Smart home devices that survive a power outage, tested

Verified Aug. 25, 2026: outage-survival matrix

The short answer: battery plus local control survives. Mains power fails unless it is backed up. Cloud control fails when the router, modem, internet path, or vendor service is gone. Matter and Thread are not magic outage shields; they keep working only as long as the controller and Thread border router behind them still have power.

That distinction matters more now because outages are lasting long enough to expose weak links. EIA utility-reported data found U.S. electricity customers averaged nearly 11 hours of interruptions in 2024, the highest annual figure in a decade, including major-event days [1]. A separate J.D. Power customer survey reported that the average longest outage rose from 8.1 hours in 2022 to 12.8 hours in 2025, with the South at 18.2 hours [2]. Those numbers do not prove any one device will fail. They do justify asking the buying question before the hallway is dark.

Test frame: grid power is out, there is no whole-home generator, and a device is judged by two things only: whether the device itself still has power, and whether the command or event can travel locally. A hub, bridge, router, modem, or border router counts as alive only if it has its own battery or is on backup power.

The labels are deliberately narrow. “Confirmed” means the device category can still perform the outage-relevant function when its local controller path is powered. “Workaround” means the function survives only with extra hardware, a specific model feature, or a paid backup path. “Fails” means the normal smart-home function stops under the test condition.

What actually breaks when the grid goes down

A smart-home outage is not one failure. It is a stack of failures that may arrive at the same time. The lock can have batteries while the hub is dead. The Thread sensor can have batteries while the border router is dark. The camera can keep writing clips to local storage while the phone shows nothing because the router and modem are off.

The layers are simple enough to test before buying:

• Device power: battery devices can still wake, sense, unlock, ring, or record. Mains-powered devices stop unless that circuit has backup power.
• Hub or bridge power: Zigbee, Z-Wave, and many Matter setups still need a powered coordinator, hub, bridge, or controller.
• Router and modem power: local app control over Wi-Fi, remote viewing, notifications, and cloud sync usually depend on this layer.
• Internet availability: a powered router does not create internet if the modem, ISP, fiber terminal, cable node, or upstream service is down.
• Cloud app availability: vendor apps may report devices offline even when a local ecosystem can still reach them.
• Voice assistant availability: speakers and displays are poor outage controls because they need power and normally depend on cloud processing.

This is why a product page saying “works during outages” is not specific enough. It has to say which layer still works. A keypad lock working at the door is not the same as remote unlock from a phone. A thermostat keeping its schedule is not the same as the heating or cooling equipment running. A camera recording to a local card is not the same as a push alert arriving while cellular service is congested.

Zigbee and Z-Wave: the cleanest survival case, if the hub is alive

Battery Zigbee and Z-Wave sensors are the easiest devices to trust during an outage because their normal job is already low-power and local: wake, report, sleep. Contact sensors, leak sensors, motion sensors, and temperature sensors do not need wall power to detect an event. They do need a powered hub or coordinator to receive it.

That hub detail is not a footnote. EVVR notes that the SmartThings v2 hub shipped with an internal battery so it could keep receiving messages from battery-powered devices during outages, while the later v3 hub did not include that internal battery [3]. SmartThings community discussion also treats hub backup power as a practical necessity, but community reports should not be weighed the same as a reproduced device test [4].

For buying purposes, a battery Zigbee or Z-Wave leak sensor is a good outage device only if the hub has power and the alert path is defined. If the hub is on a small UPS but the router is not, a local automation can still run inside some systems, but a phone notification that depends on the cloud may not arrive. That is still better than a Wi-Fi sensor that depends on the same router path for its basic reporting.

Locks sit in the same family but deserve their own judgment. A battery lock with a keypad still accepts local input when the house power is out. If it is paired over Zigbee or Z-Wave and the hub is alive, the system may also see lock state changes or run local automations. If the hub is dead, the lock has not become useless; it has become a keypad lock.

Matter and Thread: local does not mean self-powered

Matter improves local control, but it does not remove the need for powered infrastructure. A Thread device still needs a Thread border router. A Matter-over-Wi-Fi device still needs Wi-Fi. A phone may still need to be on the same local network. If the product’s only powered controller is a smart speaker plugged into a dead outlet, the “local” promise has nowhere to run.

The best documented public case is Matter Alpha’s offline test, where Matter devices remained controllable through Apple Home while some vendor apps showed the same devices offline. That was a single hands-on Starlink, UniFi, and Apple Home setup, not a universal guarantee, but it captures the separation buyers need to care about: the ecosystem’s local path may survive even when the vendor app path does not [5].

For Thread sensors and locks, the purchase rule is therefore stricter than “supports Matter.” Identify the Thread border router. Identify the controller that will issue or receive commands. Then decide whether both are on backup power. A battery Thread sensor with a dead border router is just a quiet sensor.

Matter-over-Wi-Fi devices should be treated closer to Wi-Fi devices than to sleepy Zigbee sensors. They may have a better local command model than older cloud-only products, but they still depend on the local Wi-Fi layer being powered. If the router is on a UPS and the phone is on the same network, local control may continue. If the router is dark, the protocol label does not rescue it.

Wi-Fi devices and vendor apps fail at the network layer

Wi-Fi is not automatically fragile, but most Wi-Fi smart-home products are built around a path that includes the outlet, router, modem, internet, and vendor cloud. During a grid outage, that is too many pieces to assume alive.

A mains-powered Wi-Fi plug, bulb, switch, display, or speaker fails first because it has no power. A battery Wi-Fi camera or doorbell may still have power, but remote viewing and push alerts usually need the home network and internet path. A vendor app can be beautifully designed on a normal day and still be the wrong control surface when the router is dark.

The exception is not really an exception; it is backup infrastructure. Put the router, modem, base station, or camera bridge on a properly sized UPS, and some Wi-Fi devices regain a usable local or remote path. Add cellular backup, and alerts or remote access may continue even if the home internet line is down. That is a workaround, not the default behavior of a Wi-Fi device.

Device-category notes that matter during the outage

Locks

Buy a lock for outage use only after separating entry from connectivity. Manufacturer guidance from EZVIZ says smart locks can continue operating from their internal batteries during a power outage, and eufy similarly describes battery-powered lock operation and backup entry methods for dead-battery situations [6][7]. Those are manufacturer statements, so they should be read as model-specific claims rather than independent tests across the whole category.

The practical grade is still clear: keypad or physical backup entry is the survival feature. Remote lock/unlock, cloud logs, guest-code sync, and voice control are conveniences that depend on other powered layers.

Sensors

Battery sensors are the strongest smart-home outage buy when they use a local low-power protocol and the hub is backed up. Leak detection is the obvious case: the valuable event may happen while no one is standing near the device. The sensor’s battery is only half the test. The hub, siren, local automation, or notification route has to survive too.

Thermostats

Thermostats should be judged at the wall first. Honeywell’s support guidance says thermostats with backup batteries can retain schedule and continue on-unit operation when power or internet is interrupted [8]. That does not mean the furnace, air handler, compressor, or boiler has power. It means the control device may keep its settings and local interface.

For a buyer, the right question is not “Is this thermostat smart?” It is “What can I still change at the thermostat if Wi-Fi and the app are gone?” If the answer requires a cloud login, it is not an outage control.

Cameras and video doorbells

Cameras split into three different functions: power, recording, and access. A battery camera may still have power. If it has local storage or a powered base, it may continue recording. Remote live view, cloud clips, and push alerts usually need the router, modem, and internet path.

Outage-prep guidance commonly treats battery cameras and local recording as useful, while noting that remote streaming depends on network power; cellular backup can restore alerts or access, but typically as an added paid service or separate hardware path [9][10]. That makes battery cameras a “workaround” category, not a clean “confirmed” category.

Hubs, bridges, routers, and border routers

These are the devices people forget because they are not the sensor on the door or the lock in the hand. They are also the devices that decide whether battery smart-home gear remains smart during the outage. A Zigbee hub, Z-Wave hub, Matter controller, Thread border router, Wi-Fi router, modem, camera base station, and alarm bridge should be treated as infrastructure.

Do not size a UPS from this article. The runtime math belongs in the separate smart-home outage gear compatibility guide. Here, the buying rule is enough: if a device requires a hub, bridge, router, or border router, that box needs backup power before the device earns an outage-survival grade.

Voice assistants and smart displays

Voice assistants are not dependable outage controls. They are usually mains-powered, cloud-dependent, and routed through the same network stack that just failed. If a household member needs to unlock a door, silence a siren, see a leak alert, or change a thermostat during an outage, the control should exist without asking a speaker to understand a command.

How to use the matrix before buying

For any device on a product page, trace the outage path in this order:

1. What powers the device itself during the outage?
2. What receives its signal or sends its command?
3. Is that receiver local, cloud-only, or mixed?
4. Does the required hub, bridge, router, modem, or border router have backup power?
5. What still works if the vendor app says the device is offline?

If the answer is “the keypad still works,” that is a real survival feature. If the answer is “the app should notify me,” keep tracing until you find the powered device and the network path that make that notification possible.

For a faster device-by-device pass, use the storm-outage survival checklist. For the broader household sequence before, during, and after a storm, use the smart-home storm preparedness checklist. If the power has already returned and devices are still offline, switch to the recovery guides for smart devices offline after a power outage and reconnecting devices after an outage. To confirm whether the problem is the grid or only your house, use the outage-tracking guide for checking power outages near you.

Protocol choice predicts resilience because it usually predicts whether the device is battery-powered, locally controlled, and hub-dependent. It does not prove survival by itself. The device, the hub or border router, and the control path all need power before “works during outages” becomes true.

References

1. U.S. electricity customers experienced nearly 11 hours of interruptions in 2024, U.S. Energy Information Administration, Dec. 2025.
2. Power outages, extreme weather, JD Power, Utility Dive, Nov. 2025.
3. What Happens to Your Smart Devices During a Power Outage, EVVR.
4. Battery Backup Necessity, SmartThings Community.
5. Do Matter Devices Work Without Internet?, Matter Alpha.
6. How smart locks work during a power outage, EZVIZ.
7. What Happens If Smart Lock Battery Dies? Everything You Should Know, eufy.
8. What happens if the power or internet go out?, Honeywell Home.
9. Surviving a Smart Home Power Outage, Americas Generators.
10. Best Home Tech Buys to Help During Power Outage, CNET.