Centralized lighting control for an entire house is something you need to experience to understand the benefits of. The ability to have pre-programmed scenes, the ability to have lighting matched to outside color temperature is very nice. Integration of shades and lighting together, scheduling of lighting, scheduling of shades so you can automatically lower shades based on sun position. Plus not having multiple banks of switches all over - just have single keypads or touchpanels looks so much better than 6-gang (or bigger!) wallboxes.
Audio/video distribution throughout the house, so you can manage music, party scenes. Having a party and want the soccer game on every tv? Easy. Centralized rack with all of the audio/video equipment instead of having separate equipment in every room.
Climate control! When you have multiple air handlers, heaters, underfloor warming, and humidity control having the ability to manage all of them together is huge. Plus scheduling, plus occupancy sensors, plus duct control!
Not to mention control of all the related bits and pieces a large residence might have, like tv lifts, projector lifts, theatre screens, screen masking, garage doors, entry/exit doors, interior pneumatic doors, fireplaces, Tiki torches, pool control, spa control, water features, security cameras with PTZ, alarm interfaces, weather station, sprinkler control, power monitoring, etc, etc, etc . Anything that has ethernet, serial, IR, relay, BACnet, Modbus, TTL/IO, RF, or almost any other type of interface can be put into a system.
