In my house? Pretty much never. We have solar as well as a grid connection and can connect a generator as well.

In fact, I even have a second stand alone portable solar system that we take camping. It's not powerful enough to heat a house... but it is powerful enough for pretty much everything else. And I can heat my house with a fire if it came to that.

Redundancy is the name of the game if you're worried about reliability.

afaik power never really goes out in western europe unless something happens to the infrastructure (e.g. lightning strike or tree falling on a power line), what instead happens when we run out of generation capacity is that prices skyrocket.