CARMEL, Ind. — MISO is defending its methods for validating utility load forecasts after Dynegy last month charged that Ameren Illinois miscalculated its summer peak load forecast.

Michael Robinson, MISO principal adviser of market design, said the RTO’s Tariff obligates it to draw a random sample of load-serving entity demand forecasts to “assess credibility” of the forecasts. For the LSEs selected for the sample, MISO performs an ex post review of their previous year’s forecast and works with them to reconcile differences between their forecasts and those produced by Purdue University’s State Utility Forecasting Group.

“Ameren was a draw in the random sample last year,” Robinson confirmed at a Nov. 8 Resource Adequacy Subcommittee meeting. “We did have to come back and ask them for additional documentation. Some of their documents were a bit sketchy, I guess, but they gave us everything we needed.”

Last month, Dynegy called on MISO to develop a new process for verifying load forecasts produced by LSEs, claiming Ameren’s forecasts led to under-procurement in the capacity auction for Zone 4. (See Dynegy: MISO LSE Load Forecasts Require Tune-up.)

MISO said it found no evidence of systemic bias in forecasts. Robinson said Zone 4 was slightly hotter than normal at coincident peak this summer and all local resource zones were within two standard errors of their forecast values.

“The way we design this is the LSEs are the experts in the sense that they know when customers are building. They certainly have more information than we do,” Robinson said. “We don’t forecast ourselves on the zonal level for the coincident peak. We don’t have that kind of information.”

— Amanda Durish Cook