1 - A really efficient lighting coming from objects. Using or not using them make no difference. Is really hard to tell if have a source of light using stuff created by crafting
2 - Houses and apartments with option of lighting configuration:
A - as an active option (not to use the limit of objects using lamps or other objects.
B - Environment (to use only the light source used for objects)
3 - Homes that depend on control towers would be without light if the control tower runs out of fuel