Abstract: A control apparatus for controlling the generators of a multiple steam generator or multiple hot water generator installation. The control apparatus includes burner command apparatus which limits each of the generators to one of at least two different maximum firing rate levels. The command apparatus is controlled by a data storage device, such as a microcomputer, which periodically adjusts the maximum firing rate level of the generators in accordance with the predicted loads of the installation. The firing rate of the generators is controlled by modulating apparatus which varies the firing rate within the maximum firing rate levels in accordance with the actual measured installation load. By controlling the actual firing rate in response to both the predicted and the actual installation loads, efficiency of operation may be optimized.