Electrical demand due to on/off thermostatically controlled loads

The integrated demand due to a group of similar on/off loads, each switched by thermostat, e.g. electric space heaters, is obtained as a function of the load-cycle time and the electricity authority´s registration period. Staggered switching from the cold-start condition must be adopted so that the maximum demand is determined by the steady-state cycling conditions. Subsequent demand perturbations due to failure of individual processes may be insignificant, although demand control will be necessary for the introduction of large blocks of power to the load. The variance of the demand may be decreased by a reduction of the cycle time, thus leading to closer demand control, and hence to economies in the maximum-demand tariff.