When I started my meditations, I didn't 'notice' much change in energy. Probably because I am not new to meditations. However, within a few weeks I did notice that there was a small change in energy levels. I am currently in the intermediate stage of my meditations in less than six months. I was doing one of the exercises with regards to breathing energy through the chakras and noticed a change in energy levels within a week.
From what I understand, my lower chakras (upto the heart chakra) are completely open and are strong. I am still working on opening my other chakras as well as my third eye currently.
This is my personal experience.