Fig. 4.

Cost differences between wind build-out scenarios. Cost differences are expressed as percentage of total annual wind capacity cost, which is constant across scenarios. Actual cost differences in millions of USD/y are labeled above each bar for the base-load sensitivity case. Positive percentage and cost values indicate cost savings of scenario 1 compared with scenario 2, and negative values indicate additional costs of scenario 1 compared with scenario 2 in each panel. Costs were estimated assuming three different possible conventional capacity technologies—natural gas combustion turbine (CT), hydropower, and scrubbed coal (x axis). (A) The cost savings of the Min-Net-Demand over the Min-LCOE site selection approach. Positive values indicate that Min-Net-Demand is more cost effective. (B) The cost savings of the Interconnected over the Isolated scenario. Positive values indicate that the Interconnected scenario is more cost effective. (C) The cost savings of the Top-50% over the All-Zones site selection approach. Positive values indicate that the Top-50% scenario is more cost effective. The set of points for each bar (defined at bottom) shows results from load sensitivity analyses of four plausible future load growth scenarios: “Climate - extreme warming,” “Climate - warming,” “Daily peak increase,” and “South Africa - hybrid.” See SI Appendix, section S1.3.4 and Figs. S10 and S11 for descriptions of the load growth scenarios.