An interesting question, just wanting to see if anyone knows. Like does it only last for how long he is in the sun or? 
 
Like if Supes was in the sun for 2 weeks, would it last for a whole 2 weeks out of the sun? Or how does it work?

@Wolfrazer: ithink he would just keep the power as long as he isnt near a red sun

...

Superman's cells act as an infinite capacity battery. Basically... let's say the sun can hit superman with 1000 watts of energy per hour. If he was in the sun for 24 hours he'd be charged with 24000 watts of energy.

This energy is constantly being spent at some minute amount all the time. Let's say 100 watts per hour. So after 24 hours he'd not have 24,000 watts of energy but 21,600 watts of energy. If he then suddenly teleported to some place where he didn't have light his battery would last for 9 days, if my math is right, if he didn't expend any energy from performing any powers.

Funny I should mention all this because we do have enough numbers in the new 52 and from reality to do these calculations to figure out about how much energy superman has...but i'll let someone else do that.

If he does use powers he uses up his energy quicker. It obviously depends on the power and duration and intensity how much energy it takes up.

As to how other light waves effect Kryptonians... that has changed with each depiction between the light waves "drain" him, nullified it, or simply doesn't give him new energy. "realistically" if red wave length drained/nullified yellow wave length light then it would take longer for the red light to do that since it would need to use be equal energy as the yellow light gave him and yellow light is higher energy so you'd need longer time or some sort of way to increase the exposure. ON the other hand You could also say that red light doesn't do any of that but rather catalyzes something in Kryptonian cells that seals away the expenditure of the yellow light energy. With the no new energy way you could also put forth the argument that he's getting energy but not at the same rate and simply can't replace the yellow light energy and eventually there isn't enough energy to manifest powers.

@Wolfrazer: What part of infinite capacity battery do you not understand?

As far as we know Superman can hold infinite charge. If he stayed in the sun 2 hours he would have 2000 watts of energy if he stayed in the sun 20 hours 20,000 watts...if he stayed in the sun for 20000 hours he'd have 20,000,000 watts of energy.

We don't know how much of that energy he can expend at a given time... For example he might be able to deliver a heat vision blast of 2000 watts of energy at max or he might be able to expend all the energy in his body at once.

There is nothing that says that Superman gets stronger when he runs down his energy. However, most things in the body do get stronger with use... however you can't get more powerful than infinite.

@Durakken:

Hulk agrees

@Wolfrazer said:

@Durakken: ....Oh wait sorry, was thinking something completely different then what you said. Ya I understand it, what I was thinking about was that the sundipping thing only lasts so long kinda like a temp power boost is what I was wondering.

No. it's not temporary.

Think of it more like Superman has an infinite stomach that he can fill with a ton of food, but eventually the energy you get from that food will run out.

When Superman is walking around on Earth, or even flying he can only take in so much "food" due to how things work... think him walking around as a normal person eating a healthy diet of foods

When he "sundips" he isn't getting a temporary boost, but it allows him to take in more energy or "food" do to how the universe works... think of this as a football player eating a large carbohydrate enriched dinner the night before the big game. Carbs give you a large amount of energy given equal sizes of a meal.

>.> Actually in some continuity blue light is more like a carb dinner...where as a sun dip is more like eating twice as much as you would normally.

It's not like the energy dissipates if you don't use it... it's all there. It's just stored in some way or used in ways you likely don't understand.

It doesn't bring up a really funny idea though... What is Superman started being Superman because if he didn't he'd keep on getting fatter and fatter ^.^