Required Notice to Tenant for Utility Maintenance - Illinois

[Phil Kagebein]

I have a 3-flat in Berwyn, IL and I'm required by the city to replace the electrical panels and some other misc. stuff. I had wanted to wait until all the tenants were moved out of the building to get the job done so I don't disturb them, but one isn't leaving easily. Since I need to get the repairs done with or without them there, what is the lead time required to deliver them a notice the electricity will be shut off? 

If I'm reading the Illinois Rental Property Utility Service Act correctly, it looks like 7 days is required: 

"This Section does not prohibit temporary utility shutoffs in cases of emergencies such as gas leaks or fire or, upon 7 days written notice to each affected tenant, temporary shutoffs required for building repairs or rehabilitation." 

Can anyone confirm that is correct? 

Also, would the written notice have to be certified mail, or can a posting on a door suffice. I'm living in the building, so it seems silly to mail something when I'm 10 feet away. 

Thanks in advance!