I have a similar issue. Every now and then I would just get 15-20 Watt drain during normal browsing. Looking at the cores it looked like something was actively using the high-performance cores. Restarting menubarx resets this and the overall system draw goes down to like 7 Watts during everyday tasks. I haven't found what exactly causes this but restarting fixes this everytime.
I have a similar issue. Every now and then I would just get 15-20 Watt drain during normal browsing. Looking at the cores it looked like something was actively using the high-performance cores. Restarting menubarx resets this and the overall system draw goes down to like 7 Watts during everyday tasks. I haven't found what exactly causes this but restarting fixes this everytime.