PacifiCorp 2007 Integrated Resource Plan (May 30, 2007)

PacifiCorp – 2007 IRPChapter 4 – Resource Needs Assessmentcates that existing resources do not meet obligation. If existing resources equals the obligation,then the reserve margin is zero percent. It should be pointed out that the reserve margin can benegative when the corresponding position is non-negative. This is because the reserve margin ismeasured relative to the obligation, while the position is measured relative to the obligation plusreserves.Capacity Balance DeterminationMethodologyThe capacity balance is developed by first determining the system coincident peak load hour foreach of the first ten years of the planning horizon. Then the annual firm-capacity availability ofthe existing resources is determined for each of these annual system peak hours and summed asfollows:Existing Resources = Thermal + Hydro + DSM + Renewable + Purchase + QF + InterruptibleThe peak load and firm sales are then added together for each of the annual system peak hours tocompute the annual peak-hour obligation:Obligation = Load + SalesThe amount of reserves to be added to the obligation must then be calculated. This is done byfirst removing the firm purchase and load curtailment components of the existing resources fromthe obligation. This resulting net obligation is then multiplied by the planning reserve margin.The non-owned reserves are then added to this result to yield the megawatts of required reserves.The formula for this calculation is the following:Reserves = (Obligation – Purchase – DSM – Interruptible) x PRM + Non-owned reservesFinally, the annual capacity position is then computed by adding the computed reserves to theobligation and then subtracting the existing resources as in the following formula:Capacity Position = Existing Resources – Obligation – ReservesLoad and Resource Balance AssumptionsThe assumptions underlying the current load and resource balance are generally the same asthose from the 2004 IRP Update with a few exceptions. The following is a summary of theseassumption changes.● Front Office Transactions – For the 2007 IRP, front office transactions were taken out ofthe existing load and resource balance in order to treat them as potential resources that theCapacity Expansion Module can pick from. This was done in order to treat the front officetransactions on a comparable basis to other supply-side resources.● Wind Commitment – In the 2004 IRP Update, 1,400 megawatts of wind were included asplanned resources in the initial load and resource balance. For the 2007 IRP, 400 megawattsof the overall 1,400-megawatt commitment are included in the initial load and resource bal-79