Shutting down the Powergrid "PERMENANTLY" may have work, otherwise it's more or less inconvenience than actual need. And do you even think the Military of Ukraine was hooked up on the same Powergrid? LOL, maybe in Iran they did, I have been to Ukraine in April, I can tell you that they don't. Actually, I have been to many Military installation, US, UK, Germany, even Iraq, they have a different grid than Civilian, and most military are all-day all-weather force anyway, which mean even if the entire Powergrid system was down, it does not hamper the force ability to conduct operation. Which mean shutting down the civilian grid for 3 days does not do anything for the military, all you did is to make the poor soul in Kyiv or Lviv can't download the latest Netflix episode from the internet.
And dude, Ukraine is at war, a war that they didn't ask for, do you think bombing them will zap their morale?? If so they would have already given up the fight already, you say it like Russia did not target civilian infrastructure before September. What make them fight is to protect their homeland, and what Russia is doing is to try and destroy it, in fact, what Russia is doing is fanning the hate in Ukraine, more Ukrainian join the fight, they just reported that they have recruited twice as many as new recruit than previous 6 months and they aren't short of manpower, all thanks to this. And It didn't work on the Londoner back in WW2, what make you think it work in Ukraine now?
Again, you want to win a war, that can only be done by killing your enemy fighting men, not killing civilian, if you don't understand that principal of war and think it would have made a different, then all I can say is you are extremely naive. You want to know how to zap Ukrainian morale? Look at what the Ukrainian done to the Russian. Battlefield loses zap both strength and morale of the enemy force, you don't demoralise your enemy by hitting their civilian, you do that by denying their attack and counter-attacking them, you destroy their tempo, then morale will follow, that's why Russian force morale is rock bottom now, how many Russian civilian has been killed by the Ukrainian? How many Russian City got plunged into darkness by Ukrainian missile strike??. That's warfighting 101.