I am considering all options before diving into my first Home Assistant setup.
Right now I am considering Wifi, Zigbee and Z-Wave. The main and almost only concern regarding Wifi is the amount of devices that can be used in parallel.
Apart from say 10 heavy load devices (cameras, security components) I could easily imagine small devices like automated power outlets, light switches, shades, thermostats etc. to add up to > 100 devices.
Although theoretically possible, most router manufacturers recommend no more than 20 parallel devices to prevent traffic from killing your bandwidth.
Has somebody got experience with large scale wifi installations?
With WiFi it comes down to infrastructure. I suspect your local hospital has far more than 20 devices attached to its WiFi at any given time without issue, for example.
Just need to research it and factor the infrastructure in to the cost of the project, same as anything else.
I have over a hundred wifi devices spread over 4 Ubiqiti AP lite access points (far from evenly). All on the 2.4GHz band. I use the 5GHz band for my laptop and mobiles, so no issues with bandwidth.
Your typical teleco provided or consumer AP is not going to do it for you. Even the cisco made internet router / AP choked at about 12 devices. So start with at good one, there are a few out there. I work in IT and have managed very large scale deployments globally. My personal choice for home is Ubiquity. I started with just one AP and got it up to 75 devices before adding another AP. General good practice on APs is really about 35 devices for moderate use devices. For home automation most devices are very low bandwidth users so you can have quite a few on a good AP.
All my notebooks, streaming, video is on 5G. Lots of bandwidth there. The majority of the smart devices are on the 2.4G and though not as much bandwidth it is fine for smart switches, lights, etc.
If you decide on Ubiquiti, Home assistant has an add on that takes all of 10 seconds to install on your Pi.
Your cameras should not be on a wireless connection, and your security devices should not be on Wifi OR any 2.4GHz wireless protocol, as it is trivially easy to jam.
Bandwidth yes, but not for IOT devices (especially with a local connection), since something like a smart plug or temp sensor uses less than a kilobit per second, the problem is simultaneous connections to the wireless radio. Some IOT devices are offline and only connect when they need, like z-wave, and some wifi devices like a Shelly door sensor. But most wifi devices need a constant radio connection, and cheap network infrastructure does not do well.
I have an Ubiquity AC-LR which has a high gain antenna and is rated to support 250 simultaneous connections over both frequencies, although at that level they will not have fast or low latency connections.
You should, under ideal circumstances, have multiple access points, distributed both by location and bandwidth use, so that every device has good signal strength, high speed devices have enough bandwidth, and no access point will have its radio saturated with too many clients.
I have a single access point, but I know I need 3 for good coverage. Also the one I have now is sharing an uplink with a switch that is connected to a high bandwidth wired device, and that can slow down wireless devices.
Once I get a few more wires run, and add 2 more access points, I should be able to handle over 300 wifi devices all with low latency connections, and have no choke points for bandwidth, since there will be enough radio connections for all high bandwidth devices to operate simultaneously.
I have over a 100 Wifi devices, no problem at all. I don’t have Wifi camera’s though (except an esp32 cam with esphome on it) One router flashed with openwrt, 2 old routers used as access point (dd-wrt), 2 cheap Aliexpress access points.