Mom and Dad's PV system from Solar City (www.solarcity.com) is a leased system that is grid-tied and will roll their meter backwards when it generates more than they use.
||Mom & Dad's 2009 PV generation
Mom and Dad installed a photovoltaic system in April 2009. This is the graph of generation through the end of the year. Total generation was 2,830 kWh. According to the website, that is $526 in electricity, or 1.8 mature trees of carbon offset.