It shouldn't be that complicated. The UK sells electricity to Ireland (and vice-versa?) in the same way that Belgium, France, the Netherlands, Denmark and Norway sell electricity to the UK, and vice-versa.

Don't tell me EirGrid's EWIC that comes onshore at Dublin and Greenlink at County Wexford are an "NI-shaped lump". They are sources of electricity for the whole island, when it's needed, just like the UK's interconnects with the continent.

https://en.wikipedia.org/wiki/List_of_high-voltage_transmiss...