I am worried that there is not really a benefit of doing that, just more noise and energy consumption.
I think most wifi routers segregate the two networks, so they can’t see devices on eachothers network.
Someone will surely correct me if I’m wrong in this.
I’d say that depends. Some consumer routers may have guest network and client isolation on it though I doubt most do. Higher end routers support vlans can be configured that way and could be configured in many other wise such as talking to network 1 but not 2 or 3. For instance, I have IOT vlan allowed to connect to my server vlan for DNS since I self host DNS, but my general VLAN for personal trusted devices does can’t be accessed by IOT.
What benefit do you hope to get?
Are we talking main + guest network, or 2,4GHz + 5GHz, or something else?
Whether it has benefits is up to you, but from a technical perspective they’re as expensive as VLANs, so basically free. It’s the same receive and transmit radio, the only difference is that it broadcasts and responds to two network names at the same time. The maximum power consumption is the same: the max the radio will pull when at full load. The minimum power consumption has to be ever so slightly more since it needs to broadcast two network IDs, but those are measured in bytes and sent a couple times a second, it’s negligible compared to the cost of just running the radio.
I remember reading a few self hosters describing having a separate WiFi for IoT devices, on a dedicated router (opensense) so they can prevent these devices “calling home”. They are maybe other advantages like having different WiFi channels for these things
- They can’t potentially send my “real” WiFi credentials to someone who might exploit them.
- They can’t collect data on what is on my network or what I’m doing
- If one somehow has malware, they can’t harm most of my network or devices (there are well known exploits for cameras, for example)
- I can more easily limit the amount of bandwidth a poorly behaved device can use
