Is there a way to reduce the CPU usage of a Gmail tab in Chrome browser?

Double-check your hardware acceleration settings in Chrome. Google's scripting (JS, CSS animations) is very "modern" which means it performs poorly on CPU but runs very, very fast on GPUs via modern browsers ... assuming acceleration isn't turned off, which would cause very high CPU usage.

Or there might be a bug with HW acceleration making it nuke the CPU. Firefox and Chrome like to trade off on whose acceleration is borderline worthless and breaks websites. Toggle it, and if turning it off fixes the issue try turning it on again after a Chrome update or three.

I found this thread and thought my experience could be useful to somebody. I had the very same problem: when logged on Gmail with 2 tabs, 2 accounts, the Gmail tabs took almost 500 MB of RAM and continuously spiked on CPU usage, every few seconds they went from 1-2% to 50%. I disabled all extensions, disabled hardware acceleration, tried everything suggested but with no result. At last I realized I could try to disable the chat and calendar gadgets I still had open in my Gmail tabs. Puff! Magically everything worked fine! Now my 2 Gmail tabs take around 180MB and the CPU usage is constantly around 0 !!! Try to believe. Chrome v. 50.0.2661.102 m, on Win 7.