[en] Two main questions are discussed from the economics viewpoint; how the Central Electricity Generating Board (CEGB) decides which of its electricity generating stations to run to meet the demand for electricity at any point in time; and how the CEGB analyse possible future investments in new generating capacity. These questions are considered generally and then with the particular case of the proposed Sizewell B PWR reactor in mind. The cost of producing electricity has three components, the capital cost, the fuel cost and operating cost. These must be considered using meaningful and comparable figures. (U.K.)