Let's say i have 2 powersets, one during day, one during night. What would that give me back in refresh? 1 like in involuntarily change?
Under that power it doesn't "give any points back" at all, at least not in the sense that involuntary change does. Instead, it basically gives you the ability to swap one set of pre-defined powers for another set of predefined powers with the same or lower total refresh. The power to do this costs -1 refresh over the cost of the set(s).
Here's an example of a "Dr. Jekyll" character that's a Wizard normally, but can turn into a monstrous "Mr. Hyde":
-1 The Sight
-0 Soulgaze
-0 Wizard's Constitution
-7 Wizard/Warg Powers (-6 refresh worth of powers)
Slot 1: Dr. Jekyll Powers
-3 Evocation (spirit, fire, earth, +1 spirit control)
-3 Thaumaturgy (+1 craft strength)
Slot 2: Mr. Hyde Powers
-2 Inhuman Strength
-2 Inhuman Speed
-1 Claws
-1 Echoes of the Beast
-8 Total refresh cost
So this character would have The Sight, Soulgaze, and Wizard's Constitution permanently, but has spellcasting only in "Dr. Jekyll" mode and the physical powers only in "Mr. Hyde" mode. Switching between the two would take a full action, and in this case would be at will, though an appropriate aspect might be used to compel an involuntary change. (The Involuntary Change refund listed under Beast Change doesn't apply, since you have access to all refresh worth of powers all of the time.)
I'm not entirely convinced this custom power is balanced (ie, for -1 being able to swap out a Wizard template for a Were-form template, as in this example), but I believe that this is how it's intended to work, right Sanctaphrax?