Each gray-shaded circle indicates a renewable energy zone (REZ) hub. Blue circles indicate hubs with significant geothermal potential: Oregon south, Idaho southwest, Idaho east, Idaho southwest, Nevada north, Utah west, and California south. A hub represents a conceptual step-up transformer where the electricity generated by all renewable resources in the REZ would get onto the transmission system. Hub circles are scaled to show relative annual production potential of all renewable resources in the REZ. Circles are not intended to indicate precise location of a new substation; actual collection point may be anywhere in the vicinity of the hub.