Location matters because solar exposure is best in the Southwest, where fewer people live, but not very good in the Northeast, where the population density is high. A good way to see the problem is to compare the map for solar exposure in Figure 4.1 to the map of lights in the United States at night (Figure 4.3), which is representative of population density. For solar to play a large role in meeting the nation’s electricity demand, large transmission lines would need to be built to transport it from the Southwest to more populated areas. Large losses occur in transmitting electricity over thousands of miles because of heat in the wires, so it is inefficient to transport electricity over long distances. The losses depend on wire diameter, voltage, and even the weather because of ionization of air along the

wire. For 765 kV high tension braided power lines, the losses can be 6-7% per 1,000 kilometers (600 miles) (24). Transporting electricity over a couple of thou­sand miles would cause losses of 20% or so, which would dramatically reduce the already inefficient solar power available to the end user. These losses can be mini­mized by using high voltage DC transmission lines, but they are more expensive and there are currently very few available in the United States.

There is considerable opposition from affected landowners to the huge tow­ers and multiple lines necessary to transport high voltage electricity over long, or even relatively short, distances. A big controversy has arisen in Colorado over Xcel Energy’s plan to build a 146-mile, 235 kV transmission line with 150-foot tall tow­ers from the best solar resources in Colorado—the San Luis Valley—to the popu­lated Front Range. The transmission line is opposed by the owner of a 171,000-acre ranch through which it would cross, based on environmental and viewshed con­cerns (25). Similar concerns arise wherever large transmission lines are proposed.