Comment by WJW

Exactly as you'd expect: they make it possible to run the GPUs more hours in exchange for needing additional capital. Those batteries will have an upfront cost and will depreciate over time. You'll obviously also need more solar panels than before, which also further increases the upfront investment. Also note that now we're already straying away from the initial idea of "consuming free electricity from renewable overprovisioning". If you have solar panels and a battery, you can also just sell energy to the grid instead of trying to make last-gen GPUs profitable by reducing energy costs.

Again: it might work, if the math checks out for your specific source of secondhand GPUs and/or solar panels and/or batteries.