Oh wow, I didn't realize that! That's crazy, basically everyone that borders them are EU members. I was also under the impression (but haven't checked) that it was pretty easy to cross the swiss border both into and out of the EU.

Switzerland unilaterally got out of negotiations with the EU, which also dealt with energy grid coordination.

As such, as of now, the EU can shut down Switzerland without warning if the grid is overloaded and they need to avoid a blackout.