Yes, replace headlight bulbs in pairs. The OEM bulbs are 55w H11 bulbs. Posted via the PriusChat mobile app.
Here's the parts list for the 15 PiP headlights. There's some surprises in that list, including 2 separate replacement Headlight bulbs. Which looks like from your pics you might need one of them on one side and the other one on the other side. Just guessing so far though. Headlamp - 2015 Toyota Prius Plug-In Might even be worth the $20 for the techstream 2 day subscription for your model so you'll know exactly which parts you need and more importantly how to change the bulbs. techinfo.toyota.com
I frequently steer people toward TIS, but where bulb replacements are concerned, it's pretty much always possible to find what you need to know for zero cost from the "bulbs" section of the owners' manual and from searching on parts.toyota.com. The repair manual on TIS will be useful if you need more step-by-step on how to change the bulbs.
it's pretty simple, just a quarter twist to get the holder out, and pop the old bulb out and new one in. i forget if i did low or high, low i think. the passenger side is difficult. tight space to work in, and i have large hands. most difficult part was lining it up properly to insert and twist back in. i managed it, with a few scrapes on my arms and hands. i'm sure you can disassemble things if necessary. watch
FYI, don't get any grease or even oils from your fingers on the glass part of the bulbs, it will create a hotspot on the glass and can lead to cracking/failure. Posted via the PriusChat mobile app.
For the passenger side headlight I found it easier to put the replacement bulb in and then hook up the connector. Spent lots of time trying to get it to seat properly connected to the wiring harness, but had no problems once I unhooked it and just put the bulb in first then connected it.