True; but in my experience having lived in apartments with balcony and in houses, I found the need for power in an apartment much less than in a house. First, apartments (at least the ones I lived in) seem to retain heat better---the thermal mass of the building around the apartment I think. Second, in an apartment I didn't need to worry about pumping out a basement, but I do in my house--the sump pump (a 3/4 HP electrical device by itself, which draws 7 amps).

That pretty much leaves lighting and cooking (assume electrical stove, not gas). Lighting, in this day of efficient battery powered lights should not be a problem. As for cooking, you probably could use a small propane powered stove on the balcony without anyone complaining, or even noticing. (Don't use it inside).

That leaves a need to recharge things like your cell phone, etc., which does not draw much power. Possibly battery powered rechargers could be a solution.

If there is a critical (e.g. medical) device that you need powered, then I think a bug out plan is needed.

People lived, and still live, without electrical power. Think of the apartment as a "cave."

For me, the critical problem of the apartment is the elevator (if it has one). That can trap you, and least make access really difficult to impossible. But a generator on the balcony is not going to fix that.