[ben_w]

> It's ridiculously cost ineffective to charge a battery in July only to discharge it in December

Indeed.

This is why the cheapest solutions in most places are a mix of a mere few days off storage plus a target production level that is a little higher than you need on an average day in winter.

While this doesn't work above the arctic circle (you could do it with a power line somewhere sunnier or a synthetic fuel, and possibly also geothermal or nuclear etc., devil is in the details for all options) overproduction + 35-90 hours of batteries is sufficient for most people and places:

https://tonyseba.com/wp-content/uploads/2020/11/RethinkingEn...