Power Inverter Hardwire

Question...Where/what is the 12volts under the dash?  I'm trying to do the same thing on my jeep.  I actually need to install an inverter and a 12vDC fan...

anything that is getting power (cig lighter etc.) is 12 volts.  Some are accessories and only run when the car is on, others are constant.  Depending on what kind of draw you need, you can plug in to one of the under dash sources.  If you need to draw a fair amount or power or just want some saftey and head room, run a wire direct to the battery and ground the Neg / black. This will allow you to draw as much power as the inveter allows.  If you plug into the cig lighter and you won't be able to draw much power due to the size of the wire.