The biggest time savings of 240 vs 120 V will come from the time to raise water to strike temperature. I can schedule my 120 V system to start heating the water early in the morning to be ready by the time I finish my coffee, so I don't even notice the extra time. The next biggest time savings would be when going from mash temperature to boil. My system takes about 30 minutes, but I am busy disposing of spent grain, cleaning the bag, etc. so I am not standing around waiting for a boil very often. If you do step mashes you may save 10 minutes or so with the higher voltage. Once you get to a boil you need to dial the power down anyway (I go to 60%), so it doesn't matter at that stage.