Self-sufficiency seems to be relative to a host of circumstances.
When we lived in the country (our 15 years of pleasurable – even festive – life simplification), a month without the grid was thinkable and doable without tremendous effort. In a sense, our lifestyle kept us naturally prepared. Water that could be rendered potable was plentiful, as was our storage space, and the ability to cook outside with fire (we always had several cords of spit hardwood for winter, and there was always enough left to cook with in the other seasons).
Now we live in a small apartment in a small-city urban environment. That choice makes us more grid-dependent, and sets certain limits on how prepared we can be, relative to our former life. Also, now in our mid-70s with medical issues, camping out with backpacks and maps is a non-starter. Water might be the main issue. We can store canned goods and dried goods that do not require water for preparing. A month may be a bit much to hope for, but a couple weeks seems doable for sure. We keep a good supply of batteries for lanterns and electric candles. Any kind of fire (e.g. a charcoal grill) is forbidden under the terms of our lease – but a small gas grill would undoubtedly be overlooked in the kind of situation we’re talking about.
None of this detracts from Julia ‘s points at all; on the contrary, they are appreciated.