The Lutron "Maestro C•L" dimmer has different wattage ratings depending on the type(s) of bulbs being controlled. Its an electronic dimmer.
Specifically, when 100% incandescent or halogen it can handle 600 W, but when 100% LED or CFL only 150 W, with a gradual variation between these extremes for mixed bulb types.
Info from the specification sheet:
(The wattage capability also varies based on the # of "sides removed" though I can't see in the docs what that means.)
What is the reason for the degraded wattage capability when running LED bulbs?
And is this variation in wattage capability typical of this sort of dimmer?