How to detect a power outage (2024)

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Many of us have set up one or more notifications for when, for example, movement is detected in our absence, the refrigerator is too warm, a water leak is detected, or smoke is present.

However, it is surprisingly difficult to detect when the power goes out. There still doesn’t seem to be an integrated feature to detect devices that go offline.

I have thought for a long time about how this problem could be solved. There must be a device that generates an event when the power goes out. Of course, this would have to be battery-operated and directly connected to the hub. At some point, I discovered the Woox Siren R7051, which meets these requirements.

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It has the following features:

  • Detection of the power source
  • Battery operated
  • Zigbee (not Wi-Fi/Cloud)
  • Acts as a router

@Mariano_Colmenarejo developed the driver for it and recently implemented support for power source detection. As soon as the device is disconnected from the power grid, it sends an event, and when it is reconnected, it does the same.

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But what if the power goes out and the hub and router are also down? Both devices must, of course, continue to be powered for at least five minutes. For this, there are small uninterruptible power supplies the size of power banks with multiple outputs. One of them is pictured here:

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My Aeotec SmartThings hub and the 4G router have been connected to such a device for some time now, and supposedly the battery should last for a day. However, I’ve only tested it for a few hours, but it seems to be true. I now have several of these to power the cameras.

Today, I tested the entire setup: Hub and router without a mains connection, then disconnected and reconnected the Woox Siren from the mains.

Here, you can see the delay between disconnection and notification and between reconnection and notification:

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At some point during the search for the solution, I forgot why I needed this. One use case is, for example, to automatically switch off all lights after a power outage.

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(When AC powered → Lights off)

TL;DR: to get a notification on your phone when there’s a blackout, all you need is this:

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And this:

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:+1: important when travelling away from home.

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Nice! And good to see something with current devices.

This has been a popular use case over the years and people have come up with multiple solutions for it. most commonly with one of the open/close sensors with dry contacts so that it will report closed when the power fails.

You can see other projects of this type on the “project_power“ quick browse list.

https://community.smartthings.com/tag/project_power

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The power source feature isn’t mentioned anywhere in the product description. I bet there are many other devices out there that emit an event when the power source changes. We should look more often at the logcat when we connect a new device.

Thanks for moving my post.

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An old mobile phone connected to a charger, which texts you if the power goes off.

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My (current) solution is the Zooz ZAC38 Range Extender. It has a battery that charges from the line to keep it alive if the power goes out–which sends an event to the hub and, assuming the hub & Internet are on a UPS and still operational, can send you a notification–or execute whatever else you want done in the event of a power failure.

After a particularly painful experience this year with needing a sump pump we didn’t have (our house, like all in the neighborhood was built with a sump hole, but no pump), this is our solution. The sump hole has been bone dry for several years, but this spring in New England there was a combination of freeze/thaw cycles, a Nor’Easter, and plenty of rain. (Luckily, I had a water detector and our daughter, who lives close by found the wet basement before mold began growing.)

So, the ZAC38 is plugged into the same outlet as the sump pump and, in conjunction with yet another water detector, should tell us if the pump ever fails again!

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I hope that in a few years we’ll have mini UPS with Matter/Thread support or at least Zigbee. An old thread from 2018:

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