(27.67% - 22.74%) / ~3 years = 1.6% per year, a little larger of a rate than 0.3%/quarter, though, also it appears to have accelerated.

part of this is that since renewable is free to run while fossil fuel isn't, renewable mostly runs at 100% availability with fossil fuel making up the gaps.

100% availablility? Except for nighttime, or when the wind goes down?

possibly poorly phrased, but what I meant is that you pretty much never turn your solar panel off, but if it is a sunny or windy day you will stop pumping natural gas into a gas generator.

Pushing electricity onto the grid does come with a cost though and if the electricity is pushed onto the grid at a time when it is not needed, you need to deal with it somehow. In some jurisdictions (parts of Australia) they cut you off from the grid if there is an overproduction of solar.

How do you reconcile that with the article's statement that renewable generation went from 22.7% in 2020 to 27.7% today? Five percent in 3 years seems quite significant.