Quantifying Greenhouse Gas Emissions and the Marginal Cost of Carbon Abatement for Residential Buildings under California's 2019 Title 24 Energy Codes.

California's building energy codes (Title 24, Part 6), updated triennially since 1978, are the most stringent in the nation. The aim of California contemporary energy policy in general, and the state's building codes and standards in particular, is the reduction of greenhouse gas emissions. The state has identified residential designs that "bring value to the grid" as a key constituent of this effort. This research quantifies the marginal costs that code requirements add to new residential construction, the quantity of carbon emissions and abatement expected at a statewide level, and the marginal abatement cost of homes built under the new 2019 standards relative to those built under the prior code. We model hourly energy consumption and emissions (2020-2050) for seven residential building types representative of California production housing for each of California's 16 climate zones. Costs and benefits of each housing type are analyzed under a 30-year timeframe. Our results indicate that the 2019 code allows for a wide range of emission profiles, including very high long-term emissions resulting from the use of natural gas and under high leak rates. The significant and previously unreported impact of pre-meter natural gas leaks emphasizes the challenges that natural gas creates with respect to meeting California's long-term GHG reduction goals. Marginal abatement costs are dependent on natural gas leak rates, but consistently indicate that all-electric homes represent the first-best policy option for residential sector GHG abatement in California.