Which smart home devices still work during a power outage?
Which devices keep working when the power goes out depends on three factors: how the device is powered, whether the feature needs the cloud, and whether your router and hubs stay up. This guide sorts locks, cameras, thermostats, lights, plugs, and hubs into Works, Partial, and Off so you can predict your own setup before the next outage.
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Fast answer: what still works, partly works, or turns off
| Device or system | Works | Partial | Off |
|---|---|---|---|
| Smart locks | Battery keypad, physical key, thumb-turn, and often local lock/unlock at the door | App control, alerts, guest-code changes, and automations if the hub/router/cloud path is down | Only if the lock battery is dead, the lock is mechanically jammed, or the model needs external power for the action |
| Cameras and video doorbells | Battery or solar models may keep motion detection or local recording if designed for it | Remote live view, cloud clips, notifications, and two-way talk usually fail when internet/router power is gone | Mains-powered Wi-Fi cameras and wired doorbells if their circuit, transformer, or PoE switch loses power |
| Sensors and alarms | Battery contact, motion, leak, smoke/CO, and siren functions may keep local sensing or sounding | Phone alerts, monitoring, and routines depend on the powered hub/router/internet path | Mains-powered sensors, or battery sensors whose required hub is off |
| Thermostats | Local heating/cooling control may continue if the thermostat and HVAC control power survive | App control, occupancy features, weather-aware routines, and voice control depend on network/cloud access | If the thermostat loses power, or if the furnace/air handler/boiler/heat pump system has no usable power |
| Smart bulbs and smart plugs | Usually nothing on a dead circuit | They may remember state and reconnect after power returns; battery-backed lamps are a separate product class | When the circuit feeding the bulb, lamp, or plug is out |
| Hubs, bridges, Thread border routers, Zigbee/Z-Wave controllers | Only if on a UPS or other backup power | Local automations may run if the hub and controlled devices still have power; remote control usually needs router/internet too | If the hub or bridge power supply is dead |
| Voice assistants and smart speakers | Little to nothing unless the speaker and network path are powered, and the command can run locally | Some device control may work in limited local ecosystems, but music, search, and cloud voice processing usually disappear | If the speaker, router, or internet path is down |
| Router, modem, fiber ONT, mesh nodes | Only if each required box in the chain has backup power and the service upstream is still alive | Wi-Fi inside the house may work while internet service does not, depending on what is powered | If any required power brick, ONT, modem, router, or mesh node in the path is out |
That table is the practical answer to which smart home devices still work during a power outage, but it hides the part that matters most: a device can be electrically alive and still unreachable. A smart lock with a fresh battery may open from the keypad while its app tile spins forever. A battery camera may wake up and record locally while remote live view is gone. A thermostat may still call for heat at the wall while the phone app has no idea what is happening.
This is not a rare corner case. In the 2023 American Housing Survey, about 1 in 4 U.S. households, or 33.9 million households, reported being completely without power at least once in the prior 12 months; among households that lost power, roughly 70% had at least one outage lasting six hours or more. [1]
The three-question rule
When the lights go out, stop sorting devices by category first. Sort each feature by three questions.
- Does the device itself still have power? Battery devices have a chance. Mains-powered devices on a dead circuit do not.
- Does the feature need a cloud round-trip? A keypad, local sensor, or local schedule may work. Remote live view, phone alerts, cloud video clips, and many voice commands usually need internet access.
- Is the communication path still powered? The lock, camera, sensor, hub, bridge, Thread border router, Wi-Fi router, modem, fiber ONT, and mesh node all have to be considered. One dead power brick can break the chain.
That is why outage behavior feels inconsistent. The device label says “smart lock,” “camera,” or “thermostat,” but the working part may be a much smaller feature: keypad unlock, motion detection, local recording, temperature setpoint, schedule, automation, voice command, alert, or remote viewing. Each one can land in a different column.
Smart locks: usually useful at the door, less useful from the phone
Battery-powered smart locks are one of the better outage performers, as long as the lock battery is healthy and the lock has a local way to operate. A keypad code, fingerprint reader, physical key, or interior thumb-turn does not need your router to boot. That is the part that still matters when someone is standing on the porch.
The disappointment usually starts with the app. Remote lock and unlock, activity alerts, temporary code changes, and automations often depend on some combination of hub, bridge, Wi-Fi, internet service, and vendor cloud. If the lock talks through a powered hub and the automation is local, more may survive. If the lock needs a cloud service to authorize the action or report status, the lock can be mechanically fine while the phone has stale information.
For judging a lock, do not ask only whether it “works without Wi-Fi.” Ask which action works without Wi-Fi. Opening from the keypad is not the same as receiving a notification that a child came home, changing a guest code from across town, or having a nighttime routine lock the door automatically.
Cameras and video doorbells split harder than almost anything else
A mains-powered Wi-Fi camera on a dead circuit is just decoration until power returns. The same goes for a wired doorbell camera if its transformer has no power, or a PoE camera if the network switch feeding it is not on backup power. The camera may be perfectly healthy; it simply has no electricity.
Battery and solar cameras are more interesting. They may still detect motion, wake their sensor, and in some designs save video locally. But the features people often care about during an outage—phone notifications, remote live view, cloud recording, two-way talk, and timeline access—usually need the router and internet path. If that path is dark, a camera can keep noticing things without being able to tell you about them in real time.
Local storage deserves careful wording. A microSD card, base station, or network video recorder can help only if the camera can still reach it and both sides have power. A camera with a card inside has a better chance of recording independently than a camera that saves only to the cloud, but even then behavior varies by design. Check for the exact features: local recording during internet outage, recording during power outage, and whether the camera requires the app or cloud to arm its modes.
Sensors and alarms: the siren may work before the notification does
Battery sensors can be quietly dependable. Contact sensors, motion sensors, leak sensors, smoke alarms, CO alarms, and dedicated sirens may continue their local sensing or sounding if their own batteries are good. That local behavior is the part to value first. A leak sensor that screams under the sink is still doing a useful job even if your phone never gets the push alert.
The gap appears when the sensor needs a hub to interpret the event or forward it. If the hub is off, the sensor may still detect but fail to trigger an automation. If the hub is on backup power but the router is off, a local siren routine might still run while remote alerts fail. If the hub, router, and internet path all stay up, monitoring and notifications have a better chance, assuming the service itself is available.
Thermostats: separate the wall control from the HVAC system
A smart thermostat is not useful just because its screen lights up. It has to be able to control equipment that still has power. In many homes, if the furnace, air handler, boiler, heat pump, or control transformer is out, the thermostat cannot make heat or cooling happen by itself. It can display a temperature and still be unable to move air, ignite heat, or run a compressor.
If the HVAC control power survives, local thermostat operation may continue: changing the setpoint at the wall, following an onboard schedule, or maintaining the last mode. Remote app control is a separate question. Occupancy routines, weather-dependent adjustments, alerts, and voice control may all depend on network access or cloud services even when the thermostat is still controlling the equipment locally.
For a thermostat, the useful test is plain: during a controlled test, with the internet disconnected but power still present, can the wall unit still call for heat or cooling? Then ask a different question: during a real power outage, will the HVAC equipment itself have backup power? Those are not the same problem.
Lights and smart plugs: if the circuit is dead, the smart part is irrelevant
Smart bulbs, smart switches, and smart plugs are usually the easiest call. If their circuit has no power, they are off. A bulb cannot obey a Zigbee command without electricity. A plug cannot pass power to a lamp when the outlet is dead. A smart switch cannot energize a load if there is no supply to switch.
What matters later is recovery behavior. Some lights return to their previous state, some stay off, and some come on when power returns. That is not outage operation, but it does affect what happens at 3 a.m. when the grid comes back. Check the device setting often called power-on behavior, restore state, or default state.
Hubs, bridges, and routers are the hidden outage devices
The router is not just “internet.” In a smart home, it may be the road between your phone and the device, between a hub and a cloud service, or between local controllers inside the house. A fiber ONT, cable modem, main router, mesh node, Ethernet switch, smart-home hub, bridge, or Thread border router can all be a required link. If one box is dark, the path may be broken even when the end device has battery power.
A small UPS can change the answer for some setups. If it keeps the modem or ONT, router, and hub powered, local control and some remote access may remain available. But backup power has to cover the whole chain. Powering only the router does not help if the fiber ONT is in another room with no power. Powering only a hub does not restore internet access if the modem is out. Powering only the modem does not keep Wi-Fi alive if the router is dark.
There is also a distinction between local Wi-Fi and internet service. A router on backup power may keep a local Wi-Fi network alive inside the house even when the outside service is unavailable. That can help local apps, local hubs, or locally controlled devices. It will not make cloud-only video, remote app access, or voice services magically reachable.
Protocols matter only when they change the path
Wi-Fi, Zigbee, Z-Wave, Thread, and Matter are worth knowing only to the point that they answer one outage question: what has to stay powered for this feature to work?
| Control path | Outage consequence |
|---|---|
| Wi-Fi device controlled through the cloud | Device needs power, router needs power, internet path needs to work, and the cloud service must be reachable. |
| Wi-Fi device with local app control | Device and router need power; internet may not be required for that local action. |
| Zigbee or Z-Wave device through a hub | Device and hub need power; local automations may survive if the hub runs them locally. |
| Thread device through a border router | Device and a suitable border router need power for the Thread network path. |
| Matter device | Matter does not automatically mean outage-proof. The controller, network path, and device still need power, and the feature must be locally available. |
| Cloud-only control | If internet or the vendor cloud path is unavailable, the cloud-only feature is unavailable even if the device has power. |
The trap is treating a protocol name as a guarantee. A local-capable protocol helps only if the local controller is alive. A cloud integration may be convenient every normal day and useless during an outage if the router stack is off. The correct answer sits in the path, not on the badge.
Voice assistants usually lose the job first
Smart speakers and displays are rarely the device to bet on during an outage. They need power. They usually need Wi-Fi. Many commands need cloud voice processing or cloud-connected skills. If the speaker is dark or the router is down, the usual “turn on the hallway light” command is not the fastest path to anything.
There are limited exceptions in systems that support local voice or local device control, but the same three questions still apply. Is the speaker powered? Is the command processed locally? Is the device or hub path alive? If any answer is no, use the wall control, keypad, app over local network, or physical switch instead.
How to classify your own devices before the next outage
You do not need a brand-by-brand spreadsheet to get useful answers. Walk through the house once while the power is on and mark each device by feature.
- List the battery-powered devices first: locks, sensors, cameras, smoke/CO alarms, sirens, thermostats with battery backup, and any portable lights.
- For each one, write down the local feature: keypad unlock, local alarm, motion detection, local recording, temperature setpoint, or schedule.
- Write down the cloud or network feature separately: phone alerts, remote live view, cloud clips, app unlock, guest-code changes, voice commands, and remote monitoring.
- Trace the path for the features you care about: device, hub or bridge, router, modem or ONT, mesh node, switch, and internet service.
- Decide what deserves backup power. For many homes, that means the modem or ONT, router, one central hub or bridge, and possibly a PoE switch or camera base station—not every gadget.
- Test one evening before storm season: disconnect internet service, then test again with selected equipment on backup power. Do not wait for the first real outage to discover that the “offline” feature meant something narrower than you assumed.
The answer will not be the same for every house. One lock may be a solid Works device at the keypad and a Partial device in the app. One camera may be Off because it is mains-powered; another may be Partial because it records locally but cannot send alerts. One thermostat may keep controlling heat locally while another becomes only a dark rectangle on the wall.
No smart-home category is automatically safe, and no category is automatically useless. In an outage, the useful label is simpler: powered device, local feature, powered path. If all three are present, it works. If one is missing, it is partial. If the device itself has no power, it is off.
References
- What the American Housing Survey Can Tell Us About Power Outages in U.S. Homes, U.S. Census Bureau, October 2024.
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