Percentage

Calendar Year	2000	2001	2002	2003	2004
Generation Energy Efficiency	99.6	99.38	99.77	99.81	99.72
Distribution Energy Efficiency	96.4	96.5	94.9	no data	96.2

Generation Energy Efficiency is defined as the ratio of net generation to gross generation. Gross generation is the amount of electricity produced by a generating unit. Some of that electricity is then used for station service – to operate station equipment and supporting infrastructure – leaving the net generation as the amount of electricity that actually leaves the generating station site and enters the transmission system. Energy efficiency varies by type of generating facility with hydroelectric stations generally using less electricity for station service than fossil fuelled stations. In F2005, Generation energy efficiency is less than the previous year due to increased market purchases made necessary by lower than normal water inflows to reservoirs. This measure does not necessarily reflect the efficiency of the entire system – hydroelectric, thermal and IPPs – as one part of the system may be operated less efficiently to obtain greater performance from the overall system. Efficiency measures that reflect the entire system are being developed and will be used in future reports as available.

Distribution energy efficiency is the ratio of the gross electricity input to the distribution system from the transmission system to the net distribution electricity output that is actually delivered to customers. Distribution energy efficiency is affected by line length, line voltage and the age and efficiency of distribution equipment such as transformers and switches. Distribution efficiency remains at historical levels.

Because changes in system-wide internal energy efficiency are generally small over time, this measure is reported every three years consistent with CEA reporting practices.