If we're to believe the pre-release hype, Fermi will be the fastest single-GPU videocard on the planet when it ships, leapfrogging ahead of ATI's HD 5870. But all that power is going to come at a cost, including a beefy 600W power supply, according to reports from CeBIT.
We've often seen inflated power supply requirements, as GPU vendors have to take into account lower quality units and how the all-important +12V rail distributes amps. But in this case, it looks like Nvidia's talking about a 600W PSU "with a minimum 12V current rating fo 42A," which would indicate a higher quality unit.
By comparison, AMD's dual-GPU 5970 requires a 650W power supply and is rated at 294W TDP. In single GPU territory, AMD's HD 5870 requires a 500W PSU, or 100W less than Fermi.