you will lose a tiny amount of power efficiency (probaby 2%) but aslong as your power price per KwH isn't stupid it wont make too much of a different.
Which 1000W did you order? i just replaced my old psu with a RM1000 and it made a huge difference

as an example, 2% * 1000W = 20W an hour

in a year you would be using an extra 175.KwH which even at $0.20 per KwH its only an extra cost of $35
so yes its $35 a month more expensive but your psu is under less stress and in theory should last longer