In order to find the power (P) in Watt of a driver, we have to multiply its voltage (U) in Volt by its intensity (I) in Ampere:

P = U x I
W = V x A

Example :

Let’s take our DCC 15 – 350 SC (code: 1650425).
Output current = 350 mA = 0.35 A
Min. voltage = 27 V
Max. voltage = 42 V

So
Min. power = 27 x 0.35 = 9.5 W
Max. power = 42 x 0.35 = 14.7 W