Evaluating the Energy Savings From Community Scale Solar Water Heating in Los Angeles County: Residential Case Studies

Estimation of Energy Savings from Community Scale Solar Water Heating in Los Angeles County explores the extent to which community scale solar water heating systems, designed for residential structures in Los Angeles County and constructed from currently available technology, can displace natural gas for domestic water heating through a series of case studies. The effects of policy, urban form, and building characteristics on the performance of solar water heating systems, as well as community scale solar water heating’s potential to reduce emissions from the residential housing sector, are discussed herein. Three public and three private residential developments were selected as case studies for community scale solar water heating, with numbers of units and residents ranging from the tens to hundreds. These six cases were draw from the pool of approximately 19,000 “energy communities” in Los Angeles County, i.e. residential developments where the installation and operation of community scale solar water heating systems is broadly feasible. The six properties were also chosen to represent a cross-section housing stock and development patterns common in Los Angeles County, and different levels of suitability for solar water heating. The performance of and energy savings from solar water heating systems on each of these properties is then evaluated using the National Renewable Energy Laboratory’s System Advisor Model (NREL SAM). The results of the system simulations reveal how building characteristics and hot water demand affect the performance of community scale solar water heating systems. The case study sites’ system simulations show that residential developments with community scale solar water heating systems reach an average solar fraction of 50%. The results of the case studies indicate that community scale solar water heating is viable as an emissions reduction technology for the residential building sector in Mediterranean climates. However, side-by-side comparison with solar PV systems and other water heating technologies (such as grid-connected heat pumps) is necessary to determine optimality in terms of cost, emissions reduction, and thermal efficiency) in specific contexts.