Energy usage is directly related to memory usage: more memory used means more energy required to access it.
We need to get back to writing efficient code again. By that, code that minimized memory and CPU usage, and is not a bloated multi-process pig like Chrome.
This multi-process crap is the biggest pile of crap, it increases complexity by SEVERAL ORDERS OF MAGNITUDE, it takes something that used to be a clean elegant design like WebKit and makes it into the multi-process monster that is completely and totally unintelligible to anyone other that a few core devs. It wasted a massive amount of memory, wastes CPU and wastes energy.