You asked how long "all my life" I've spent only partially reliant on the power grid is, and someone else has provided you some context (that I actually mean all my life, which you can probably infer to be longer than two decades at least).
As to the second half of your original question, solar power is not the only kind of backup power that exists.
As to the second half of your original question, solar power is not the only kind of backup power that exists.