A method for use in calculating a possible power output of a wind turbine. A series of performance data samples is acquired. Each performance data sample includes a meteorological condition and a power output indicated at a first time by one or more sensors associated with a wind turbine. A transfer function is calculated based at least in part on the series of performance data samples. The transfer function relates power output to the meteorological condition. A possible power output is calculated based on the transfer function and at least one meteorological condition indicated by the one or more sensors at a second time.