I got one of the jump starters with built in 12 volt power out let, usb, already had a little inverter, don't remember watts, some even have a air compressor built in, and light, good for jump starting lawnmower, inflating tires, powering weather radio when power out. Pretty handy to have around. And a lot easier to carry than a car battery.
http://www.walmart.com/ip/Cobra-Elec...tput/146495563
Already has 110 outlet, the one I got doesn't have a compressor or 110 built in and might get another one just for backup power around the house.