As color temp rises, Lumens per Watt falls. Granted, you get to see some beautiful shades of lavender, blue, turquoise etc. but if you want the most efficient system, 4300K, even a 3900K will provide it. I probably gave up 100 to 200 Lumens going with 5000 but I went with 55 Watt to make up the difference. I've driven next to quite a few 8000K and 10000K installations and the road in front of them is quite dark and completely void of natural color. They sell them for the "cool" factor.