According to recent figures from Architecture 2030, U.S. carbon emissions today are down 23 percent from 2005 levels. The country’s largest energy consumer, the building sector, has reduced emissions 30 percent below 2005 levels. As the building design and construction industry continues to advance low-carbon solutions that tackle both operational and embodied carbon, a looming challenge remains: our national electrical grid still emits a lot carbon into the atmosphere.
Exactly how much carbon is emitted per unit of electricity will vary widely from one state to another. The figure and table below illustrates the grid's carbon intensity per unit of energy per state. Measured in pounds of carbon dioxide per kilowatt-hour (lb CO2 / kWh), the average for the country is 0.919. This means that just under one pound of carbon dioxide is emitted for every kilowatt-hour of electricity generated in the U.S. Three years ago, the U.S. average was precisely 1.000 lb CO2 / kWh. So, there has been a marginal improvement.
Figure: Carbon dioxide emissions per kilowatt-hour of electricity generated per State, including the District of Columbia.
The building design and construction industry is abuzz with the notion of total electrification. This is grounded by a simple premise: in theory, the electrical grid can become 100 percent green (i.e., zero carbon emissions impact) and using fossil-fuel energy sources will inherently always have a carbon emissions impact.
In the long-term, electrification makes sense; it is the key to eliminating operational carbon from the building sector. However, if a team has a project today in a part of the U.S. where the grid carbon intensity is quite high, it will become more challenging to realize the dramatic near-term reductions in carbon emissions that we need to achieve across the entire building sector to avoid the worst-case scenarios as presented by the recent summary report from the IPCC.
Table: Carbon dioxide emissions per kilowatt-hour of electricity generated per State, including the District of Columbia.
Carbon dioxide factors vary considerably by fuel source. For instance, according to the U.S. Energy Information Administration (EIA), the pounds of CO2 emitted per million British thermal units (BTUs) produced is as follows:
- Natural gas: 117.00 pounds
- Propane: 139.05 pounds
- Coal (bituminous): 205.70 pounds
The Biden administration has pledged to achieve a clean electrical grid by 2035; however, projections suggests that such rapid decarbonization of our electrical grid will be a challenge. According to the NREL's 2020 Standard Scenarios Report, models indicate that renewable energy resources will see substantial growth but in all scenarios; but natural gas, oil, and coal will remain a part of the U.S. electrical grid for the foreseeable future. Resources for the Future's Global Energy Outlook 2021, which aggregates 16 scenario types, similarly finds that fossil fuels will be a part of the global energy mix for decades to come.
If immediate action is required now regarding low/no-carbon buildings, we need a multifaceted, comprehensive approach to greening our buildings and our infrastructure. A project in a State with high grid carbon intensity should aggressively reduce grid-based loads as much as possible. NREL's Cambium tool, EPA's eGRID resource, electricityMap, and WattTime are helping teams to process past, present, and future data about grid carbon intensity and the progress of greening the electrical grid.
The grid will not become green overnight; but we have the information and resources today to implement a data-driven approach to ensure that the building sector continues to decarbonize as quickly and effectively as possible.