In California, approximately half of all residential gas consumption is used to heat water, and nearly 90% of all residences have gas water heaters. While water heating represents a relatively small portion of total residential energy use (approximately 3%), annual CO2 emissions from gas water heaters are comparable to those produced by a city of 700,000. Reducing the carbon intensity of residential hot water heating can yield considerable energy savings, and solar thermal technology is an appealing alternative for doing so sunnier parts of the state.

The goal of this project is to evaluate the energy savings from community-scale solar water heating in Los Angeles County, and provide insights into the costs and benefits of approaching the de-carbonization of residential water heating from a supra-domestic scale. The estimation of energy savings involves three steps, and leverages data from the UCLA Energy Atlas:

1. Selection of solar thermal technologies for a community scale solar water heating system in LA County based on cost and performance criteria.

2. Modeling of demand to estimate the volume of gas currently used to heat water. Demand profiles will be scaled by the age and size of the residence using account-level data from the Energy Atlas.

3. Modeling the performance of the solar thermal systems designed in Step 1 using solar potential data for LA County.

4. Selection of case study sites based on urban form, socioeconomic factors, and availability of rooftop space.

5. Estimation energy savings using methods developed in Steps 2 and 3 for each case study site.

The energy savings estimated in each of the case studies will help to assess how effective a community scale approach to solar water heating is in reducing emissions from the residential building sector. Additionally, examining the deployment of community scale systems in specific cases will yield valuable information about the feasibility of such an approach in Los Angeles County, and the contexts in which a community scale approach is most beneficial.

Poster presented by Robert Cudd at American Solar Energy Society Solar Conference 2018.