off the grid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adverb Without being connected to utility systems, such as those providing electricity and piped water.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective business Not using electricity from the public electrical supply system.
• adjective Not connected to a publicly available communication system, such as the world-wide web or a mobile telephone network.
• adjective idiomatic Isolated; in a remote location; in seclusion; not participating in some official process or system.
• adverb In or into a situation or place in which electricity from the public electricity system is not used.
• adverb idiomatic In or into a clandestine or isolated situation or place, especially one in which public communication is curtailed.
• adverb idiomatic Secretly; in a clandestine manner.