I don't think Van's publishes that information.
Assuming you have a 12V electrical system, then the light is recieving 12V (actually about 13.8V if the alternator is running).
If you have a 50Watt bulb installed, then at 13.8 V the light is drawing 50W/13.8V=3.6 Amps of current (+ losses to wiring). If you have a 100W bulb installed, it'll draw twice as much current at the same voltage.
You'll have to size your fuses and wiring to account for that plus a margin, plus the loss to the wiring. The Aeroelectric Connection by Bob Knuckolls is a good reference book for doing that.
Cheers,
Guy