The power-companies-are-screwed story is a bit oversold. The cheapest solar power comes from large solar farms, exactly the sort of thing power companies themselves build and operate. Smaller distributed solar units are a big financial winner in the following circumstances:
- If retail electricity prices are moderate/high and excess solar power generation gets a net metering credit. I don't think that this will remain common as solar penetration increases, but some early adopters in different regions will be able to take advantage.
- If the electrical companies invested too much in transmission and distribution infrastructure and are now making up for it with high prices per kilowatt hour. This describes the Australian rooftop solar boom and at least parts of California. Note that this can be a financial winner even without retail-priced net metering; you're just thrifting on how much overpriced electricity you buy from the power company.
- If the location is far from the existing grid and you're expected to pay to build the intervening connection yourself. Solar plus batteries, even with today's relatively high battery prices, can beat the cost of building that connection.
Mostly I expect power companies to survive the rise of solar power just fine. Most solar generation will come from large facilities owned by large companies, not household rooftop units. The over-representation of small rooftop solar units in Germany has contributed to the high cost of their energy transition. I see the German policy decisions favoring small solar units as a carrot used to ensure broad population support for solar power. Maybe it was politically necessary. But the generating costs would be lower had they favored fewer, larger installations.