Lawrence Berkeley National Laboratory

California requires all new residential buildings to meet near-net zero energy building (near-NZEB) targets in its building energy efficiency standards (Title 24) starting January 2020. For the first time, rooftop solar PV is required in new homes under three stories tall. While individual technologies are available for energy efficiency and renewable energy, significant challenges exist for scaling up NZEB homes across the State of California. This study presents a novel and holistic modeling and cost-effective analysis of new single-family homes in California to inform the design of cost-effective near-NZEB homes, as well as to guide future updates of Title 24. California's NZEB homes are defined using the time dependent valuation methodology to evaluate their cost-effectiveness. A comprehensive set of energy efficiency measures, solar PV, and battery storage are considered in the modeling and analysis as well as different net-metering policies for rooftop PV compensation rates for exported power. The BEopt tool with the EnergyPlus simulation engine is used to model and optimize, based on cost, the building designs for all-electric and mixed-fuel single-family homes across all 16 California climate zones. Results show that optimal designs of near-NZEB single-family homes have lower lifecycle costs for both all-electric and mixed-fuel cases in all California climate zones than the 2020 baseline code-compliant homes. Cost-optimal designed all-electric homes are comparable in lifecycle costs to mixed-fuel homes in most climate zones in part because no natural gas infrastructure is needed. For battery storage, electricity rates with a greater degree of time-dependence will improve cost-effectiveness of near-NZEB or full NZEB homes. These findings provide technical and investment insights into the scale up of cost-effective near-NZEB home design in California. The methodology and models can be adopted for other U.S. states or international cities to inform policy making and design of near-net zero energy residential buildings.