Are you familiar with the
Prius' warm up stages? There's a chance that you could be stuck in S3 and not make it to S4 (full hybrid operation) until late in your trip, if at all. You need to reach operating temp (73C, 163.4F), stop with the ICE running (or hold the brake and blip the gas to get it to turn on, if it was off when you stopped), and let it idle 5-10 seconds before it'll shut off and go into S4. It's kind of silly, because having a perfect commute with all green lights and no waits at stop signs will prevent you from getting max MPGs.
I like to have instrumentation that shows at least the ICE RPM and coolant temp. This allows me to get a good idea of what stage the car is in and what options I have available (the app Hybrid Assistant shows what stage you're in, if you want to be sure). Add an EV mode button to kill the ICE before hitting S4, and you can get pretty good mileage on short trips with lots of <40MPH driving.