3 Amps. When you rent a cage at a data center you are allocated a space and then a single circuit, usually 120 Volts, 20 Amps (so ~2400w max for that circuit). Of course, people do specify extra circuits with capabilities, like a 30A 208 Volts 3-phase to run high-draw devices like blade enclosures.3a power is what in terms of watts in PSU terms?
The cage tenant is responsible for supplying its own PDU (power distribution unit) and will be expected to keep it below the limit, and if you get a "smart" PDU, each outlet is monitored and controlled separately.
If you are given a 3 Amp allocation in the cage you are expected to keep it below, oh, ~360 watts.