1.21 gigawatts? 1.21 gigawatts! Great Scott!...
Finding all the power you need
The next step in our project is converting our cars DC power (battery) into the AC power we need. For this, we need something called an
Inverter
Odds are youve seen or even have an inverter but didnt know it. They come in many configurations but here are some common ones.
Compact, aka "mini" inverter

Used when power needs are low or compact size is required.
Many companies make these with specific power "ends' on them for their respective device. They then call them "official" and charge you a small fortune.
Please Note: There are devices that look similar but are NOT inverters. They are more like outlet multipliers (they simply turn one cig lighter into 2 or 3 or whatever) *see here:
http://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=270-1525 * They will work in a system but that system requires you have car kits for EVERY item you wish to use. I much prefer having one inverter, and being able to plug in any two or three pronged home electrical device I wish.
Standard Inverter
The standard inverter is a workhorse. Its bigger but can usually handle more devices and more power hungry devices. It tends to be cheaper per watt than a mini as well.
So SDC, which one should I buy?
The choice,my friend,is up to you. If space is an issue and your power needs are low enough, feel free to buy the mini. I, however, much prefer the standard for a few reasons:
#1 More power which allows me more devices and a wider range of devices
#2 Cheaper for the same wattage
#3 Replaceable fuses mean if a surge happens I only need to replace a fuse, not the whole unit
#4 Dont it look so much more badass?
Ok SDC, Ive decided what type I want now how do I decide which wattage to buy.
Ok, take our earlier power calculation of all the stuff you want to hook up. Add to that 25w (I add 50w but Im paranoid by nature) That number is roughly what you ll need wattage wise.
Dont rush off to buy one yet. Lets be smart about this. While thats all we *need* maybe there are other applications we can use an inverter for or we can give ourselves a cushion for future uses/devices. There is,however, one important thing to consider when making our decision:
Car manufacturers limit the output of their cig lighters. You need to find out what the AMP rating is of your cig lighter to find out your limit (see owners manual) Here are the 3 most common:
10 AMP - no more than 120W
15 AMP - no more than 180W
20 AMP - no more than 240W
So as you can see, you can have a 400w inverter but youre not going to get more than 120w,180w,or 240w out of it (depending on your cig lighters AMP rating) unless you hardwire it into the battery.
For the majority of us, a 175w or 200w inverter should be more than enough and pretty much all we can handle AMP wise.