This morning on my 60-mile commute, I noticed the EV usage indicator said it used 0%, and my MPG was about 50.1 instead of the usual 59-62. Why didn't it use the battery at all? Usually it says anywhere from 6 to 20% (I don't really know for sure, but the 0% from this morning seemed really odd to me).
welcome to priuschat. sounds like something is wrong, but hopefully just an anomaly. let us know what it does next week, and keep an eye on the battery charge indicator whilst driving. all the best!
If you speed was 45+ mph the entire way, you wouldn't use EV mode. Did you have unusually light traffic?
My guess is the EV use is usually at the beginning of your commute, and cooler temperatures meant you had your heat on, which prevented the ICE from turning off. Eco mode can help prevent that somewhat, but not completely. The second guess is that your traction battery vent is blocked.