The nice thing is Sweden has lots of hydro, which works as natural long-term energy storage. Every bit of solar you generate means water is kept in the dam for use later in the year.
You also can't ignore wind power which should be part of any plan to "overbuild".
So why are the Swedes investing heavily in nuclear energy again, after nixing the nuclear exit they had on the books?
All of the discussions here conveniently ignore the existance of Wind. Which fortunately has higher yield in the months when there is less sun.