Density In the science world the ratio of the Mass of a substance to its volume. Because many substances, especially Gases (see States Of Matter), can be compressed into a smaller volume by increasing the Pressure on them, the Temperature and pressure at which the density is measured are usually specified. See Specific Gravity In the Power world density is a measure of the number of customers per line mile. Municipal systems such as City Utilities in Springfield have a very dense system of 50 customers or more to the mile. Rural electric cooperatives have a very low level of density, often below 5 customers per mile. Webster Electric has slightly over 7 customers per mile, highest of any Sho-Me member cooperatives. All other things being equal, the higher the density the lower your rates (see Rates - Residential) should be. Why? It costs approximately $50,000 per mile to build a new three-phase, 477 MCM ACSR Distribution line to serve 5 customers per mile or 50 customers per mile. So the higher your density, the lower the amount of fixed costs per consumer, and your rates can be lower to recoup the initial investment. Of course the economies may change when you get in a large city where both distribution and transmission has to be buried in vaults.