Messing with the air conditioning can affect a lot more than just the people who have the vulnerable IoT air conditioner, if it manages to bring the grid down.

Messing with the air conditioning can affect a lot more than just the people who have the vulnerable IoT air conditioner, if it manages to bring the grid down. The grid is able to cope with fluctuations in demand, but that's a totally different ballgame than switching massive loads on and off, synchronized to within something like 20 milliseconds (a single 50 Hz cycle), in a controlled, intentional and malicious way - and potentially worse, the attacker could observe the grid and react to the countermeasures (e.g. to detect how quickly the grid reacts, and trigger oscillations in some system never designed to deal with something like that).