A system for controlling the voltage of an electrofilter of the type which, after a voltage breakdown, substantially reduces the magnitude of the electrofilter voltage. After a predetermined deionization time, the filter voltage is raised to a new level which is lower than the filter voltage at which the initial voltage breakdown occurred, by a predetermined amount. The filter voltage is subsequently raised in accordance with a predetermined voltage-time function until a further voltage breakdown occurs. The electrofilter voltage is controlled by a microcomputer system in accordance with stored control parameter values. The stored control parameter values are advantageously recalled to control the electrofilter voltage in response to the operating state of a plant in which the electrofilter is employed. In plants wherein a plurality of electrofilters are employed, each such electrofilter is controlled by an associated microcomputer system, the plural microcomputer systems being controlled by a central pilot computer. The central pilot computer of the plant computes strategies which enhance the energy efficiency of the overall electrofilter purification system.