It strikes me that this is very similar to the NBN (broadband network) problem. There is a widely deployed network of old technology that is no longer worth inv

It strikes me that this is very similar to the NBN (broadband network) problem. There is a widely deployed network of old technology that is no longer worth investing in (copper in the NBN case / coal plants) and newer technology (solar + storage) that is still a little pricey (storage) and not widely enough deployed. Which means you need to manage a transition so it's not too painful. A first random guess - One way might be to allow a few coal plants to go bust, and enact "load shedding" (turning off areas of the grid during times of low demand). Within a year or so, enough places will have batteries that you're load shedding less often. If the government purchases the coal plants when they go bust (at a steep discount), they can then stagger the shutdowns enough that load-shedding is controlled. But it doesn't seem sensible to force it to be economic to run the coal plant full-time. Surely that just drags out the transition, and suppresses the demand for storage that we're hoping will be the solution?