Abstract: A control unit for a temperature regulating system for heating or cooling a space includes an analog network, responsive to various variable environmental factors and simulating various fixed environment or building factors, is connected to a condenser to charge it. A predetermined voltage represents the desired temperature and is measured by a voltage sensor which is connected with circuitry for calculating rapidly the time needed for the system to be "on", whereby, for example, needed heating time is determined in a fraction of the actual time.