I have one, and i drop right around 1100 dollars to fill it. last about 6 months maybe longer depending on your heating demands. mine supports 2 heaters, and 2 water heaters. no cooking, nuthing else.
i hate it.
hate it- hate it- hate it.
have no choice though, i live too far out in the sticks for natural and my house is too big to try and rely on electricity..... so during the winter i burn wood to heat... spend all summer doing "free" tree topping....