I’m planning to build several WiFi connected devices for home automation: an AC remote control and air quality sensors. These devices would send data and be controlled through a local server. I’m considering two approaches: running custom software on a server PC (hardware to be determined) or integrating with Home Assistant’s protocols and purchasing their hardware. Would using Home Assistant be excessive for this use case?


I’ll also vote to reconsider WiFi. Home Assistant supports a variety of local mesh networks that by default can’t connect to the cloud and whose devices are cheaper and lower power.
I use all three of zwave, Zigbee, and thread; ha works with whatever you need.
Can you comment further on the three mesh networks rhat you use?
I only use zigbee, but would consider branching out
I got into each mesh technology for specific devices. Home Assistant supports them all and they seem to coexist just fine in my use case.
I have a small to medium setup with only a few simple automations and a focus on voice control and scheduling
Preference
But it also helps that my approach is generally switches and outlets. Hard-wired, predictable network, tend to be repeaters. I have comparatively fewer leaf nodes.
This approach also fits in with my biggest challenge. While my house is small, it’s an older one with dense materials that blocks a lot of radio signals. For example I have no cell phone reception inside yet strong signal just out any door. My focus on switches and outlets overcome this with a repeater in every room
So for example a few years back I got a z-wave IR blaster to control a mini-split AC because at the time I mostly used z-wave. I already had a z-wave light switch in the same room, acting as a repeater, so no worries about connectivity. Now I have both z-wave and Zigbee light switches in that room so expect both meshes to be strong for any future devices in that room