The flow rate is an important factor for calculating and monitoring the energy consumption of systems such as wastewater treatment plants or cooling systems, which need to control the flow rate precisely for optimum operation. An excessively high flow rate leads to high energy consumption and higher costs. It is therefore important to adjust the flow rate so that it meets the requirements of the system. A frequency inverter can regulate the speed of a pump and thus control the flow rate of the medium flowing through the pipe. In this way, the flow rate can be adapted precisely to the requirements, which saves energy and improves the efficiency of the system.