery backup and label it. It is the least glamorous purchase in home security and one of the few that quietly improves everything connected to it.
The two tests, twice a year
Power test. Tell the monitoring company you are testing. Unplug the panel from the wall and note the time. Check that it reports the power loss, and see how long it stays alive. If the runtime is a fraction of the rating, the battery needs replacing, which is a cheap part.
Signal test. With the panel still powered, unplug the router. Trip a sensor. Confirm the signal still reaches the monitoring company, which is the proof the cellular path works. Then plug everything back and confirm the system reports restoration.
Write the date and the result somewhere. Two test results a year apart tell you when the battery is fading.
Where the alarm sits in a real outage
A wider outage brings other problems with it, and the alarm is rarely the most urgent. Keep the house’s outage kit in one place: torches with charged batteries, a phone power bank, and the phone number of the monitoring company written down rather than only stored in the phone that may be flat.
And check the smoke alarms while you are there. Mains-powered smoke alarms have their own backup batteries, and the device most likely to save a life in a dark house is the one that costs the least.
Related reading: What Home Security Costs After the First Bill and Alarm Contracts and the Knock at the Door.
Questions people ask
Does a home alarm work without power?
For a while. Panels have a backup battery, typically rated for several hours, but the real runtime depends on the battery's age. Test it by unplugging the panel and timing how long it reports on battery.
Will my alarm still call the monitoring company if the internet goes down?
Only if it has a cellular path. Systems that report over home broadband alone stop reporting when the router loses power or the line fails. Dual-path systems fail over to cellular, which is what a monitored system should have.
Do security cameras work during a power outage?
Usually not. Cloud cameras need the router to upload, and video doorbells generally run from a mains-powered transformer. A small battery backup on the router and any local recorder covers most short outages.
Why did my old alarm stop reporting after a network change?
Cellular radios are built for a specific network generation, and carriers retire old generations. When that happens, panels with an obsolete radio lose their signal path and need a module swap or replacement. Ask which generation your radio uses.
Where these figures come from
- Power Outages Ready.gov, US Department of Homeland Security · ready.gov
- Smoke Alarms US Fire Administration, FEMA · usfa.fema.gov
- False Burglar Alarms, 2nd Edition, Problem-Oriented Guides for Police No. 5 US Department of Justice, Office of Community Oriented Policing Services · portal.cops.usdoj.gov
Figures last checked September 2026.
