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EDD129 is the preferred index used to generate values used by AEMO to settle the wholesale market. Market Participants may use this EDD to reconcile estimated basic meter reads. EDD129 indicates three-hourly observations between 12am to 9pm of the current day. EDD129 is also known as EDD publish in the MIBB report. Further information is available in the Retail Market Procedure (Victoria) document.
The EDD129 formula is shown in the table below.
EDD129 = Temperature Degree Day (DD) Wind chill
0.038 * DD * 0.604 * Wind
0.18 * Sunshine hours
2 * Cosine (2*PI*(day – 200)/365)
Temperature T: This is the average of the eight three-hourly Melbourne temperature readings (in degree Celsius) from 12am to 9am of the current calendar day as measured at the Bureau of Meteorology’s Melbourne Station. Equal weights are applied to all temperature observations.
The Degree Day (DD) = 18 – T if T < 18
= 0 if T is greater than or equal to 18
T = (T12AM + T3AM + T6AM + T9AM + T12PM + T3PM + T6PM + T9PM) / 8
18 degrees C represents the threshold temperature for residential gas heating – this threshold (of about 65 degrees F) is a fairly common standard internationally.
Average Wind: This is the average of the eight three-hourly wind observations (measured in knots) from 12am to 9am of the current calendar day measured at the Laverton and Moorabbin Stations. Equal weights are applied to all temperature observations.
A localisation factor is applied to account for the shift from the Melbourne wind station (closed in 1999) to the average of Laverton and Moorabbin wind stations in order to align them with the Melbourne wind station reading. This factor is highlighted in red.
Wind = (W12AM + W3AM + W6AM + W9AM + W12PM + W3PM + W6PM + W9PM) / 8
Sunshine Hours: This is the number of hours of sunshine above a standard intensity as measured at the Weather Bureau’s Tullamarine Station.
Seasonal Factor (COSINE function): This factor models seasonality in consumer response to different weather. It indicates that residential consumers more readily turn on, adjust heaters higher or leave heaters on longer in winter than in the shoulder seasons for the same weather or change in weather conditions. For example, central heaters are often programmed once cold weather sets in resulting in more regular use. This change in consumers’ behaviour is captured in the Cosine term in the EDD formula, which implies that for the same weather conditions heating demand is higher in winter than in the shoulder seasons or in summer.