Wiktionary
a. 1 (context of a home, business, or the occupants thereof English) Not using electricity from the public electrical supply system. 2 Not connected to a publicly available communication system, such as the world-wide web or a mobile telephone network. 3 (context idiomatic English) isolate; in a remote location; in seclusion; not participating in some official process or system. adv. 1 In or into a situation or place in which electricity from the public electricity system is not used. 2 (context idiomatic English) In or into a clandestine or isolated situation or place, especially one in which public communication is curtailed. 3 (context idiomatic English) secretly; in a clandestine manner.
Wikipedia
Off-the-grid is a term to describe housing not connected to public utilities.
Off the grid may also refer to:
Off the Grid is a mobile food truck festival in the San Francisco Bay Area of California, USA.