Lady Laura 
Viss
Tiota Sram@Viss @cmconseils depending on whether lighting is pre-baked, they may only use real electricity because displaying lighter-colored pixels uses more electricity in your monitor than displaying darker-colored pixels. In those cases, one could in theory invert their monitor colors to cause the in-game lamps to use net-negative real-world electricity.
@tiotasram @cmconseils the gpu, cpu, pci bus, wifi etc all still require power to make the lamp show up in the game, and even if its not visible, the rendering engine knows its there, so even when it's off screen its still technically being allocated watts
I think I was thinking about it in the sense that the lamp being on takes more energy than the lamp being off, over time. But you're right that the extra polygons of the lamp model use energy that could be saved were it not included, even when baked lighting means that the CPU/GPU don't work any harder because of the "illumination" the lamp provides.
For a dynamic light like a flashlight or headlight the player can toggle, there's extra cycles needed during rendering for sure.