Major electrical problem?

I have an 07 Prius with 191,000 miles on it. It's been great so far, I haven't had to replace anything major or that isn't to be expected with higher milage.

One day about a month ago, I went to start my car and none of the dashboard lights/odometer/gas gauge would come on (and yes, I checked the dimmer switch) and I didn't get any of the usual seatbelt warning beeps upon startup. I also noticed that on the center screen, the backup cam and the mpq calculator were not working. But despite this, the car was still driving and I took it to work like that. Afterwards, I went to the Toyota dealer and was basically told that this isn't common, they've never seen it before and they would have to run a full diagnostic. I scheduled an appointment for them to do that the next day, but as I start the car to leave the dealer... everything came back on and worked perfectly.

it was fine for a couple weeks, and then it started doing it again on and off. Now, it's happening every day, but not permanently. I might start the car for the first time of the day, and those things arent working. I stop at the gas station 5 minutes later, and when I leave there, everything's perfect. It's unpredictable and doesn't seem to follow any patterns.

However it seems to be spreading and causing new things to stop working that were fine in the beginning of the issue. Now, my power button won't turn the car off when it's doing this. I have to insert the key, hold the power button down to force stop it, which shuts off everything but the radio and center screen, and then when I pull the key out the car is off.

Has anyone else had this issue or have any ideas on what it might be? I will also mention that I'm about to replace my idler pulley, and someone had told me that the tensioner/belts might be able to cause an electrical issue. I have also had my check engine light pop on in the past for my 02 Sensor, but it went off and stayed off, so I never fixed it. Could it possibly be something that simple, or does it sound like a major electrical issue that's gonna cost me thousands of dollars?

And please use layman's terms... I'm not that smart when it comes to cars.

 

Thank you guys so much for your responses. After reading about all the symptoms of a bad Combination Meter and watching the videos, everything matches up EXACTLY so I feel sure that's what it is. And at around $450 to fix it, that's much much less than the nightmare repair bill that I was expecting would wipe out my entire vacation savings. I feel 100x better.

But just for good measure, I went out and did the battery test. I got 9.6V in ACC mode, and 13.8 with the car on and engine running... I'm guessing that the 9.6 number is bad? So maybe I actually have both issues? At least it's the cheaper battery and not the scary-expensive hybrid battery.