The Russian "soldiers" can loot food, fuel, and ammo. Maybe not much, and maybe they die in the process of trying. And the generals will try to make sure they at least get ammo, because Russian soldiers surrendering = trip out of a window for leadership. Food and fuel, not so much, and they've already pulled out Soviet-era food.
The Muscovites and St. Petersburg types can buy food on the black market (but not all can), but can't loot electricity, or buy it on the black market.
And the panic buying kicks in and the black-market kicks in and reduces the government's ability to move stuff around because the wealthy are buying it up.
That could very well explain why they are hitting power stations/substations in cities that ostensibly have small-ish populations (hundreds of thousands) but I bet if one digs, they act as transport hubs of some kind.
Thanks, some interesting stuff to ponder, would be curious to look at the cities whose power grids were knocked offline, since everybody is focusing on oil & gas.