Per Carroll's results in An Analysis of Power Consumption in a Smartphone: The backlight is either the lowest power local component (10%, 40mW) or highest (50%,

Per Carroll's results in An Analysis of Power Consumption in a Smartphone: The backlight is either the lowest power local component (10%, 40mW) or highest (50%, 400mW) depending on how bright it is turned up. The GSM radio is the highest power component (about 400mw), when it is working continuously (phone call). Related: a big contribution of smartphone OS optimizations and stuff like wifi 6 is about being smarter about turning off the radio for micro time slices when not needed. Laptops are similar, but it depends a lot on whether you are using a 15W CPU Ultrabook with no GPU, or 65W mobile workstation CPU plus a GPU.