Emissions Estimates for 100 million properties across the United States

Emissions Estimates for 100 million properties across the United States

Across the country, local and state governments are starting to discuss and implement laws aimed at reducing the greenhouse gas emissions associated with buildings. States are beginning to adopt building codes to promote energy efficiency standards and tax and rebate incentives at the federal and state level are encouraging homeowners to improve home energy efficiency with heat pumps and other technology. In New York City, Local Law 97 imposed efficiency and emissions standards on most large buildings starting in 2024, with tighter regulations coming into force in 2030. Lawmakers in Chicago are considering a bill that would ban the use of natural gas in new constructions across the city.1At the federal level, new energy efficiency standards for gas and electric appliances were recently announced.2These efforts seem to be accelerating; according to the National Caucus of Environmental Legislators, at least twenty-four states introduced building decarbonization regulations in 2023.3

To understand the implications of these sorts of regulations - and identify priorities for reducing emissions - it is important to first understand patterns of building-related emissions across the country. The first piece in this seriesdiscussed ICE Sustainable Finance's estimates of energy usage for the over 100 million U.S. households in ICE's property data records via the acquisition of Black Knight. Here, in Part 2, ICE Sustainable Finance shows how energy usage estimates are converted into greenhouse gas emissions estimates by taking fuel efficiency and electricity grid fuel mix information into account. Large-scale trends in emissions across the country are affected by several interacting factors, including climate, household heating and cooling needs, on-site fuel sources, and the electricity grid fuel mixes.

How much carbon equivalent do U.S. households emit?

Across the United States, ICE Sustainable Finance estimates that the median annual greenhouse gas emissions for single family detached and single family attached homes4is equivalent to 8,600 kg CO2. This is a significant amount of greenhouse gas; to put it into context, a return flight from London to New York generates about 986 kg CO2per passenger, about one eighth the equivalent annual emissions of the median single-family home.5

In terms of geographical variation in emissions, the highest median emissions tend to be in the midwestern U.S., and the lowest emissions in the Pacific Northwest, Hawaii, and California (Figure 1). States with lower median emissions generally have milder climates, which translates into less need for heating and cooling individual households.

Total residential emissions can be broken down into Scope 1, the emissions due to energy produced on-site, and Scope 2, emissions due to energy that is produced offsite from the electricity grid. Median Scope 1 residential emissions are highest in northern states (Figure 2) where many households rely on fuel oil, natural gas, and propane for home heating, rather than electricity.7By contrast, in states in the South like Florida, Georgia, and Alabama, fuel sources that produce energy onsite are relatively rare, and electricity is commonly used for home heating. As a result, the median Scope 1 emissions for southern states like Florida, Georgia, and Alabama are negligible compared to the rest of the country. (The reasons behind the geographical variation in the dominant fuel sources used for home heating across the United States are discussed in Part 1of this series.)

Residential emissions that are not produced onsite but are sourced from the electrical grid are considered 'Scope 2.' Across the United States, electricity generated at more than 7,000 power plants is distributed to over 145 million customers through over 150,000 miles of power lines that form interconnected grids.8The day-to-day operation of these grids are controlled by over 65 regional balancing authorities covering different regions of the country (Figure 3). At any given time, a given balancing authority may be generating electricity with a different mix of fuel sources. Depending on the location of the balancing authority and its power generation capabilities, these fuel mixes could include (among others) hydroelectric, nuclear, solar, coal, natural gas, and wind, with relative contributions that many vary over time (e.g., Figure 4).

Because the fuel mixes used by balancing authorities change over time, Scope 2 emissions are generally more difficult to estimate than Scope 1 emissions. To estimate Scope 2 emissions for a given household, ICE Sustainable Finance must link three pieces of information together: (1) the energy usage of the household over time, estimated using the approach described in Part 1of this series, (2) the balancing authority managing the grid that delivers electricity to the household, and (3) the fuel mixes used by the balancing authority over time.

As a result of this complexity, Scope 2 emissions have a more varied pattern than Scope 1 emissions across the country. These patterns reflect not only the varying fuel source mixes of the balancing authorities discussed above, but also climatic differences and the relative reliance of households on electricity for heating and cooling (Figure 5). Scope 2 emissions are lowest in the Pacific Northwest and California-states with mild climates, less heating and cooling need, and significant amounts of renewable energy available to their balancing authorities-and the Northeast, where households rely heavily on onsite fuel sources for home heating. By contrast, Louisiana has some of the highest residential electricity usage and Scope 2 emissions, because much of its electricity is sourced from natural gas.10

Emissions intensities for electricity-the greenhouse gas footprint per unit of energy generated (kg CO2e per kwh of electricity)-further illuminate the important role that fuel mix plays in residential emissions across the country. Colorado, Wyoming, and Utah have low overall electricity usage (Figure 4 in Part 1), but relatively high emissions per kilowatt-hour. By contrast, Texas, Alabama, and Georgia have higher rates of electricity usage and lower emissions per kilowatt-hour.. Western Washington state has relatively high median energy usage overall (Part 1, Figure 1), but low emissions intensity due to the high reliance on renewable energy sources for electrical grids in the Pacific Northwest. (On January 11, 2024, Bonneville Power Administration, a balancing authoring covering much of Oregon, Washington, and Idaho, generated 57% of electricity from hydropower, 23% from wind, 12% from nuclear and 6% from natural gas.11)

The tools that power this analysis

To estimate residential emissions across the country, ICE Sustainable Finance uses information on the over 100 million residential buildings in ICE property records. For fuel sources combusted on-site (Scope 1 emissions), estimating emissions is relatively simple. Energy usage estimates (see Part 1of this series) are multiplied by a conversion factor to estimate the carbon dioxide equivalent.

Estimating Scope 2 emissions is more complex. ICE property records are used to associate every household with a balancing authority (though in some cases a single property may be located within several balancing authorities' regions of coverage). The fuel type mix used by balancing authorities across the country over time comes from Singularity, a company that provides open grid emissions data on an hourly basis for the conterminous U.S. Energy usage estimates described in Part 1of this series (in increments of 15 minutes) are rolled up to hourly estimates and matched to the electricity generation mix information over that same hour for the relevant balancing authority. Based on the fuel mix, an average emissions intensity per kwh (kg CO2e/kwh) can then be assigned to each residential property for that hour. The annual electricity (Scope 2) emissions for a property are calculated by multiplying the estimates of emissions intensity (kg CO2e/kwh) and electricity usage (kwh) every hour and summing those values over the year. Total emissions are the sum of Scope 1 and Scope 2 emissions.

In Part 3 of this series, ICE Sustainable Finance will focus on a subset of counties, examining the relationship between estimated energy usage and emissions in more detail.

Continue to part 3