Probability theory description of domestic hot water and heating demands

The paper presents the methodology for the risk-based dimensioning of domestic hot water (DHW) and heating demands. It is demonstrated that they are stochastic variables. DHW demands are specified on the basis of hot water consumption statistics in Hungary. The standard values of heat demands for heating are based on the duration curve of external air temperatures. This study discusses daily mean temperature distribution in the heating season - between 15 October and 15 April in Hungary - and the description of its duration curve sorted by time. The authors verify the assumption that the duration curve can be described by normal distribution mathematically with high precision. Thereby they somewhat put an end to the process of mathematical experimentation on what function should be used to describe the frequency and duration curve of external daily mean temperatures in the heating season.