Ehouse
Minister of Fire
I wouldn't advise using a car battery. Car battery plates are thin, designed to produce large amperage for short bursts. For powering things over time, you need a deep cycle battery (thick plates), with less ability to produce lots of power in a burst, but much less likely to sulfate, which is what kills batteries.
To wire into house, you need an inverter (converts DC to AC current) and a way to recharge the batteries. Unless you are very familiar with electricity, do not attempt on your own. I am unaware of packages and you will need a good knowledge of current calculations, wire sizing, etc. I designed mine with my electrician, but even then it required research.
Google New England Solar. They have a good pamphlet on Gen/inverter/battery setups, and they sell packages as well.