Just watched this talk and posted it to HN (sorry for the dupe!), Bert made a lot of great points in under 45 minutes!

There was some technical trouble in the first minutes, so skip to 4:46 (https://youtu.be/XntLynSlYjI?t=286) to get to the talk.

tl;dr: Measure the energy use of your systems! Both on the server and the client side. You could save energy and money, and also have a really good excuse to have fun optimizing your code :)