I had a few modifications performed on my Prius Prime. One was the installation of this 12v accessory outlet/cigarette lighter socket in the hatch area. It is installed in what the owner's manual refers to as the right side auxiliary box in the luggage compartment/cargo area (under the luggage compartment light). I wanted to be able to run a CPAP machine without any concerns, so my installer wired it directly to the 12v battery with a 10 awg wire (with a 20 amp inline fuse). I asked him to install the rocker switch so that the outlet could be either always on, or on only when the car is on. If that rocker switch is in the "on" position, the outlet is always active. In the attached photos, you can see how a cable emerges from that compartment (yellow arrows) and goes into my car safe/lock box (the lock box has an indentation in the edge to allow a cable to pass through, which I've highlighted with a green arrow). I can leave a device charging in there, and have it only charge while the car is on or even when I'm parked.