They’re going days without burning fossil fuels by using high tech solar panels and windmills and such. What happens when they stop being made and they eventually break down? You’ll have to bootstrap tech again but without low-tech sources of concentrated energy. Electrified transport is great today, useless two hundred years ago.
Solar panels are somewhat high tech, but wind turbines are 17th century technology. The electric motor you need to attach to turn it into a generator is also pretty low tech. You can even use lead acid batteries to even out the power delivery, and those can be incredibly low tech and also highly recyclable.
Obviously you're not going to get to 100% in a week if you're rebuilding civilization from the ground up, but if you can retain some of the knowledge you can get a big step up and hopefully avoid some of the pitfalls that caused the downfall of society in the first place.
