BESS Wholesale Arbitrage Revenue Calculation Error

[scottbosman]

Upon reviewing some of the BESS facilities in the NEM, we noticed some potential calculation errors for wholesale market turnover. We've noticed that to calculate total market value you have added both Discharging and Charging market values. For example with Hornsdale BESS in Jan 2024 the Discharge value is 260k and Charge value is -102k, resulting in net revenue of 158k. We've compared both other NEM data websites (NEMBESS) and our own modelling software and we've calculated different values. NEMBESS states that net energy revenue is ~367k and our model is indicating ~354k (note we're still refining accuracy).

This leads me to believe that you should be subtracting charge value from discharge value (i.e. 260k - -102k = 362k) which is roughly in the ballpark of both of our estimates. I completed this analysis for 6 other BESS sites (Wandoan, Bouldercombe, Riverina 1, Wallgrove, Ballarat, and Hazelwood) and the estimated revenue using this method is significantly closer to both our modelling and NEMBESS' figures.

Note that this may not be the solution, and there may be underlying issues with the Openelectricity modelling and this just be a coincidence, but 7 sites in total with a maximum of 4% difference in CY24 yearly revenue compared against our modelling and NEMBESS suggests that it may be a simple fix!

Hope this helps and if you need more clarification to what I am referencing feel free to contact me at scott@gridcog.com.

[nc9]

Thanks for this Scott - will be taking a look at it in a moment