It already has become cheap. Well, at least if you are smart enough to do things yourself.
I built my own solar panel array and batteries that can power a whole house with
more kilowatts available than the basic Tesla pack specs for the same price. I didn't
need much more skill than assembling a 12 and up child's toy.
So basically I had 2.5kw in solar panels that were relatively
small in their footprint and could keep my 15kw of batteries charged
far beyond the daily appliance use requirements without a problem.
The price here is only talking about a battery box lol. No thanks!
Even some of the poor have managed to bring solar and batteries
into their life. Affordable for middle class? Or better-comprehended
by the middle class? Which is it gonna be for you? It all depends on
what you feel is most urgent to live for. The more you are prepared, the better.