Okay, but the "excess power in summer" does not magically materialize in winter. The current systems where it works like that are accounting trick meant to solar power industry.
In reality, we have no realistic mechanism for long-term energy storage on a grid scale - we barely start to breach scale where storage can handle daily fluctuations - like in California. And it's not free - it's being costly affair.
You're looking at this from a very different angle than I am, I think. While I acknowledge that at the system level we still have a way to go, we're already at the point where individual homeowners can sell power in summer and use that money to offset a significant portion of their winter costs - if they play their cards right. This won't solve all our global or national energy challenges, but it can make financial sense at the individual household level.
In reality, we have no realistic mechanism for long-term energy storage on a grid scale - we barely start to breach scale where storage can handle daily fluctuations - like in California. And it's not free - it's being costly affair.