Why Does My Smart Plug Turn Off by Itself? Four Triggers

A smart plug that switches off on its own is almost always obeying a rule, not failing. Overcurrent or over-temperature protection, a cloud watchdog responding to a Wi-Fi dropout, a load-sensing outlet misreading current draw, and a firmware power-loss setting defaulting to Off cover nearly every case.

Re-pairing the plug rarely helps, because pairing has nothing to do with any of those four triggers. The events are recorded. TP-Link Kasa logs an overcurrent trip under Usage or Alerts in the app, and most Wyze and Amazon Basics plugs keep a similar history. Read it before you touch the router.

The number that catches people out is the gap between the rating on the box and the trip point inside it. A plug sold as 15 A typically cuts at 16–18 A, and a 1500 W space heater on a 120 V circuit draws 12.5 A steady while spiking well above that at switch-on. A fan or a lamp will never do this. A heater, a hair dryer, or a kettle will.

Then there is the quieter failure. Many plugs ship with Power On State set to Off, so a two-minute outage at 3 a.m. leaves your lamp dark until you notice.

• Overcurrent trips first: Most 15 A smart plugs cut power at 16–18 A, and a 1500 W space heater on 120 V draws about 12.5 A continuously with brief higher inrush.
• Watchdog needs three misses: A cloud watchdog resets the relay after 3 consecutive missed heartbeats, usually spaced 30–90 seconds apart, so a brief dropout can still cut power.
• Load sensing cuts at 5 W: Load-sensing outlets detect current falling below roughly 5 W and kill power after a 10–30 minute delay, which is common with phone chargers and TVs in standby.
• Power On State defaults to Off: The firmware option accepts Off, On, or Last State, and Off is the factory default on many models including several Kasa and Amazon Basics units.
• Matter 1.3 added energy reporting: Released in 2024, it supports power and energy reporting, but plenty of hubs still do not surface those values to the user.

What does the smart plug's event log actually tell you?

Every mainstream smart plug keeps a short local history, and reading it takes about three minutes if you know where the labels live. This applies to Wi-Fi plugs on a 2.4 GHz network (TP-Link Kasa, Wyze Plug, Amazon Smart Plug) and to hub-connected gear on Zigbee, Z-Wave, or Matter 1.3. You need the plug's own app or hub dashboard open, plus a rough memory of what else in the house was running when the shut-off happened.

1. Open the manufacturer app and find the diagnostics pane. In Kasa it's the plug tile, then the graph icon, then Usage. In Wyze it's Settings > Device Info > Power Usage. In SmartThings, open the device, tap History. Apple HomeKit and Matter 1.3 devices are the weak spot here: HomeKit stores almost nothing, so check the plug maker's own app first and treat HomeKit as a control surface, not a log.
2. Switch to the alerts tab, not the usage tab. Usage shows watts over time and tells you the load shape. Alerts shows why power stopped. Look for four specific strings: Overcurrent, Overload, Watchdog, and Power Loss Recovery. If you see none of them, the plug was told to turn off by something outside itself, which points at automation, a voice routine, or a scheduled scene.
3. Write down the timestamp before you interpret anything. This is the step people botch. They see an overcurrent alert, replace the plug, and never check whether the trip at 18:42 matched the moment the space heater kicked in. Set the log next to your router's connection log and your hub's activity feed. Three clocks agreeing on one minute is a diagnosis. One clock alone is a coincidence.
4. Read the trip threshold against the load. Most US smart plugs carry a 15 A continuous rating and trip somewhere between 16 A and 18 A, model-dependent, per their 2025-2026 spec sheets. A 1500 W heater on 120 V draws 12.5 A on its own. Add a 300 W lamp and you are at 15 A, sitting on the rating with no headroom for the compressor or element surge. The plug is doing exactly what UL 498 testing says it should.
5. Check whether the shut-off is a watchdog event rather than a fault. Cloud watchdog routines ping the plug on a 30 to 90 second heartbeat; miss enough of them and the firmware drops the relay as a fail-safe. On Wi-Fi this usually means a 2.4 GHz band problem: a mesh node reassigning the plug, a firmware update on the router, or channel congestion from a neighbour. Zigbee and Z-Wave plugs on a local hub rarely show this, because the heartbeat never leaves the house.
6. Rule out load-sensing mode. Plugs sold as energy-saving outlets (some Wyze and Amazon firmware builds) cut power 10 to 30 minutes after the attached device drops below roughly 5 W. A phone charger at 3 W or a lamp on a dimmer at its lowest step will trigger this. The log typically shows a clean off with no fault code, which is the tell.
7. Correlate with non-plug events. Check whether the shut-off lines up with the fridge compressor, a microwave, a vacuum on the same circuit, or a scheduled firmware update window. Whole-home brownouts below about 90 V can also cause a relay drop followed by a Power Loss Recovery entry. That last label does not mean the plug failed; it means the plug rebooted and restored its last state, which is the correct 0.5 to 1.5 W standby behaviour. Compare the count: one recovery event in six months is noise, four in a week is a wiring or supply problem.

The failure mode is reading the log after you have already changed something. If you re-pair a plug, update firmware, or move it to another outlet before you pull the history, the timestamps no longer line up with the conditions that caused the trip and you have thrown away your only evidence. Pull the log first, photograph it, then act. And if the log is genuinely empty on a plug that keeps cutting out, suspect the load-sensing firmware branch or a cloud account issue before you suspect the hardware, because a dead relay does not produce a clean, repeatable 30-minute delay.

Is overcurrent protection tripping?

Every smart plug has a relay and a current-sensing circuit, and that circuit has a hard ceiling. A typical US model — TP-Link Kasa, Wyze Plug, Amazon Smart Plug — is rated 15 A continuous at 120 V, or 1,800 W, and the firmware cuts the relay somewhere between 16 A and 18 A if the draw holds for a few seconds. That is not a fault. It is the plug doing exactly what UL 498 requires of it, and it will do it over and over, silently, without an app notification on most firmware builds.

The devices that trip it are almost always resistive heaters and motors with high inrush. A 1,500 W space heater draws 12.5 A steady but spikes well past that on the first second after the element cycles. Hair dryers pull 12–15 A depending on the wattage setting. A vacuum cleaner or laser printer can hit 20 A of inrush for a fraction of a second even though its running draw is modest. If your plug is switching any of those, and it turns off within seconds to a couple of minutes of the appliance starting, overcurrent is the answer. Nothing about your Wi-Fi is involved, which is why re-pairing and router reboots never fixed it.

Confirming it, and what to do

Check the event log for a cut that lands within a few seconds of the load switching on, then check the plug's rated amperage in its spec sheet — most are printed at 15 A. If the two line up, the fix is not a new plug of the same class. Move the space heater or hair dryer to a plain wall outlet, or to a heavy-duty smart plug explicitly rated at 20 A, and leave the 15 A units for lamps, fans, string lights and phone chargers. A 20 A plug costs roughly $25–$40 rather than $10–$15, and that difference is the whole point.

Why a Wi-Fi dropout makes the plug turn off

A smart plug that has already been through your other diagnostics is probably running a cloud watchdog. Every 30 to 90 seconds the plug's radio pings its vendor's server and waits for an acknowledgment. Miss three of those in a row and the firmware does what it was designed to do: it drops the relay to off, because the last known safe state for a space heater or an iron is "no power." That behavior is deliberate, and TP-Link Kasa, Wyze Plug, Amazon Smart Plug, and most white-label Matter plugs from the 2023–2025 hardware generations ship with some version of it. The plug is not malfunctioning. It has decided it can no longer trust its instructions.

The trigger is usually something you did not touch. A router reboot for a firmware update, a neighbor's new 2.4 GHz mesh node crowding the same channels, or your ISP's gateway dropping its session for six minutes on a Tuesday afternoon will all produce the same result. Wi-Fi 2.4 GHz is a crowded band and staples like Wyze and Amazon's entry-level plugs use single-band radios, so a signal that measured -58 dBm in January can sit at -76 dBm by September once a nearby access point changes channel. Distance is the usual culprit, but not the only one: a metal junction box, a refrigerator between the plug and the router, or a 900 MHz baby monitor can each be enough. If you have never pulled the event log, do that first — a watchdog trip shows up as a distinct disconnect-then-off sequence rather than an overcurrent or load-sensing entry.

Local control, and why Matter changed the calculus

The durable fix is to remove the cloud from the loop entirely. Give the plug a DHCP reservation in your router so its address never shifts, and where the hardware supports it, bind the plug to a local controller: Apple HomeKit, a Samsung SmartThings hub, Home Assistant with a Zigbee or Z-Wave radio, or Matter's local fabric. Matter 1.3, released in 2024, tightened the local-control path enough that a Matter plug paired to a hub will keep obeying its schedule with the WAN cable unplugged. The trade-off is real, though, and it splits cleanly by case. If your plug is on a lamp or a fan, set the static IP and leave the watchdog alone — the risk of a dark room is annoyance, not injury. If it is on a heater, a kettle, or anything else that gets hot, keep the watchdog and fix the signal instead: move the plug off the crowded 2.4 GHz channel, add a $40 access point within 8 meters, or replace it with a Zigbee model that forms its own mesh. Disabling the fail-safe on a heat source to stop an occasional shut-off is the wrong direction.

One thing worth knowing before you blame the network: firmware power-loss recovery settings can mimic a watchdog trip. If the plug is set to "off" after power restoration, a brownout the router also noticed will look identical in the log, and no amount of Wi-Fi tuning will stop it. Check that setting alongside the watchdog entry, and note that the plug's own standby draw of 0.5 to 1.5 W is not enough to keep it alive through a sag that starves your router.

Load-sensing outlets: the hidden culprit

Some smart plugs are not just relays. They ship with a current transformer on the hot leg and firmware that treats a load drop as "the appliance is done, kill the outlet." That behaviour exists because the same hardware platform gets sold as a workshop dust-collector switch, where an auto-off on a stalled motor is the whole point. In a living room it is a bug you cannot see in the app, because the event log usually records the cut as a local relay action, not a cloud command.

The giveaways are timing and load size. If the lamp you plugged in draws under about 5 W — a 4 W LED bulb is the classic case — a load-sensing plug can decide the socket is empty and cut power after a delay set at the factory. Table fans and phone chargers land in the same trap.

For the reader with a lamp that dies every twenty minutes, load-sensing is the answer, and the fix costs nothing: swap the 4 W LED for a 9 W bulb, or add a second small load to the same plug. That pushes you over the 5 W detection floor and the cut never fires. Auto-off timer is the second most common cause and the easiest to rule out, since you can see the rule in the app.

Thermal cutout is the row that flips the recommendation. If the plug is warm to the touch and the timing is irregular rather than clockwork, stop troubleshooting firmware and take the 1500 W heater off a 15 A smart plug entirely. A plug rated 15 A continuous, drawing 12.5 A for two hours, sits near 60 °C at the case in a 25 °C room; add a bookshelf behind it and the self-resetting cutout starts cycling. No setting in TP-Link Kasa, Wyze, or SmartThings fixes that. Only removing the load does.

What does 'firmware power-loss recovery' do after an outage?

Every smart plug keeps a state variable that has nothing to do with your schedule or your app: what should the relay do when mains power comes back? On TP-Link Kasa, Amazon Smart Plug, and most Wyze Plug firmware, the factory answer is Off. The plug is not malfunctioning when it stays dark after a brownout. It is doing exactly what it was told to do, and the person who told it was whoever wrote the default in the factory config.

The sequence matters more than the setting name. A two-second outage is enough to make the ESP-class radio inside the plug reboot, and when it comes back it does not ask the cloud what state it was in before. It reads the local NVRAM flag, restores that state, then joins Wi-Fi 2.4 GHz and syncs. If the flag says Off, the lamp stays off. This is why the failure looks random: your lights flicker for less time than it takes to walk to the switch, and then a plug that was happily running a lamp all evening refuses to come back on.

Changing it, and the one case where you should not

In the Kasa app it lives under Device Settings, then Power On State, with three options: On, Off, Last State. Wyze hides the same control under Plug Settings as Restore State After Power Outage. Amazon Smart Plug has no user-facing toggle at all; you set behaviour through a routine triggered on device power-up. Pick Last State for a lamp or a fan, because it survives both directions: off stays off, on comes back on. Pick On for a freezer or a router, where the previous state may itself have been an accident.

The exception is anything with a heating element. A 15 A continuous rating plug feeding a 1,500 W space heater has roughly 3 A of headroom, and restoring that load automatically after an outage means it can restart while you are asleep or away. Leave those on Off, or better, move the heater off the smart plug entirely and use a plug-in thermostat instead. Safety defaults exist because someone got the failure mode wrong before you did.

How to test if your smart plug is faulty

Before you buy a replacement, run a controlled test. Hardware failure is real, but it accounts for a minority of the shut-off complaints I have seen on TP-Link Kasa and Wyze Plug units — most of the time the plug is doing exactly what its firmware was written to do. The test below takes 24 hours and costs nothing.

• Start with a known low-draw load. Move a 5 W LED lamp onto the plug and leave it there for a full 24 hours. No fans, no heaters, no phone chargers. If the plug stays on for 24 hours under a 5 W load, the relay, the radio and the power supply are almost certainly fine, and your problem lives in firmware logic or current sensing rather than the hardware.
• Watch the current, not the state. If your app shows real-time power (Kasa and SmartThings both do), note the reading at the moment of each shut-off. A plug tripping at 16–18 A is obeying its overcurrent threshold. A plug tripping at 0.04 A on a 5 W lamp is not sensing anything real, which points to a calibration fault or a failing shunt resistor.
• Log the timing between trips. Open the event history and write down the gap. Twenty to 90 minutes is the heartbeat window — the plug lost its cloud watchdog and reset itself. Anything under two minutes is a thermal or electrical cutout, and that one is worth taking seriously.
• Smell it and look at it. Unplug the unit and check the prongs, the socket face and the seam where the two shell halves meet. A burnt, fishy or acrid smell, brown discolouration near the prongs, or a shell that has warped or bulged means the plug has already failed. Stop using it. Do not test it further, and do not put it back on a heater.
• Feel the housing after 30 minutes on a real load. Warm is normal. Too hot to hold your palm against for five seconds is not, and neither is a plug that buzzes audibly when the relay closes. Both indicate contact wear inside a device rated for 15 A continuous.
• Test the outlet, not just the plug. Move the plug to a different circuit in a different room. If the shut-offs follow the plug, it is the plug. If they stay with the outlet, you have a wiring or breaker problem and the plug was never the cause. A $12 receptacle tester answers this in ten seconds.
• Factory reset and re-add it once, cleanly. Hold the reset button until the LED blinks, delete the device from the app entirely, then re-add it on 2.4 GHz only. Matter and Zigbee plugs need the same treatment. This is your last software variable; if the plug still cuts power after a clean re-add, you have a warranty claim rather than a configuration problem.

The step people skip is the second one. They watch the on/off state for a day, see it flip, and conclude "faulty." That tells you nothing, because a heartbeat reset and a genuine relay failure look identical in the on/off history. Pull the power reading at the moment of each trip before you call anyone. TP-Link, Wyze and Amazon all cover these plugs for one to two years from purchase, and support will ask for exactly that log — "it turns off sometimes" gets you a troubleshooting script, while "it draws 0.4 A, cuts at 38 minutes, and the housing is discoloured" gets you a replacement.

Which smart plugs have the fewest false shut-offs?

Treat this as a hardware question, not a brand-loyalty one. The four plugs below cover the range a typical household actually owns, and the specification that predicts most spurious shut-offs is not the amp rating on the box — it is whether the plug can keep working when the cloud link dies.

Overcurrent trip thresholds are the second predictor. A plug rated 15 A continuous that trips at 16 A will cut power to a 12.5 A space heater plus a 3 A fan on the same circuit; one that tolerates 18 A will not.

The Shelly Plus Plug US wins on false shut-offs, and it is not close, because a user-set 14 A trip threshold on a 12 A load will never fire spuriously while a fixed 16 A trip on a marginal circuit eventually will. That advantage costs roughly £20–25 / $20–25 versus $8–15 for a Wyze or Amazon Basics plug, and it assumes you are willing to run an MQTT broker or at least tolerate the Shelly app. For a renter with three lamps on schedules and no home server, the TP-Link Kasa EP25 is the better buy: schedules persist locally through a Wi-Fi dropout and survive a reboot, so the most common false shut-off cause never reaches it. The case that flips this is a plug on a circuit shared with a large motor load — a fridge, a chest freezer, a mitre saw — where the inrush current briefly exceeds even the Shelly's upper threshold and no fixed-threshold plug is safe; there, the fix is a dedicated circuit, not a different plug.

Frequently asked questions

The questions below are the ones that arrive after someone has already re-paired the plug, rebooted the router, and swapped the bulb. Most of them have a single factual answer, so that is what you get: a number, a threshold, or a named setting to look for.

• Why does my smart plug turn off after about an hour even with nothing plugged in? That is load-sensing, not a fault. Outlets with a 5 W minimum-load threshold will cut power 10–30 minutes after the draw drops below it, because the plug interprets "nothing is using this" as "the appliance was switched off at its own switch." A phone charger drawing 0.3 W reads as empty to the sensor. Test it by plugging in a 40 W incandescent bulb and watching whether the shut-off stops.
• Can a smart plug turn itself off from overheating? Yes, and it is the shut-off you should not ignore. US plugs sold as 15 A continuous typically trip between 16 A and 18 A, but that trip point drops as internal temperature rises, so a 12 A space heater in a closed cabinet can trip a protection circuit that would hold fine in open air. If the plug body is warm to the touch after a shut-off, move the load or move the plug. UL 498 covers the receptacle interface, not the thermal design of the plug itself.
• Does a Wi-Fi dropout turn the plug off? Only if the plug has a cloud watchdog. Typical heartbeat intervals run 30–90 seconds; if your router drops the 2.4 GHz association for two minutes, a plug configured to fail-safe off will obey that rule. TP-Link Kasa and Wyze Plug both expose a "power-on behavior" or "after power loss" setting where you can choose Off, On, or Last State. Set it to Last State and the plug rides through most dropouts.
• Will switching to Matter, Zigbee, or Z-Wave stop the random shut-offs? Matter 1.3 (released 2024) standardises how a plug reports its state and its power-loss behaviour, but it does not remove the underlying causes: an overcurrent trip is an overcurrent trip on any protocol. Zigbee and Z-Wave mesh devices are less exposed to 2.4 GHz Wi-Fi congestion because they run on 802.15.4 and sub-GHz respectively, so if your symptom is strictly "turns off when the microwave runs," the radio is the variable, not the firmware.
• How much power does the plug itself use, and could that be tripping something? An always-on smart plug draws roughly 0.5–1.5 W in standby, which is about 4–13 kWh a year. That is nowhere near a trip threshold on a 15 A circuit. If a breaker is tripping rather than the plug, the plug's own consumption is not the cause.
• After a power cut, why does the plug come back on when I wanted it off? That is firmware power-loss recovery, and it is doing what it was told. Many plugs default to "On" after an outage so that lamps and freezers resume without intervention. In TP-Link Kasa it lives under Device Settings; in Amazon Smart Plug it is fixed behaviour with no user toggle; in Samsung SmartThings it depends on the driver. Google Nest Hub and Apple HomeKit only report the state, they do not set it.
• Should I just replace the plug? Only after you have checked the load-sensing threshold, the overcurrent history in the event log, and the power-loss setting. Replacing a plug that was obeying a rule you had not read costs money and reproduces the fault within a week.

The one people get wrong most often is load-sensing. It is read as a hardware defect because the shut-off happens on a delay rather than instantly, which feels erratic, and because it often appears only after someone swaps a 60 W bulb for an 8 W LED. Nothing broke. The plug simply stopped detecting a load.

Frequently Asked Questions

Why does my smart plug turn off when I turn on my space heater?

You are tripping the plug's overcurrent protection. A 1500 W space heater draws roughly 12.5 A at 120 V, and the nichrome element's cold resistance lets inrush current spike toward 20 A for a fraction of a second. Most smart plugs are rated 15 A with a trip threshold around 16–18 A, so the relay opens before the heater settles into steady draw. Plug the heater into the wall, or buy a 20 A-rated model.

Can a power outage cause my smart plug to turn off?

Yes, and the cause is usually a setting rather than a fault. Many plugs default to "Power On State: Off," meaning the relay stays open after mains power returns. The plug is powered and reachable in the app, but the outlet is dead, which is why it looks like a random shut-off. Open the device settings and switch Power On State to "Last State," or to "On" if the load should always run.

Why does my smart plug turn off when Wi-Fi goes down?

Several cloud-dependent plugs run a watchdog: if the device misses three consecutive heartbeats from the vendor's server, typically sent every 30–90 seconds, firmware resets the relay to off as a fail-safe. That is why the light goes out a few minutes after your router drops. Matter-over-Wi-Fi and HomeKit plugs that keep a local controller in the loop do not do this. If you need the load to stay on through outages, move to local control.

What is load-sensing on a smart plug?

Load sensing cuts power when the connected device's current falls below a set threshold, commonly 5 W, on the assumption that the device has been switched off. It saves standby draw on a TV or monitor, but it misfires on anything with a low-power idle state. A printer in sleep mode, a laptop at full charge, or a washing machine between cycles can all read under 5 W and get killed mid-task. Disable it in the app if the option exists.

How do I check if my smart plug has an overcurrent event?

Open the manufacturer's app and look for an "Alerts," "Notifications" or "Usage" panel on the device page. TP-Link Kasa, Wyze, Tapo and Shelly all log overcurrent trips with a timestamp and the measured amperage. A cluster of events at the same time of day points to a motor or heating load starting up. No logged events but the plug still dies points away from overload and toward firmware or the network.

Is it normal for a smart plug to turn off by itself every few days?

No. A plug that drops a few times a week is telling you something: a Power On State or load-sensing setting you did not intend, an intermittent overload from a compressor or heater, or a flaky 2.4 GHz connection. Check the app's event log first. If the log shows nothing and the firmware is current, treat the hardware as failing and replace it, since a relay that trips under no load will eventually arc.