Landlord using Tennant's electricity. Whats the proper way?!

[Matt Romano]

I have a 2 family property with a detached 3 car garage that I'm going to start working on next week.  I will need to run electricity to the garage from either the 1st or 2nd floor tenants electrical service (just to work on the property, not actually putting electricity permanently in the garage).  And I'm just wondering how I should go about this.  Should I just mention something to either one of them that I'll be using some juice of theirs.  Or whats the right way to go about it? All thoughts appreciated!