Thanks to climate change, this is probably not going to continue to be a 1 in 20 year load. Expect this to be more and more frequent over the coming years. Might be an every year and/or multiple times a year thing within the next decade or two.

I've read some predictions that suggest these heat waves becoming a regular thing could happen within the next five years, but I'm sticking with more conservative predictions.

Do you really need to pay for house wiring that can handle a once every 20 year load? Pretty sure you would change your tune when the wiring melts in one of your walls.

That's the real question. Even 1 in 10 year load, do you build for it or just live with it? It's just a $ decision.

Grid yes , maybe not the power plants themselves. Typically in robust networks you have good interconnects to neighbours you can purchase power from .

Also robust grid which enables selling back to the grid would have helped, such extreme hot weather goes in hand with solar generation