I'm more or less a german 'prepper', but this article doesnt really tell good reasons to prep. I personally think everyone should have food and water stored for atleast 14 days(which is also something the government recommends), because natural disasters or other disasters can still hit you, even when your country is stable.

As for the stability of the country: In Germany we sadly have a very misguided energy policy. We are essentially building back more than we are building up. We are closing down or planning on closing down nuclear and coal, yet we are not even building enough renewable energy sources to cover the needed demand. Our energy storage capabilites are not enough. We dont have all the powerlines build or even planned that could transport the offshore wind park energy into the deeper mainland. We will be missing multiple gigawatthours in the future. As it seems Germany is just planning on importing the difference from countries around us.
Sadly this makes not only the german grid unstable, but the whole european grid. We already had 2 close calls in the european grid this year, which luckily were resolved by the engineers. We are going closer and closer to an actual blackout, and this could cascade into larger areas of europe, since the grid is interconnected. A real blackout, and not just a temporary power out will take 10 to 14 days to resolve in optimistic calculations. If there are problems getting the grid started again this could well take longer.
No power means: No running water after 1 day at best, no supermarkets, no fridges, no heating, no cooking on usual stoves, no phone calls, no internet, no fuel stations, etc.
Of course no phone calls means you cant call the police, which is very practial for criminal gangs. No phone calls also means you cant call the firefighters, and if there is no running water whatsoever they will have a problem quickly as well.
Streets will clog up because of accidents and cars running out of gasoline, blocking of the supply ways for hospitals. So they will also get into troube relatively fast.

I could go on but I think you get the gist of it. A blackout would be like a temporary 'collapse' because the whole modern way of living is just suddenly halted, with people not being perpared for that. Now I think this scenario would be less drastic if people were aware of the danger and prepared accordingly. If everyone has some food and water then the shortages wont be as drastic immediately.

Now I cant predict the exact date when this will happen, but I think that in the 3 years this will happen, unless we radically change our energy policy. Janurary next year will be interesting as there are some powerplants permanently going offline, which will increase the instability. You just need to have a bad day with not enough or too much wind and little sun, which is likely in the winter, and then you already have it. Add to that an increased demand though heating, light, etc, and the odds start looking worse.

Some interesting links for the topic:
https://www.smard.de/en (An official realtime tracker that shows how much energy is being produced by what source)

https://www.bundesrechnungshof.de/de/veroeffentlichungen/pro... (This one is in german, but here you can see some official data on the whole grid situation and its future.)