See, that's one of the inconsistencies. What does red sunlight do to him? Yellow sunlight fuels his powers, so the longer he's in yellow sunlight, the stronger he gets (which raises the very real question of why Mala and Jax-Ur were able, within the space of a few days, to catch up to 30 years of Kansas sunlight). So does red sunlight actually leech the accumulated yellow sunlight out of his cells and actively reduce his powers, or is it just that the red sunlight means that there's no yellow sunlight, and therefore no recharge available? It seems that the red sun actively reduces his powers, otherwise red sunlight would put him in about the same position as he's in every night.
Plus, a "red sun" is still going to put some light out in the yellow spectrum, whereas Lightner's filter is going to remove all of the yellow. So, the sun in "Hereafter" is going to give him more strength than the filtered sunlight in "Solar Power". Very good point about the difference between filtered and natural red sunlight - this explains it even without giving Lightner more time to tinker with the intensity of the light (and giving more ammunition for criticizing the episode). Of course, I'm just defending this point, not the episode - I think both of the Luminus episodes are doubly disappointing because the framework could have been so solid, and they just fell flat.
Chris
I agree that some kind of explanation needs to be invented, because logically it absolutely should happen the way you describe (much like when the sun went out in Final Night*, way back when), but it's been pretty firmly established for ages that for whatever reason, red sun = immediate loss of powers.
*Yes, that was me admitting that I own that.