I’ve seen 10-12W easily on 4K for soc without av1. your soc (intel 11 gen) should support av1. try to play the video on mpv (with yt-dlp integration) with various hw acceleration options to see if it changes. probably your browser is software decoding.

for hardware decoding supported soc too I noticed 2-3W of extra power usage when playing youtube from website compared to mpv or freetube. the website seems doing inefficient js stuffs but I haven’t profiled it.