Lamp on invisble layer calculates


As you might have guess I have a problem. I’m doing a game in BGE with rather large levels. Right now I’m on my way of optimzing it which has went pretty good until… the lightning. I thought it would be a good idea to create emptys which spawn lights when the player is nearby, and then the light turns off when it’s far away. This benefits some, but now as much as it should do.

Here’s the problem:
It seems like the lamps on the invisible layer calculates and makes the game slow down. When I deleted 10 lights from a layer that was invisible when the game was running, the framerate went from about 15-20 to 40fps. How do I avoid this? Why is this?

Thankful for reply,