4. Rounding Convention

The current rounding convention for local RA obligations provides that RA obligations are met by rounding to the closest megawatt. This convention was adopted in D.06-06-064 and expanded to system RA obligations in
D.07-06-029. The current rounding convention can lead to small discrepancies between the Energy Division's review of whether obligations have been met, and the ISO's allocation of local RA obligations to LSEs. These small discrepancies can at times cause the ISO to find an LSE as non-compliant while the Energy Division does not.

At the January 27, 2012 workshop, Energy Division proposed rounding to the 0.5 MW instead of the 1.0 MW level, which should reduce (though not entirely eliminate) discrepancies. The ISO proposed that the rounding convention should be modified to be consistent with the ISO's 0.1 MW rounding requirements. In the transcript for the workshop, Energy Division staff summarized the discussion of what rounding convention should be used for counting RA resources: "(the k)ey questions that came up during the discussion focused on whether the preference was to round two decimal places versus rounding clear up to one MW...and (it is) important to keep (in mind)...that some LSEs had trouble purchasing at lower than one MW quantity."⁷

In comments, SCE agrees with the ISO that consistency in the rounding conventions across both organizations is preferable, and notes that accuracy favors a more granular approach. If that is too difficult, SCE advocates a
0.1 MW rounding approach. DRA proposes that the RA program should utilize MW figures for rounding consistent with the ISO for its jurisdictional LSEs, with an exemption allowed for very small LSEs.

We will adopt a new convention of rounding to 0.1 MWs. This approach is much closer to the ISO's convention, will lead to a minimum of discrepancies between Energy Division and ISO reviews, and will not require different Commission standards for different LSEs.

⁷ Reporter's Transcript 28.