It's also important to point out the grid is archaic in many places and the knowledge isn't omnicompetent across the system. In the US, we have three major grids which are also connected to Canada's (which I can't speak too). [0] From my understanding, with an amateur interest, we know a lot about where those major grids connect but very little about the distributed nodes that make up the network; The Northeast Power Blackout of 2003 is a really great example of this. [1] Essentially, there was a grid failure that occurred in Ohio which overlapped into the other sections of the grid. In short, a wire contacted with a tree in Ohio which caused a cascading failure to NYC.
So, let's now bring IoT into the mix. You and I have smart houses, with smart solar tiles. John attacks our tiles plus all our neighbors and directs a major electrical spike towards our local substation. Now it's a physics question, where are all those joules of energy going? It's a heat problem and right now there is no way to dissipate that heat from the system which will melt our substation. Let's say our neighborhood is between several other neighborhoods and the main power station, we just killed a node and guess who else doesn't have access to power because they don't have tiles like we do.
That's the basic concept on why security and authenticity are important in relation to the energy grid. It would be nice if there was an effective way to dissipate an "electrical DDoS"? I'm not sure if it's called something else. If you're interested in the energy dissipation within the energy grid, this is a great question on SE. [2]
That all said, is also a major reason why the government is consistently freaking out about our power grid being hacked.
[0] https://en.wikipedia.org/wiki/Continental_U.S._power_transmi...
[1] https://en.wikipedia.org/wiki/Northeast_blackout_of_2003
[2] https://electronics.stackexchange.com/questions/117437/what-...