[martinald]

Probably they are estimates of not grid metered generation assets based on wind speed and solar production, at least in the UK nearly all solar is 'estimated' because it is not measured directly (apart from larger sites), at least in real time.

Rooftop solar for example just shows as a reduction in demand, not 'generation' per se.

[tialaramex]

This also true for private wind power. Britain has a measurable amount of hill top farms where it just makes good economic sense to install a wind turbine and get free electricity. But we don't meter it, it shows up in charts as an absence - on a windy afternoon maybe Britain is seemingly consuming 4GW less electricity than it "should be". If the wind drops that load reappears on the grid and must be handled by existing infrastructure.

None of this gear is suited to a black start. If you had total grid loss for a month you could doubtless rewire it to power the farm when it's windy despite no grid, maybe even run some battery storage for must-have services like a few lights so they keep working on still days but you could not start the grid from here.