How many times do you allow someone to not pay you but promises to, but seldom comes through? I did this guy a favor by putting the utilities in my name because he couldn’t get them in his name. Can I shut them off to force him to move out?
Stan,
I hate to say this but you have most likely just been hit by what causes most landlord horror stories…
First off, if your buyer can’t get the power on they aren’t the right type person to be selling to… a lesson learned. 
You agreed to allow the power to remain in your name and as the acting landlord in most states if you disconnect you will be doing what is referred to here as an eviction by force. (self eviction) This carries STIFF penalties and can quickly get you in hot water!
Your best action at this point is to start legal procedures TODAY and start the process of getting this deadbeat outa your property. If you post where you are from there are a great many people here that will likely be able to guide you in the right direction. If not visit your court house and ask them for the forms you need to file an eviction (or repossession if sold) and ask them what type of notice you need to give the tenant prior to filing… the courts cannot give legal advice but most will help get you pointed in the right direction.
Best wishes,
Ryan Needler