Abstract: With an air conditioning system a plurality of building areas, for which individual energy accounts have to be rendered, are supplied by a common fresh air supply and cooling installation. The volume flow rates are controlled by one volume flow rate regulator each, the setpoint of which is adjustable through a servomotor. An output signal representing the setpoint of the volume flow rate regulator is generated and is applied to a meter. This provides with sufficient accuracy the distribution of the volume flow rates between the various building areas as a base for the accounting and billing of energy expenses.