"So what is an acceptible voltage for a 120v device?
A toster would work ok. shorter or longer life?
A computer, shorter or longer?
would some devices have tollerance of some range. like (+)(-) 5% or something?"

Being that a toaster is juste a heated element (like a lightbulb) I would say higher voltage would shorten it's life but how much I don't know. It would make toast faster [Linked Image] As for computers, they use switching power supplies and they would just alter thier duty cycle to compensate for voltage changes, which they are designed for anyway. So, I don't think it will make much difference there. As to acceptable variations I think UL suggests(requires?) something like 108 to 132 volts. Could be misttaken though.