That is basically what happens in South Africa today. There are rolling blackouts and rich people with backup generators and batteries are unaffected. It's gotten to the point where richer cities (like Capetown) have their own power sources to mitigate the problem.

The current system is that everyone pays equally for X amount of stability, and for some people they don't get as much stability as they desire (eg. These people in Spain), whilst others pay more money and than they'd like when they would be fine with 5 minutes outages once a year.

That made sense before technology became available for everyone to make their own choice - but that is no longer the case.