Upgrading Electrical Service Amperage During winter?

[Luke O'Connor]

I need to upgrade my electrical service to 200 amps in order to install central heat and air in one of the three units in my building. Only problem is I have two other sets of tenets in the building. Is it acceptable to turn off the power to the building for approximately 8 hours during the winter season? Obviously I would have to schedule it for a day where the weather is above freezing temperatures, but I am curious if this is illegal during some months in the state of Illinois? The other option I have is to find a contractor that is willing to install the central heat and air hardware and wait until the spring to hook it up to a power source.  Any suggestions or input is appreciated!