ZHA Channel 15 is over 99% utilized. Big lag. Please help!

I have well over 70 devices with ZHA using SkyConnect. I have like 6-7 light switches, 6-7 smart plugs and 5 smart outlets, as well 2 specialized Repeaters/Extenders. Basically at least 30 routers and I see some lag in my automations. I noticed it says the Zigbee channel 15 is over 99% used or something like that. What can I do??

I have bunch of other issues but this is so far the biggest one.

I also have Zigbee2MQTT running at the same time with over 40 devices there again with another coordinator SkyConnect, I on Chanel 11. But I don’t get this kind of message there about being overloaded. Only the ZHA.

First. This is not an overload message - only to be paid attention to IF you’re having trouble. It says nothing except the channel you’re using is relatively chatty.

You don’t see it on Z2M because this message is generated by ZHA.

If you’re having trouble with the setup. Then specifically troubleshot the issue. Of which this is only one tool to help figure out what’s up. Have you gone through the entire zigbee troubshooting section I the cookbook?

The Home Assistant Cookbook - Index (scroll down to Zigbee, start at the first entry - optimization)

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No, I have not read the cookbook yet, but thank you. I will read it and do my best to fix it. Any other information or tips are very welcome. Thank you all!

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Got that error also the other day but never again. Wouldn’t pay too much attention to that error when you get it once every some weeks and everything works fine.

That doesn’t mean there are any connection to the 2(statements) unless these automation in fact includes devices on the CH15, beside shuffling in routers does absolutely Not means you "improve your Network , as most of those seems to / might be “on” then “off” then “on” then “off” then “on” then “off” … get the Point ?, your Zigbee network will never ever “settle” … which you might understand after reading the Recommended Docs

Doesn’t ZHA have a built-in function to list congestion for each channel?

I’m pretty sure it does, and that the issue is caused by wifi (or some other 2.4ghz) interference. Read up on both and you’ll see which channel is the least congested and would cause optimal routing.

Yes it does, and it’s very handy to diagnose this type of problem:

  • Settings → Devices & Services → Zigbee
  • Click the three vertical dots next to the integration entity
  • Click download diagnostics
  • Search for “energy_scan”
"energy_scan": {
      "11": 60.0,
      "12": 38.8235294117647,
      "13": 55.294117647058826,
      "14": 54.11764705882353,
      "15": 70.58823529411765,
      "16": 70.58823529411765,
      "17": 69.41176470588235,
      "18": 75.29411764705883,
      "19": 68.23529411764706,
      "20": 48.23529411764706,
      "21": 67.05882352941177,
      "22": 85.88235294117646,
      "23": 85.88235294117646,
      "24": 63.529411764705884,
      "25": 52.94117647058823,
      "26": 81.17647058823529

Pick a channel that’s not too congested, you can play around with it to see which results work best or fix the problem.

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Thanks @CO_4X4 , I knew I wasn’t hallucinating.

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    "energy_scan": {
      "11": 99.66668541231483,
      "12": 7.659755505061292,
      "13": 25.74050169409602,
      "14": 80.38447947821754,
      "15": 99.50848219356503,
      "16": 92.0598007161209,
      "17": 68.14622793558128,
      "18": 98.78775542226437,
      "19": 99.27573563839312,
      "20": 99.17601569142556,
      "21": 95.69133648577223,
      "22": 98.62178092672917,
      "23": 98.43344238842926,
      "24": 88.70042934643088,
      "25": 95.12234809209261,
      "26": 87.33047519856483

How can I migrate now to channel 12 or 13 for example? I remember there is an experimental way to switch without having to pair all devices from 0 ? Thank you all for your answers!

Trust me it wont help you switching to channel 12/13
You should seriously first read up upon Zigbee networking And your WIFI

Which WIFI Channels do you use ?, And do you have a WIFI Mesh ?

When it comes to Your Zigbee Channels, they should Not overlap your WIFI Channels
When it Comes to your Zigbee “Routers/etc”, Don’t use Routers which you might turn On and Off, Each Time you turn Off a Router, you break the Route, and the Devices will have to find Another Route, And so your Devices will keep Re-Routing endlessly

You have to understand what and how your Zigbee Network work, you can’t just shuffle in Routers ( Which you turn on and off ) and think the more you got the better, you could/would in fact create the total opposite effect !

Seriously there is No easy way around this, you have to read up, and analyze your Network ( Not by changing Channels to 2 Channels you just discovered as the “lowest congested” , Tomorrow that may look different, judging by the way your Devices work, and Your Network Looks like


If you change the channel you do not have to re-pair, all your devices will remain paired but it may take a little while for them all to get on the new channel.


Most… Most of your devices.

Some devices aren’t exactly… Standards compliant? If you do a mass channel change I’d expect something to need to be re-paired. (mostly the older stuff but yeah don’t expect sunshine, unicorns and rainbows…)

Plan the channel change very carefully first.

I haven’t had anything fail on me yet, but of course that’s possible.

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Quite the opposite my friend. I’ve never had a channel change go 100% successfully.

The best one I’ve done half the network dropped and wouldn’t come back because one of the core routing devices refused to switch. Once I found it and rejoined everything else was great. But yeah channel changes are NOT a routine thing.

Yikes, that sounds no fun! I’ve changed mine two or three times without a hitch but I try to stick to mainstream product lines.

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And THATs the lesson. Your success will be tied to whatever devices are because how a device handles a channel change request is up to the device.

I don’t channel change except for a last resort… Unless the network was obviously setup on an overlapping Wi-Fi channel. In fact in those cases I look to see if the wifi channel can be moved first. Wi-Fi handles channel changes no problem.

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Considering that not too long ago a channel change required re-pairing all your devices, I’d take that as a win. It’s still 50% less devices you have to pair again at the end of the day :person_shrugging:

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What this chart shows is that your WiFi Channel 1 is in heavy use. Zigbee devices monitor channel quality and dynamically select the best available channel,