energy performance on duo v1?

I think you aren't understanding what those specs mean. 1.5 amps is the most that the brick can draw from the main AC power, not the power use of the Duo. The 100-240 input voltage range, 50-60 hz is usual for a brick; it means that the same brick can used worldwide. (the brick converts whatever the AC voltage is to the 12 volts DC needed by the Duo).

Computing watts of power from the AC specs is a bit tricky, as it depends on the power factor. It is easier to do this from the output power specs. In the case of the Duo's brick, the output power rating is 60 watts (12 volts x 5 amps max output power). Again, this is the most it can supply. Similarly, your PC's power supply rating (often around 500 watts for a desktop) is the most it can supply, not the typical.

These power supply ratings are generally much higher than the average power use.

My UPS displays the actual power draw, if I remember correctly it is about 30-35 watts when the Duo is in use. That is also what the comparison charts show (http://www.readynas.com/wp-content/uplo ... n_Home.pdf). According to the comparison charts, the ultra 2 and ultra 2 plus also typically use 35 watts.