Those are the most bullshit emtpy threats I've heard in a long time. "Finding out your IP" doesn't mean anything, because he'll only get the public IP supplied by your ISP. It will change after 24-48 hours. If he'd be able to find out your public IP, he'd be able to look at your network from the outside, finding... nothing.
If he somehow (and I cannot stress this enough, it'd be a miracle) was able to get access to your network, he might be able to do some harm if he's allowed to access your machines and he might be able to read and/or delete personal data. He still wouldn't be able to shut down your power, since it's not controlled by anything on your network. He might be able to turn on and off some smart lamps you might have installed, but that's about the extend of "turning off your power".
Like it was mentioned, the only way he'd actually be able to turn off anything is by accessing the networks of your power supplier. But seeing that they're a company that most likely hasn't been living under a rock for the past 20-30 years, they'd probably just laugh anything the guy could try off. If they'd even notice his pathetic attempts.
It's bullshit, he has no way of doing anything. Don't click on any links he sends you (although even then he most likely wouldn't be able to do anything, if you don't continue to make dumb mistakes). Tell him I said he's an idiot and make fun of him and then find new people to hang out with on discord.