"off the grid" is a bit open to interpretation. If you are thinking of it as a "lifestyle" or "permanent" or "semi-permanent" lack of grid based electricity, then solar seems the way to go.

OTOH, if you are thinking of some local problem that cuts the electricity, (think Katrina), but other energy sources are available, then I think generators are the way to go. If the CPAP is the only remaining item that needs electrical power, as others have pointed out, there are many small generators that will fit your need. If you have access to natural gas or propane, you should consider an automatic standby generator. It will more than cover the CPAP and provide power to some of the creature comforts, but most importantly the fridge, and safely storing food is a key thing. Between 10 to 15% of the folks (including me) in our neighborhood of 65 homes have installed them.