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Battle over accuracy of EPA's eGRID carbon emissions estimator

Feb 10, 2016

The U.S. Environmental Protection Agency is defending its eGRID system against a critique by an analytics think tank.

Companies all across the U.S. use eGRID to calculate their own indirect carbon emissions based on how much electricity they use. And it's not uncommon to see a company brag about a) their transparency on emissions and b) their progress in reducing their indirect emissions to fight climate change. 

Say you're Google, and you want to tell people how much carbon one of your data centers puts into the atmosphere. You have to know how much of the electricity powering the center comes from coal, solar, wind, or  natural gas. The eGRID model is how you do that.

But eGRID recently came under fire from Lux Research. The analytics think tank says eGRID is inaccurate, because it divides the country into only 24 regions, when in fact the electrical grid is far more complex than that. Lux researchers also say eGRID is not updated very often; the latest information comes from 2012.   

Lux Research developed its own model, dividing the country into 134 regions, and they used current electric generation data that is available every month from the Energy Information Administration.

The firm claims its model improves the accuracy of carbon emissions estimates by a factor of 80. Using that model, Lux Research found that Google, for example, underestimated the percentage of coal-generated electricity at one of its data centers by 30%.  

While eGRID found that Amazon's 23 U.S. data centers drew 35% of their power from coal, the Lux Research model indicated it's closer to 43%.

Here is the EPA's response to what Lux Research said:

eGRID is a comprehensive database of the environmental characteristics of all grid connected electric power generated in the United States, providing researchers, policy makers and the public with a powerful set of information about electricity generation. For over 17 years, eGRID data have been widely used by EPA and others to quantify the air pollution from power plants as well as the benefits from reduced electricity demand. In addition, eGRID’s data on carbon dioxide emission rates are commonly used to estimate the indirect emissions from electricity purchases in most carbon footprint calculators and greenhouse gas inventories.

Re: timing of eGRID updates

eGRID has been collecting and synthesizing power sector data for over 17 years and the long-term and widespread use of eGRID ensures accurate benchmarking and meaningful comparisons over time. 

eGRID gathers data from all available sources – including annual data that is directly reported from power plants to the Department of Energy’s Energy Information Administration and EPA – and synthesizes these into a usable format. eGRID uses annual data to reduce the seasonal variability in generation and emissions. This data then undergoes extensive analysis, quality control, and peer review – analytical steps that take time but which result in a comprehensive, accurate and robust data set. EPA has begun implementing a series of data-handling improvements that will result in quicker releases of future eGRID updates. 

Re: number of subregions

eGRID provides emission factors at many levels (i.e., plant, state, and power control area (PCA). Given the interconnectedness of the electrical grid, however, EPA recommends using the emission rates from the 26 eGRID subregions. This level appropriately addresses power imports and exports and better represents the actual mix of generation types (e.g., renewable, natural gas, coal) used by individuals within the eGRID subregion.

Whew. That's a mouthful and a half for the EPA. And, because we love a good fight between geeks, we asked Ory Zik, vice president of analytics for Lux Research, to respond to the EPA's response:

When someone writes: “For over 17 years, eGRID data have been widely used by EPA and others” it does sound that it calls for modernization.

Is there any other data system in our lives that has not been modernized  for 17 years? Except, of course, the most important one: our carbon emissions!

We order food, taxis, perform ecommerce, book flights, every aspect of life uses modern data tools. Time for carbon analysis to do the same (unless of course we are determined to solve one of the most important 21st century problems with 20th century tools.

While Lux Research provides an energy benchmarking service to corporations for a fee, Zik tells us that the mathematical model the firm developed has been shared with the analytics community via a peer-reviewed publication – and the firm has also shown its model to the EPA, hoping to nudge it in the direction of modernizing eGRID.