SIGNAL: Average CO2
The Average Operating Emissions Rate (AOER) is a calculation of the average emissions rate of all the electricity generated on the local grid at a certain time.
What is it?
The Average Operating Emissions Rate (AOER) is a calculation of the average emissions rate of all the electricity generated on the local grid at a certain time. Average emissions generally are a way to allocate responsibility for emissions evenly, instead of causally. The units of AOER are the amount of pollution per unit of energy (lbs/MWh).
How is it used?
Load shifting using this signal wouldn’t reduce emissions, but many companies find the data helpful for the purpose of attributional emissions accounting. GHG Protocol’s Corporate Standard allows the use of average emissions factors to determine the total annual emissions footprint of the electricity consumption of a company’s assets. The AOER allows this accounting to be done using more recent and frequent emissions factors. Learn more about why marginal emissions are better than average emissions for impact accounting.
Temporal coverage
- Granularity: Hourly
- Historical: At least 2 years, published within 72 hours
- Forecast: None
Geographic coverage
- Granularity: AOERs are typically reported at the balancing region or country level
- Coverage: WattTime’s AOER Signal coverage can be seen here
Methodology + validation
The AOER is calculated by summing the total emissions from all generators in a particular hour and grid region, and dividing by the total energy generated (MWh). WattTime performs a simple calculation using publicly available data sources.
Step 1: Determine total generation for each fuel type (e.g. use EIA data or similar).
Step 2: Assign annual emissions factors for each fuel type (e.g. use IEA annual factors by country).
Step 3: For each fuel type, multiply its total generation (MWh) by its annual emissions factor (lbs/MWh) and sum the results to get the total emissions (lbs); then divide total emissions by total generation to get the AOER (lbs/MWh) for the grid.
Step 1: Determine total generation for each fuel type (e.g. use EIA data or similar).
Step 2: Assign annual emissions factors for each fuel type (e.g. use IEA annual factors by country).
Step 3: For each fuel type, multiply its total generation (MWh) by its annual emissions factor (lbs/MWh) and sum the results to get the total emissions (lbs); then divide total emissions by total generation to get the AOER (lbs/MWh) for the grid.
FAQ
Are AOER data “consumption-based” or “generation-based” factors? WattTime’s AOER is a generation-based factor, which means it is specific to generators within a particular grid region and does not reflect imports/exports with other neighboring regions.
Does AOER include the effect of transmission & distribution losses on emissions? No. Since it is a generation-based factor, it reflects the emissions per unit of energy generated.
Is AOER measured in pounds of CO2 or pounds of CO2e (equivalent)? The unit is pounds of CO2 per MWh, not CO2e. It does not incorporate an estimate of the (relatively small) contribution from the emissions of CH4 and N2O from combustion for electricity generation.
Are any other lifecycle emissions included? AOER includes operating emissions only. These are the direct CO2 emissions from combustion for electricity generation. Any other upstream or downstream emissions are excluded (e.g., from fuel extraction and transportation).