The California Single Family Water Use Efficiency Study provides a snapshot of the state of single family water use in over 780 households drawn randomly from 9 water agencies in North and South California. High resolution flow trace data were obtained from the customers’ water meters, which were disaggregated into end uses using Aquacraft’s Trace Wizard program. The data were collected between November of 2006 and August of 2008. Results are provided as descriptve statistics, and regression models. Both domestic and landscape uses are discussed and comparisons are provided to kwown efficiency benchmarks.