against them. Every customer on a central-station circuit will ultimately purchase and use lamps of this character. The situation contains a menace and a promise, a menace which cannot be ignored, a promise which must be fulfilled. The menace is in the fact that the reduction in the cost of providing light to the average customer can never be so great as the customer expects. He inevitably associates that two-thirds reduction in current consumed with a two-thirds reduction in cost. The decrease in cost of furnishing light with the high-efficiency lamp is almost entirely measured by the ability of the central station to take on additional consumers who can assist in bearing the fixed expenses. The promise lies in the opportunity. Never in the history of our industry has there been the opportunity which now presents itself to the central station for increasing the number of its customers, decreasing the cost to each of them, and increasing profit to itself, through the use of the high-efficiency lamps. Demand and Diversity Factors and Their Influence on Rates by J. R. CRAVATH (Reprinted from The Electrical World Demand and Diversity Factors By J. R. CRAVATH 1910 Introduction-Definitions Demand factor is defined as the highest percentage of connected load which is ordinarily in circuit. Thus, if a central-station consumer has 10 kw in lamps connected and his highest maximum demand is 5 kw, he would be rated as having a demand factor of 50 per cent. Diversity factor is commonly defined as the ratio of the sum of the maximum demands of a given group of consumers at different times to the actual maximum demand made by the group at one time. This likewise frequently can best be expressed in per cent. For example, a group of 10 consumers connected on a certain secondary main might cause a maximum demand of 3 kw on the transformer supplying that main; but if a maximum-demand meter were installed on each consumer's service the sum of the maximum demands recorded by these meters for any month might be 9 kw in certain classes of work. Expressed in per cent, the diversity factor of this load in relation to the transformer would be 33.33. This difference between the sum of the individual maximum demands of each consumer and the actual maximum demand on the transformer is, of course, caused by the fact that the maximum demands of the various consumers do not occur at the same time. In other words, there is diversity in time of maximum demand. Importance of Demand Factor and Diversity Factor The existence of diversity and demand factors in centralstation business has been recognized since the earliest days, although it is only recently that these brief terms have come into use to express these relations. It may also be said that although the centralstation industry has been dependent for its very existence on diversity and demand factors, the study of these factors has not been as thorough as it should have been. It is only recently that much activity has been shown in the study of these factors, which have an |