Today I depleted the EV miles in my Prius Plug-in Hybrid before starting up a mountain, going from about 1500 feet to 6300 feet. It was HV all the way up. Upon reaching the top, I parked for about 8 hours. When leaving, I started the PIP and only the green ECO light was lit. The ICE came on after a few seconds. I touched no buttons, but started down the hill in B. After a short time I noticed that I had 1.5 EV miles available, and the green EV light was lit alongside the green ECO light. I don't know if EV miles showed before 1.5 miles or not. As I went down the mountain, I touched no buttons, and the EV miles increased to 16.4 when I heard the ICE go very fast to burn off extra electricity, just like I used to hear most of the way down in my 2004 Prius. The EV miles increased to 16.7 at the highest when I came to the bottom of the hill. I mention this because I thought I had read other posts saying once the EV miles are depleted and the PIP automatically goes to HV, you can't get EV miles back. I had taken the to mean "unless you plugged in." My experience is that PIP regeneration can bring back EV miles as well as plugging in.