My old house has 4 air conds in bedrooms and 1 in living room. During night time, all 4 air conds in bedrooms will on together (all 1HP) and for the 10+ years we have not hit any problem.

How do we know if we should upgrade single phase to 3-phase? By counting the no. of airconds & water heater? don't think so right? is it troublesome to upgrade single phase to 3-phase later?