[outworlder]

Citation needed.

My power utility in the Bay Area powers residential customers 100% on renewable energy. Commercial and industrial do have fossil fuels still.

> maintain a duplicate fossil fuel backup system (fully maintained, staffed, and fueled) for those cold windless nights (so no longer cheaper)

Guess what, this is needed even in a world that only fossil fuels are used. Energy demand is variable and we need peaker plants on standby.

> deploy a storage system that can effectively time shift energy created by solar and wind across entire seasons (also not cheaper nor demonstrated with current battery technology)

We already need some storage in the current grid until said peaker plants come online. Maybe it's not 'cheaper' but it's been demonstrated. California alone has 2239MW of stored power at the moment I'm writing this (check the California ISO).

I'm not entirely sure you are familiar with how power grids work.