If a 2500W PS is connected to a 220V connection, it will operate at maximum capacity.
cat6500B (enable) sh environment power
PS1 Capacity: 2331.00 Watts (55.50 Amps @42V)<<--
If it is connected to a 110V it would be half. So do the above command if running CAT OS. If running IOS, issue a sh power.