(The same question can apply to locations with 220/240V mains, if I am not mistaken.)
Frequently I see mixed ratings indicating that something is suitable for 110, 115, 118 or 120V (in the US). I've always referred to mains power as 120V but with the understanding that it varies because of:
- Different means of generation (number of phases, etc.)
- Line losses and imperfect conditions
When designing something, should one always test using the lowest expected voltage (110)? What reasons are there for the differences in mains voltage?