Anything over 3/4" seems to take a long time with one of these torches. I've used a small patch of fiberglass insulation to insulate the other side of the copper while heating to help the copper retain heat on larger pipe. If it's all you've got, you can probably do 1" fine. Bigger will be tough.
Unless I have to carry it up 3 or 4 flights of steps, I'll bring an acetylene torch for anything 1" or bigger.