Intels Hybrid CPUs offer a potential for powersaving, when for less resource intensive tasks the E-Cores are used, instead of the P-Cores. Xen supports this via the "xl" tool, but that means setting the preferences allways when a VM is started. So i wrote a python script (here) to help with this. It uses the Qubes admin events to set the core preferences for each vm when it starts and also has a option to put some VMs in permanent performance/powersaving mode.