It's based on the equivalent in fluorescent, not incandescent. Hence it's the actual wattage if the light is fluorescent, as these are.
so a 100w (using 26w of power, or whatever it is, somewhere around there...) would be a 26w for the purposes of wpg?
do you know of any place I could find more about this? it seems pretty interesting that we're using the actual electricity and not "effective light" (my term), it does make some sense, but i'm also hard-headed, lol.
i think i just need to read more about it. in my google searches, i've only found a few articles and none seem clear about the "why"...