Fluids from their earliest days have great significance because it is almost impossible to imagine life without them. As it is impossible to imagine life without them, it is necessary to know and measure fluid flows. Fluid delivery is crucial for a more comfortable life for the population of each region and it is essential to minimize transportation and delivery losses to a minimum or to zero. It is important to measure the flow of fluids flowing through pipelines that are not the ideal cross-section of the surface at all positions throughout its length, and this is where physical changes and losses occur. The paper defines physical quantities related to fluid flow and sets up a physico-mathematical model on the basis of which it is possible to determine system parameters and respond in a timely manner to possible losses. Different methods of flow measurement are described, which are described and graphically presented from a theoretical point of view, so that, at the end of the paper, two different flow meters can be used and the techno-economic analysis analyzed in the practical chapter. Flow meters are devices that are indispensable for industry, households, and generally the supply of water, gas and other media. It is impossible to imagine the production process of supplying heating to a part of households from a heating plant where the flow will not be measured because the system is unattended. The use of a flow meter is shown where, with the prior agreement and permission of Tehnostan d.o.o. accessed a thermal substation in the veterans building on Hrvatsko zrakoplovstvo street. The building is connected to the main heating plant in Borovo naselje and has hot water circulation throughout the year. The Siemens RVD250 calorimeter and the Micronics U1000-HM portable ultrasonic flowmeter were used to measure hot water flow. No greater deviations where found then allowed by the manufacturer. Techno-economic analysis has determined the advantage and cost-effectiveness of ultrasonic flow meter over electromagnetic.