DC grid conversion is much more expensive than even a large transformer. Cold (aka "black") start is not a common occurrence. Vacuum cleaners are not much of a

DC grid conversion is much more expensive than even a large transformer. Cold (aka "black") start is not a common occurrence. Vacuum cleaners are not much of an issue. Industrial consumers are usually mandated to sort out their apparent power factor so it's not too weird for the grid. What does matter sometimes is phase/frequency trips. The grid frequency is an important coordination mechanism between generators. When it gets distorted by loads coming on/offline, sometimes this can cause other generators to trip out at 59/61Hz, and then you get the Spain blackout situation. Batteries could solve this but the software/regulatory framework isn't entirely there yet. See e.g. the UK market for "fast frequency response".