This is a quickie: more of a tweet that exploded into a larger thought.
Last night during Black Mirror, I tweeted that post-apocalyptic dystopian future worlds (of which Black Mirror's was in the sense that all the people in it had lost their minds and were unable to function as a society) always bothered me in that most of them seemed to still have electricity.
I worked for a time in the energy industry, though Lord knows I was not particularly good at it. Now electricity is produced on-demand, which means that when you turn your TV on, you need generation happening somewhere to provide you that power. Power stations don't (for the most part) store any of their energy - it goes straight into the electricity grid and pops out at your plug socket. This is simplified* but essentially true. You can think of the National Grid as a system of pipes with water being pumped in one end (electricity generation from power stations) and being siphoned off at the household end (electricity demand for your TV). You have to keep 'pumping' energy in at one end for it to be available for all the millions of siphons in homes around the country. On top of that, you have to keep the frequency at a steady 50Hz - i.e. you have to generate at almost exactly the rate that it's being used - or everything goes bananas (technical term).
My overreaching point is this: if you don't have a massive, populated infrastructure of people running your power stations and grid, electricity simply won't work. So, when I see Will Smith watching a DVD in I am Legend, I wonder where his energy comes from? How does he pump petrol into his car? It makes me think there is a secret twist that actually the rest of the country is fine and Will was the last to know.
As a further point, it should remind us of how much we rely on one another. There really isn't much 'going it alone' as we rely on everyone else to do almost everything for us, without realising it. Be it generating energy, dealing with waste, preparing food, building all our stuff, we need each other.
This is handled very well in Gone - a book series in which every adult disappears and the kids left behind realise they not only don't know how to do anything - they can't do anything.
*Actualy, energy companies and the grid predict how much energy the country will need at any time in the day and attempt to match that demand GW for GW.