Same principle applies to most things. If electricity stops being readily available all the time, then you're introducing a new constraint that people have to optimize for. If that means they change their behavior, then they're doing something more expensive than whatever they were doing before, when they optimized without that constraint.
That extra cost generally isn't figured into the optimistic estimates of how cheap renewables are, but it's still a cost that society pays.
Building lots of charging stations at employer parking lots is also a new cost, that doesn't get counted against renewables.
