What Happens to Your Alarm in a Power or Internet Outage
There are no affiliate links on this page. No alarm company or monitoring provider paid to appear here or influenced what it says. Read our full disclosure.
Short answer: most current alarm panels keep sensing and sounding the siren on battery for a period the vendor states, from 4 to 6 hours on ADT's Command, Pulse and legacy panels to "up to 24 hours" on SimpliSafe, Ring and ADT's newer hubs. What usually stops first is not the alarm but the path out of the house: if the panel reaches the monitoring center over your Wi-Fi, a power cut takes your router down with it, and the signal only gets out if the system has a working cellular path. On most self-install systems that cellular path is a feature of a paid plan, not of the hardware.
Four things fail separately
An outage is easier to plan for if you stop thinking of "the alarm" as one thing. Four parts behave differently:
- The panel or base station. Runs on its own backup battery for the time the vendor states. Door, window and motion sensors are battery powered anyway, so they keep reporting to it.
- The route to the monitoring center. Wi-Fi or Ethernet needs your router and modem powered. A cellular radio in the panel does not, but on most systems it only carries alarm signals when a plan that includes it is active.
- Cameras and video doorbells. Wi-Fi cameras stop sending when the router goes down. Cove says so plainly: its cameras "will stop transmitting during a power outage, but all other sensors will continue working."
- Your phone app. Ring's support page states that if the Base Station goes offline "you will be unable to access or control your devices through the app", while the system stays armed and the siren still works.
What each system's maker says
| System | Panel backup battery (vendor's words) | If the internet goes down | What the vendor says still works |
|---|---|---|---|
| SimpliSafe | "up to 24 hrs" | Switches to its built-in cellular connection, which requires a professional monitoring plan | During a power outage, arming and disarming is by Keypad only; app control returns when power does |
| Ring Alarm | "up to 24 hours", depending on usage | Cellular backup "requires a compatible Ring subscription" | Normal for 15 minutes on battery, then sensors and alarm signals only; system stays armed and siren works if the Base Station goes offline, but the app cannot control it |
| ADT Command, Pulse and legacy panels | "typically lasts 4 to 6 hours" | Not stated on the page we read | Low-battery beeps until the battery is depleted |
| ADT Self Setup and Smart Home (Smart Home Hub, ADT Base) | "a backup battery that last 24 hours" | ADT says communications "may still be disrupted" unless the router and modem have battery backup, and that this equipment "must have at least 8 hours of backup battery" | Not stated beyond the communications warning |
| Cove | Panel and sensors "at least 24 hours" | Cove describes its system as wireless and not dependent on phone lines | All sensors keep working; Wi-Fi cameras stop transmitting |
| Abode | Not stated on the plans page we read | Cellular backup is listed as part of the Pro plan ($26.99 a month or $245.99 a year, read 2026-09-24), not the Standard plan | Not stated on the plans page we read |
"Up to" figures are maximums under the vendor's own assumptions. A battery that is several years old will not deliver them, which is the reason for the test further down. SimpliSafe also tells customers who have had their system since 2019 or earlier that it may be time to update the network backup.
Cellular backup is usually something you pay for
This is the point most buyers miss. The cellular radio is inside the base station whether or not you pay for it. On SimpliSafe it carries alarms only "with a professional monitoring plan"; on Ring it needs "a compatible Ring subscription"; on Abode it sits in the Pro plan. If you self-monitor for free and your power or internet drops, the siren may still sound in an empty house, but nothing reaches your phone or anyone else. If outages are common where you live, that is a better reason to pay for a plan than most of the features plans are sold on. Our monitoring cost comparison shows what each tier costs per month, and systems with no monthly fee covers what you give up by not paying.
If your alarm still uses a phone line
Older panels dial the monitoring center over a phone line. If your phone service has moved from copper to fiber, cable or VoIP, the line itself needs power at your end. FCC rules require providers of that kind of home phone service to offer a backup power option with at least 8 hours of standby power at the point of sale (from 13 February 2016 for larger providers), and at least one 24-hour option from 13 February 2019. The FCC's own sample customer disclosure is blunt about what that battery covers: "Home security systems, medical monitoring devices and other equipment will not run on a home phone backup battery." In other words, a phone backup battery keeps the phone line alive; your alarm panel still depends on its own battery.
If you have inherited a panel that dials out over a landline, our guide to taking over an inherited alarm system covers the move to a cellular communicator.
When the power comes back
ADT states that a panel battery takes 24 to 48 hours to recharge after power is restored, and that the low-battery message should clear once it has. Until then the panel may keep beeping. If the beeping continues after two days, the battery is likely at the end of its life; see why an alarm panel keeps beeping and, for ADT panels, replacing an ADT panel battery.
The outage test: 15 minutes, twice a year
Before you start: if you have professional monitoring, contact your provider or use the app to put the account into test mode first. Without that, tripping a sensor during the test can produce a real dispatch, and in many cities a false-alarm fine (see our false-alarm fine index).
- Unplug the base station or panel from mains power (leave the router on for now). Confirm it shows that it is on battery: a battery icon in the app, a flashing light, or a trouble tone.
- Trip one door sensor. Confirm the siren or chime works and, with test mode on, ask the monitoring center or check the app that the signal arrived.
- Now switch off the router and modem. This is the real outage. Trip the sensor again and confirm the signal still arrives. If it does not, you do not have a working cellular path, whatever the box says.
- Check your cameras. Expect Wi-Fi cameras to be offline. If you rely on one, decide whether it needs its own backup power or local storage.
- Restore power to everything, confirm the panel reports mains power again, and take the account out of test mode.
- Write down the date and the battery's age. If the panel complained about its battery within the first hour, replace the battery before the next storm, not during it.
If you own a second home that sits empty through winter, the same logic applies to the sensors that matter most there; see freeze and leak sensors for a second home.
Common questions
Will my home alarm work during a power outage?
The panel will, for as long as its backup battery lasts: vendors state from 4 to 6 hours (ADT Command, Pulse and legacy panels) up to 24 hours (SimpliSafe, Ring, ADT Smart Home Hub, Cove). Whether anyone is told about an alarm depends on whether the system has a working cellular path, since a Wi-Fi route fails with your router.
Do I need to pay for cellular backup?
On the self-install systems we checked, yes. SimpliSafe ties it to a professional monitoring plan, Ring to a compatible subscription, and Abode lists it in its Pro plan rather than Standard.
Will a home phone backup battery keep my alarm running?
No. The FCC's sample disclosure for phone providers states that home security systems and medical monitoring devices "will not run on a home phone backup battery." It keeps the phone line powered, not the panel.
Next step: run the 15-minute test above, then read professional versus self-monitoring with what you learned. If the test showed no cellular path, the monitoring cost comparison shows the cheapest plan on each system that includes one. More tools: all resources.
About this page
Every figure above is quoted from the vendor's own support or plans page, or from the FCC, read in a browser on 2026-09-24; the SimpliSafe and ADT pages were read again on 2026-09-25 and matched. Where a vendor does not publish something we say "not stated on the page we read" rather than filling the gap from another site. We have not tested any of these systems in an outage. This is general consumer information; if your panel also handles smoke, heat or carbon monoxide detection, ask your installer before powering it down. See our methodology and editorial policy; substantive changes are listed on our corrections page.
Sources
- SimpliSafe Support, "Will My SimpliSafe System Still Work if I Lose Power or Wi-Fi Connection?" (page updated September 3, 2026): up to 24 hours on battery, cellular backup with a professional monitoring plan, Keypad-only arming during an outage (accessed 2026-09-24 and 2026-09-25)
- Ring Support, "What to Know if Your Ring Alarm Goes Offline": battery life, cellular backup subscription requirement, app control when offline (accessed 2026-09-24)
- ADT Help, "Severe Weather and Your ADT System": 4 to 6 hours on Command, Pulse and legacy systems, 24 hours on Smart Home Hub and ADT Base, 8-hour router and modem backup, 24 to 48 hour recharge (accessed 2026-09-24 and 2026-09-25)
- Cove, "Power Outage: Will Cove Home Security Systems Work?" (accessed 2026-09-24)
- Abode, Plans and Pricing: Standard and Pro plan prices, cellular backup listed under Pro (accessed 2026-09-24)
- FCC, Small Entity Compliance Guide: Ensuring Continuity of 911 Communications, DA 16-475, 29 April 2016: 8-hour and 24-hour backup power options and sample customer disclosure (accessed 2026-09-24)