AbstractR290 is one of the most promising refrigerants for heat pumps and cooling processes working in a temperature range of –15 to 70 °C. The nearly neglectable global warming potential and attractive thermodynamic properties allow the design of climate‐friendly and efficient refrigeration systems and heat pumps. However, R290 is flammable, and the use of charge‐reduced components and designs should be the first central step to reduce safety risks. Whereas the prediction of heat capacity, temperatures and pressure drops are sufficiently precise the prediction of refrigerant charge is not very accurate when using computer‐aided design tools. The article presents a method to enhance accuracy for refrigerant cycles with less than 500 g of R290.