If a Zigbee device is plugged into the wall and stays powered, it is almost certainly already repeating the signal for everything around it. The Zigbee2MQTT documentation states that almost all AC powered devices will serve as a router. Battery powered devices generally do not repeat, because they sleep to save power and cannot relay traffic while asleep. So the twelve smart plugs you already own are, in all likelihood, already doing the job you were told to go and add.
The dividing line is the power source, not the price
Every device on the network sits on one side of a single line, and the line is drawn by how the device is powered.
A device connected to mains power can afford to keep its radio listening all the time. Because it is always awake, it can accept a message meant for something else and pass it along. That is what makes it a router in the network’s own terms, and it is why the Zigbee2MQTT documentation ties the role to AC power rather than to a device category.
A device running on batteries cannot do that. Keeping a radio listening continuously is the single most expensive thing a small battery device can do, so it sleeps by default and wakes on its own schedule to report. A device that is asleep most of the time cannot be relied on to relay anything, so it does not take that role.
This is why the distinction has nothing to do with how much the device cost or how recent it is. A cheap plug from years ago routes. An expensive battery sensor bought last month does not.
So yes, your plugs almost certainly count
The reader question this article exists for is some version of: people keep telling me to add repeaters, and I already have a dozen plugs, do those count?
They do. So do mains powered bulbs, and generally anything else on the network that draws power from the wall rather than a cell.
That reframes the problem usefully. If you already have a dozen mains powered devices, your issue is probably not the number of repeaters on the network. It is more likely to be where they are, whether there is more than one path between the far end of the house and the hub, or something else entirely. Before adding anything, it is worth confirming which layer is actually failing using the device, radio, router or cloud test.
The mains powered devices that are not repeaters
Here is the exception, and it is the part worth knowing because it is genuinely counterintuitive.
The Zigbee2MQTT documentation notes an exception to its own rule: most AC powered relays that do not require a neutral wire do not serve as routers. These are devices that sit permanently in a wall, wired to mains, that a reasonable person would assume are routing traffic like every other mains powered thing on the network. They are not.
The reason is a matter of how those particular devices manage the power available to them, and the practical consequence is what matters here: if the only mains powered device in a room is one of these, that room has no repeater in it despite appearances. A reader mapping out their own coverage by walking around and noting what is plugged in will count that device and be wrong.
Anything to do with the wiring itself, neutral wires, back boxes or switch installation is outside this article and outside this cluster entirely. The point here is only what that class of device does, and does not do, for your mesh.
Not all routers carry traffic equally well
The second thing the same documentation adds is that there are routers of mediocre quality, and that these can cause routing errors.
This is worth sitting with, because it changes the shape of the problem. The question is not only “do I have enough repeaters” but “are the ones I have carrying traffic reliably”. A device that technically takes the routing role but handles it poorly can be worse for the network than not having it there, because other devices will choose it as their path and then find that path unreliable.
There is no way to tell this from the outside by looking at the device. Where your hub software offers a network map or a route view, that is the place to look at which devices are actually being used as paths, and by how many others.
| Mains powered device | Battery powered device | |
|---|---|---|
| Radio listening continuously | Yes | No, sleeps between reports |
| Repeats traffic for others | Almost always | No |
| Known exception | Most no-neutral AC relays | None relevant |
| Counts toward your mesh coverage | Yes | No |
Why adding more of them does not always help
If repeaters are simply mains powered devices, it is tempting to conclude that scattering more around the house solves coverage. Sometimes it does. Often it does not, for a reason worth understanding.
What a mesh needs is more than one usable path between a distant device and the hub. Devices arranged in a single line down a hallway give you one path with several links in it, and a single failure anywhere along that line takes out everything beyond it. Adding a fourteenth device to the end of the same line does not create a second path.
The useful question is not how many mains powered devices you have. It is whether a device at the far end of the house has more than one way home. That distinction matters most after you have physically moved something, which is covered in rebuilding a mesh after moving the hub.
And if the whole network is unreliable rather than just its edges, coverage may not be the issue at all. Contention with your Wi-Fi is a common alternative explanation, covered in where Zigbee and Wi-Fi channels overlap. The general order for a device that used to work and now does not is in why a smart device starts going offline.
FAQ
Do smart bulbs repeat the signal?
Mains powered ones generally do, on the same basis as any other AC powered device. Whether a specific bulb does it well is a separate question, and one your hub’s network map is better placed to answer than a general rule.
Does a battery device ever act as a repeater?
Not in normal use. The role requires a radio that is listening continuously, which is what a battery device specifically avoids doing.
How can I tell which of my devices are actually being used as routes?
Some hub software shows a network map or route table listing which device each one connects through. Where it exists, that view answers the question directly. Where it does not, the power source rule is the best proxy available.
If a device is plugged in but switched off at the socket, does it still repeat?
No. The role depends on being powered and awake. A device cut off at the wall is not on the network at all, and anything that was routing through it has to find another path.
Should I leave mains powered devices plugged in even when I am not using them?
For the mesh’s sake, a powered device is more useful than an unpowered one. Whether that is worth it for any given device is your call, and depends on what else is relying on it as a path.
Sources referenced in this article
- Zigbee2MQTT, Improve network range and stability.
https://www.zigbee2mqtt.io/advanced/zigbee/02_improve_network_range_and_stability.html(accessed 2026-08-05). Source of: “Almost all AC powered devices will serve as a router (exceptions are most AC powered relays that do not require a neutral wire)” and the note that there are routers of mediocre quality which can cause routing errors.
This article describes general network behavior. Bloggent has not tested any of the devices mentioned and names no product as a recommendation.