"Cheap storage" with the capacity for a week-long cloudy cold snap, epescially given how demanding EVs are, doesn't exist and will likely keep not existing for decades. So for now, if you want 24/7 electrity, your only option is a real large grid. Meanwhile gasoline cars just need a tank to store gas
I don't think you are talking about the same areas I'm talking about.
In areas where heating buildings interiors is a significant energy need, and has week long cold snaps, then there's extremely cheap storage in the form of therma storage, which combines very nicely with heat pumps, and it exists today. Bury insulated thermal sinks underground and a ton of summertime energy can be stored up seasonally.
However I'm not aware of any large populations of people that live in colder climates that do not yet have electricity and are looking to change their living standards in the coming decades.
