To be fully off the grid, you’ll need to generate your own electricity (solar, wind, hydro, biofuel, diesel, etc.).
Once you’re generating your own electricity you’ll likely need a way to store that electricity until you’re ready to use it – so a battery system. New breeds of at home batteries like the Tesla Powerwall and Australian competitor AllGrid will make going off-grid even more accessible and affordable.
The alternative, ironically, is to set up a grid-connected solar system. This allows you to feed energy back into the grid when you’re generating a lot but not using much (like in the middle of the day when the sun’s shining but you’re stuck in your office). Don’t worry, as long as you’re producing more net energy than you’re consuming I’ll still consider you off-grid.
If you’re going to all this effort and expense to generate your own electricity, it makes sense to minimise the amount of energy you require. So energy efficient design, appliances and systems would be a wise investment.