The analysis of these systems is similar to the water heating systems presented in Chapter 5. When both space heating and hot water are considered, the rate of the energy removed from the storage tank to load (Ql) in Eq. (5.31) is replaced by Qls, the space load supplied by solar energy through the load heat exchanger, and the term Qlw, representing the domestic water heating load supplied through the domestic water heat exchanger, is added, as shown in the following equation, which neglects stratification in the storage tank: