12-12-2011, 03:31 PM
Battery banks make zero sense for a grid-connected house. Batteries are high maintenance plus they create a huge hit on efficiency. As billb noted, grid-connected PV dumps power into the grid, running the meter backwards during sunny afternoons, then takes it back again when needed. The grid is better than 100% efficient since sunny afternoons are usually peak periods when rates are high, whereas nighttime is not. At my house, my PV system generates power that I sell at 32 cents/kwh peak rate, which I buy back at 8 cents/kwh.