Visible light itself is not heat. I think the heat is more of a bi product. Light from halogen got more heat than light from a led, so its hard to tell how many lumens you need. Example.The old cars got halogen, and the glass on the headlamps never froze. If it was covered in snow, it melted. Then hid came and problems with ice film on the headlamp arrived (atleast in the arctic part of the world). Now the led made the problem even worse...