47 



Gas Combined-Cycle Costs vs. PF Rate Graph Assumptions 



Gas Combined-Cycle: 



• Based on Bonneville supply curves and gas forecasts. Costs generally correlate with 

 Bonneville's acquisition programs experience of the past few years. 



• 90% availability (industry experience of 90-97% with this and similar technology). 



• Real escalation rates for spot gas prices: High = 5.9%,. Medium = 3.4%, Low = 0.0%. 



• Displacement alternatives assume plant runs on gas half the time and is displaced, i.e., 

 "runs on water" half the time. Opportunity cost of nonfirm is 15-mills/kWh (1993$). 



• Levelized cost (1993$): High Gas - Baseload: 54-mills 



Medium Gas - Baseload: 39-mills 



Medium Gas - 50% Displaced: 35-mills 



Low Gas - Baseload: 28-mills 



PF Rate Shown in Graph: 



• Based on medium forecast from BPA Wholesale Power and Transmission Rate 

 Projections 1992 - 2013 . Nov 1992. 



• The effective PF rate depicted in this graph (92% of Bonneville's published average PF 

 forecast) is the rate a utility would avoid by building a new gas CC. It is derived using 

 demand and energy charges applied to a load which is equivalent to the expected 

 availability of a gas CC (90%). The average load factor implicit in the published 

 average PF forecast is much lower than this. 



• Levelized cost (1993$): Published PF = 27-miUs, Effective PF (graphed) = 25-mills. 



Other Assumptions: 



• It would be incorrect to infer equivalent reliabihty between a gas CC and the PF rate. 

 The cost of backup supplies for the gas CC is not included here. Unless a utility has 

 cheap and reliable backup supplies, the system cost for a gas CC of equivalent 

 reliability to the PF rale would be somewhat higher. 



• Wheeling costs of a gas CC are not included and could be - 3 mills/kWh. 



• General inflation rate is 4%. 



Bonneville Power Administration 

 July 12, 1993 



