1. An environmental control system for reducing the peak demand in electrical power required by controlling the environment within a plurality of zones within a building with a plurality of heating, ventilating and air conditioning units, comprising: a plurality of controllers for controlling the plurality of heating, ventilating and air conditioning units within the plurality of zones within the building, respectively; each of said plurality of controllers including a temperature sensor connected to a thermostat control for measuring a measured temperature within each of the plurality of zones within the building, respectively; each of said plurality of controllers having a desired set point temperature for generating a delta value representative of the temperature difference between said desired set point temperature and said measured temperature within the plurality of zones within the building, respectively; each of said plurality of controllers having a maximum delta value limit; a link interconnecting said plurality of controllers into a network; each of said plurality of controllers altering the operation of said thermostat control within each of the plurality of zones within the building by way of a preferred first non-overlap mode and a less preferred second overlap mode and a least preferred third demand saver setback mode and in accordance with the operation of the remaining plurality of controllers interconnected by said link to reduce the peak demand in electrical power required by operation of all of the plurality of heating, ventilating and air conditioning units; said preferred first non-overlap mode of operation for preventing the simultaneous actuation of multiple heating, ventilating and air conditioning units and for actuating a selected one of said controllers having the greatest delta value; said less preferred second overlap mode of operation for permitting simultaneous actuation of multiple heating, ventilating and air conditioning units for said controllers having a delta value exceeding said maximum delta value limit; said least preferred third demand saver setback mode of operation for raising said desired set point temperature of all of the plurality of controllers within the plurality of zones within the building thereby lessening the environment requirements within the plurality of zones within the building to reduce the need to simultaneous actuate multiple heating, ventilating and air conditioning units.