Development of Standardized Domestic Hot Water Event Schedules for Residential Buildings

The Building America Research Benchmark is a standard house definition created as a point of reference for tracking progress toward multi-year energy savings targets. As part of its development, the National Renewable Energy Laboratory (NREL) has established a set of domestic hot water events to be used in conjunction with sub-hourly analysis of advanced hot water systems. In certain applications (including analysis of recirculation loops, distribution losses, tankless gas water heaters, and solar hot water systems with load-side heat exchangers) energy use can be strongly affected by event flow rate, duration, frequency, clustering, and time of occurrence. High-level constraints on mains temperature and average daily hot water use, along with detailed event characteristics derived from past research and a software tool developed by Kassel University in Germany, were used to generate hot water events over one year for houses of different sizes in various locations. The events were established in 6-min increments for showers, baths, sinks, clothes washers, and dishwashers. Flow rates and times of occurrence varied randomly based on specified probability distributions. The final event schedules reflected the same daily variability as an actual household, thereby providing more realism to energy simulations involving advanced water heating systems.