Potential for Energy Savings Through Residential Hot Water Distribution System Improvements

Hot water distribution systems have received a great deal of attention recently, as residential energy efficiency programs target measures that can drive whole-house energy savings beyond the 50% level. Unfortunately, evaluating distribution losses and the resulting thermal interactions with space conditioning loads is very complicated, and must be performed using advanced simulation tools and realistic hot water event schedules, including appropriate event volumes, draw sequencing, and time between draw events. The authors developed a simplified methodology for the analysis of distribution losses based on detailed modeling of alternative system designs using HWSIM, a model specifically designed for this application. Curve fits were then applied to the results so they could be extrapolated to many different house designs and climate regions. The authors also performed preliminary analysis of whole house energy effects of alternate hot water distribution systems in two climates.