What's this metal box under the driver's seat?

[JPark]

I bought my Vibe used from a rental agency, and I'm still discovering little surprised here and there. Last week I found the key fob in one of the secret compartments. Yesterday I found an electrical box mounted underneath the driver's seat. It's silver, about the size of a cigar box, looks pretty heavy, and has cooling fins on it. It doesn't have any identifying writing on it. It looks a little like an amplifier except I can't imagine they'd put an amp in a rental car. Any thoughts?

[joatmon]

That is the AC inverter, converts 12V DC into 115 V AC. The switch and outlet are in the dash, under the heat/AC controls, behind (or in front of, depending on your point of view)the shifter, but the guts that actually makes the 115 V AC is that silver box under the driver's seat.If your Vibe had a factory amplifier, it would be under the front passenger seat.

[JPark]

Makes sense. I had wondered how they did that without an inverter. Answer is, they don't. Thanks for the help.