What are the real-world loads and efficiencies of domestic hot water (DHW) systems in multifamily buildings? New Ecology, Inc. has tested many DHW systems using data loggers and Btu meters, and used these data to inform the design of new and upgraded DHW systems. Testing has determined tenant usage patterns, system efficiencies and issues with controls and system components. We’ll dig into hourly DHW usage profiles, the efficiencies of different gas-fired systems and ASHRAE DHW sizing methodology. Finally, we will explore the ways that these data have informed equipment recommendations and system design for multifamily buildings.