BACnet is often used in building automation, especially in HVAC systems. BACnet stands for Building Automation Control Network. It is a broad, semi-open protocol that can be used across different physical layers, but nowadays mainly over IP networks (BACnet/IP).

The BACnet protocol does not define its own commands, but it does define objects. These objects can contain measurement data or switching commands. This great flexibility makes it possible to "package" several other protocols into BACnet objects and use BACnet as a transport layer for other protocols. However, this also means that if two devices both have BACnet support, it does not necessarily mean that they can communicate with each other. They must also exchange the same communication objects.

Most professional HVAC systems and building management systems support BACnet. This protocol is hardly used in industrial automation. There are no known energy meters that support BACnet, but because many HVAC controls run via BACnet, it remains an important protocol.