California Residential Methane Emissions Characterization (CARMEC)
Research will improve California’s methane emission inventory, quantify benefits of building decarbonization and inform the development of cost-effective strategies to reduce methane emissions from residential buildings.
Lawrence Berkeley National Laboratory
Recipient
Berkeley, CA
Recipient Location
9th
Senate District
14th
Assembly District
$762,051
Amount Spent
Active
Project Status
Project Update
The project has compiled an extensive database of existing information (for Task 2: Synthesize Existing Information and Identify Data Priorities) and used that to prioritize new data collection. The database includes measurements made by teams from LBNL, Stanford University, PSE, and University of Illinois Urbana-Champaign (UIUC) that were collected with methods that were reviewed for validity and accuracy. The research team inter-compared the measurement methods used previously and selected the most robust and flexible for use in this study and adapted them for use with clothes dryers, outdoor grills, and pool heaters among the appliances not measured previously. The first Technical Advisory Committee meeting for the project was held on May 31, 2024.
Field work for this project started in the fall of 2024 and has continued since then with major sampling campaigns so far in Chico/Redding and Merced. As of July 2025, the project has measured emissions from one or more sources in 61 homes. Methane leaks have been quantified from 49 whole-house measurements, 47 meter + regulator sets, and pilot burners of 60 appliances. Transient and steady burner emissions have been measured from 119 appliances including 93 burners on 43 cooktops, 16 ovens, 17 packaged furnaces, 5 wall furnaces, and 29 burners on 9 outdoor grills.
The Issue
Leakage of fossil gas from infrastructure and appliances within residential buildings releases methane, which has a warming effect 25 times as potent as carbon dioxide over a 100-year time horizon. Methane leakage occurs when equipment is off (quiescent or resting conditions), when burners start and stop, and during steady burner operation. Emissions during resting conditions and during steady burner operation were measured in a pioneering study led by Lawrence Berkeley National Laboratory (LBNL, Recipient) with help from Richard Heath & Associates, Inc. (RHA). In a previous study, the Recipient and RHA measured emissions from 75 houses located throughout coastal and central California and from over 100 appliances in the homes. Subsequent studies have measured emissions during start/stop events, steady burner operation, and in some cases also resting emissions for hundreds of burners on various types of fossil gas appliances in California, Boston, Illinois, Indiana, and New York. These studies have consistently found that methane emission rates are highly skewed, which means that overall emissions from the population are driven by very high emissions from a small fraction of the homes and appliances. The skewed nature of the emission distribution means that an accurate estimate of the overall emission inventory requires more robust data about the frequency and magnitude of high emission equipment. Knowledge of the factors that predict or are associated with high emissions could be used to develop cost-effective programs to identify and replace high-emitting equipment. Accurate emissions data are also important for quantifying the expected benefits of policies that accelerate replacement or avoidance of older gas infrastructure, e.g., through retrofits. Critical deficiencies in the data that have been collected to date limit knowledge of overall methane emissions from the residential sector and the best approaches to reducing these emissions.
Project Innovation
The project will quantify and elucidate the sources of methane emissions from post-meter fossil gas infrastructure in California’s residential sector. The foundation of the study is a field sampling campaign in a large and diverse sample of homes that include owner- and renter-occupied houses and multifamily units in several areas of the state, focusing in the first year of field work on Chico, Redding, and Merced. The study is synthesizing methane emissions data that have been collected previously in homes and using data collected through the SUMMATION study of methane emissions in Bakersfield. The study will greatly expand and improve the quality of available data on emissions from residential gas distribution systems and equipment used for space heating, water heating, cooking, clothes drying, aesthetics, and leisure. Data collection and analysis aims to identify building, appliance technology, and household characteristics that can be used to screen for high emissions to design efficient programs to quantify and reduce state’s methane inventory.
Project Goals
Project Benefits
This project will result in the ratepayer benefits of lower costs and increased safety by providing the data and analysis needed to improve cost-effectiveness of programs designed to reduce methane emissions.
Safety
Enhances safety by improving understanding of where and how methane leaks occur in residential systems, enabling targeted maintenance and mitigation strategies that reduce the risk of gas accumulation, fires, and explosions in homes.
Affordability
Support quantification of the costs associated with methane leaks in residences.
Environmental Sustainability
By identifying and reducing methane leaks in California homes, the project will help lower greenhouse gas emissions and co-pollutants such as nitrogen oxides that contribute to smog and poor indoor air quality. This supports healthier living environments, particularly for residents in disadvantaged communities.
Key Project Members
Brett Craig Singer
Wanyu Rengie Chan
Subrecipients
The Regents of the University of California, on behalf of the Berkeley Campus
Richard Heath and Associates, Inc.
Stanford University
Physicians, Scientists, and Engineers for Healthy Energy
Match Partners
U.S. Department of Energy
