We received the following email regarding the cleared energy and offer stacks report on EMI: 

I was looking at the offer stacks on EMI this morning and have a query on how wind generation is being treated.

It looks very much as though the MW Max value from the wind offer is being used. With the implementation of the wind offer arrangements work this tends to be static number equal to the installed capacity (it may have been used that way prior too?). 

As a concise example of the potential distortion this can have on 6 Dec HWB0331 MAH was on an outage, as was the WPI injection at the same GXP. In the EMI offer stack for that day there is 37MW of Offered gen at $0-10 for every period of the day. In aggregate it can be notable – I calculated a difference (using FP data not offered FOGP – see below) of ~230MW for the NI in pd1 of 6 Dec 2019.

If the EMI offer data comes from WITS, rather than the final pricing case, I’d suggest using the FOGP (forecast of generation potential) as a better figure. If the data is able to source the final pricing case then it would be possible to get the ‘actual’ offer. The ‘actual’ offer is derived from the FOGP or actual metered generation depending in accordance with the wind offer arrangement changes. Due to the use of metering data this value isn’t available until after the fact so it cannot be reflected in submitted offers.

We are aware that we haven't yet updated the offer stack report to account for the new wind offer arrangements. We noted back in September that we'd get to it soon. Unfortunately we are currently struggling with some human resource constraints so at the moment everything is progressing much more slowly than we'd prefer. At this stage, given other priorities and resourcing, I would estimate that we'd be doing well if we got this report modified during Q1 2020.

FWIW, our EMI offer stack report is driven by the data found in the final pricing SPD case. The offers dataset that we publish is based on data received from WITS and shows the evolution of all offers through time for a given trading day - bona fide offer revisions notwithstanding, the last offer submitted wil be the offer used in final pricing.