Rosewill 400W Power Inverter with 1x 2.1A USB Port $15.99 with free shipping (orig. $50)

Watts = PF * V * A
400W = 0.85 * 120 * A
A = 3.9A out

400W = 0.85 * 12 * A
A = 39.2A in

Plugging this into a cigarette lighter with a protective device (fuse) less than 40A (all vehicles) will likely melt the fuse under full load making the "400W" part useless.

If you decide to wire yourself, cable required to run this according to NEC is 10AWG, probably 8AWG with correction factors. However, your main issue will be voltage drop so make sure the inverter is as close to the battery as possible (console, under seat, etc). Not the rear of the vehicle.

It is a life saver for me, on long island. It runs my oil furnace for the last 5 days. My furnace draws approximately 200w(measured by Kill-A-Watt). Keep in mind that alternator(at least mine) produces only 75A*12V=900W. Some power goes to the engine itself, so 400w is maximum recommended for small cars.

This one is a bit better at only $1 more, as the one you posted did not have the 2.1A USB port.

Same here during hurricane. No power for 4 days.

Your actually running from the battery, so you can draw as much as the battery can handle.

My 1000w ran my fridge off of the car along with other things. The fridge would not start unless the car was running which was about 14v.
I would start the car when the battery reached around 12v. Any lower will shorten battery life.

Anyway, I bought the same 400w unit without the USB from the last deal. Its well built and seems to work good.

Wow, guys this thread is DEEP, making me flashback to my EE classes at UT@A, and my days as a Nuke Electrician in the USN . Thanks Op, got one!

Regarding the fridge post, (and any other devices that require high starting currents), there is a HUGE difference between the start-up requirements and running requirements. On a sub, we had a particular order to start/restart systems as we changed power sources (reactor to battery, start-up to go underway, etc.), because of that huge difference. BUT, in many of the devices on a sub (and in devices meant to be portable I hope, don't have any, so I do not know), large capacitors can by used inline to provide the start-up current required without causing voltage droop. SO, let pretend that you want to use a mini fridge from home from your 12VDC car system through this inverter. You could purchase multi farad caps and with some simple wiring, put your "surge power source" between the inverter and your device.

As also recently having my home without electricity for about a week, I spent roughly 48 hrs straight rewiring the majority of my home to run from a generator. Basically I wired the generator into a transfer switch, and the transfer switch to a fused mini power panel, and then ran certain breakers for "necessity loads" like fridges, freezers, lights, etc. from my main breaker panel to my emergency breaker panel. It was 5000 W I believe, about 1/4 of what I needed for whole home power... but it was the biggest one I could find locally (most were sold out obviously), and my lesson learned there is that refrigerators SUCK . Steady sate (when their internal temp is below threshold to kick on compressor), they take almost no power. As soon as someone opens the dang door, of course the threshold is hit and the compressor will kick on, drawing that huge starting current AGAIN, and AGAIN, etc. So for devices like that, if you want them running off of a system like this, either buy one built for it (which will most likely have the charging cap, etc. built into it or a much lower power requirement), or make the DIY starting power source a permanent attachment to the device. Also, get a Killowatt, multimeter, etc. and run whatever device through its starting, steady state and power off cycles and watch the peak amperage. If you are actually planning on several devices(say a couple of week camping trip with all of the conveniences of home), then you should have multiple circuits with their own protection, use a mini breaker board, DON'T rely on your cars fuses (unless you bring an assload of extras to replace them as they pop ).