[toast0]

Here's my (unsolved) use case for a smart home: I've got three heat pumps and a whole house generator; if the generator is on, I don't want all three running at the same time (too much load), and generally, I'd like the set points adjusted, because I value saving fuel (the tank needs to last until the next filling, and I don't know how long the outage will be) over comfort. I've also got a hot water recirculator that I'd like to turn off when the well pump isn't powered (it's not on the same circuit as the house) or is otherwise not providing water pressure --- after a water leak, the previous recirculator burned its bearings moving air instead of water, and it was expensive to replace.

Also, I'd love to run the HVAC fans to equalize temperatures when some rooms are much cooler than others.

[chendragon]

This type of scenario shouldn't require "smart" home hardware - Traditionally situations like this were addressed by wired/wireless SCADA networks or BACnet or similar protocols.

The only issue is that these things are typically designed to be engineered along with the systems they control, and are difficult for the average user to implement or use.

[toast0]

The thing is, "smart" home hardware is a lot less expensive and more accessible than SCADA or BACnet. I can go out and buy any number of home thermostats, and some of them are even capable of properly supporting all the functions; unfortunately I ended up with the Nest, because it has the best support for enabling both auxiliary heat and emergency heat; but it doesn't have support for interfacing via LAN, and Google rescinded the APIs. Also, the physical interface is infuriating, but it's better than the awful honeywell touchscreen garbage the previous homeowner had installed.

[JshWright]

Assuming all those devices have means to communicate state and receive commands, that would be easy enough to do with Home Assistant.