A battery of suitable size, keep in mind every 1aH is basically 1 hr of use. A charger and suitable terminal connectors for the battery you choose. You also need the 6105.500. Don't get carried away with the battery. Realistically after a hurricane you won't have power to cool the tank, getting ice for yourself can even be an issue so in a long power failure in summer you are pretty much screwed, try for a back up that will last a day, in summer after a few days the inhabitants will basically be cooked anyway so flow is a moot point, with a solar charger you will be able to keep running much longer if you can set it up on the roof or in the yard. The ideal for your situation in my opinion would be a 25-30aH gel cell battery and a small solar charger.