SIGNAL: Marginal CO2
The Marginal Operating Emissions Rate (MOER) represents the emissions rate of the electricity generator(s) that are responding to changes in load on the local grid at a certain time.
Every time you use more electricity, that instantly causes a power plant to make a little more. But… which power plant? Usually, it’s a fossil fuel plant burning coal or gas, which is why using energy creates pollution. Yet as renewable energy keeps growing, there are more and more moments when using electricity instead only activates a clean power plant like wind or solar. To help people understand the emissions caused by when they use electricity and to help them cause fewer emissions, WattTime produces marginal emissions data and makes them available through an API.
What is it?
The Marginal Operating Emissions Rate (MOER) represents the emissions rate of the electricity generator(s) that are responding to changes in load on the local grid at a certain time. The MOER includes the effects of renewable curtailment and import/export between grid regions. The units of MOER are the amount of pollution per unit of energy (lbs/MWh).
How is it used?
The MOER can be used to make decisions that avoid the most emissions. IoT companies use the MOER forecast as an input signal to their device scheduling optimization, or to create a UI element advising users when to run appliances or plug in an EV. Renewable energy purchasers use the historical MOER to select a project that avoids relatively more emissions. In emissions accounting, the MOER is used to account for the avoided emissions of a project as described by the GHGP Project Protocol and the Guidelines for Quantifying GHG Reductions from Grid-Connected Electricity Projects.
Temporal coverage
- Granularity: 5 minutes
- Historical: At least 2 years in the past, published usually within 6 hours
- Forecast: +72 hours (rolling 3-day forecast), published usually within 30 seconds
- Forecast (Historical): At least 2 years in the past
Geographic coverage
- Granularity: MOER regions are typically balancing regions or subregions
- Coverage: Global (200+ countries & territories); MOER Signal coverage can be seen here
Methodology + validation
WattTime builds MOER models based on the empirical technique founder Gavin McCormick published in peer-reviewed academic literature. WattTime’s research group continues to develop the methodology to provide the most impactful and actionable signal possible with available data. WattTime recognizes that any MOER model needs to be validated in order to be confident that its use will reduce emissions. WattTime’s research team performs validation of each model it produces and leads an external coalition for improving the tools used for validating marginal emissions models.
Learn more about WattTime's methodology and validation.
Learn more about WattTime's methodology and validation.
FAQ
Does the MOER model include the effect of imports & exports? Yes, we trace the causal link to neighboring regions. The MOER data describes the emissions rates of generators responding within a region and/or outside that region in response to a load change within a region.
Why does <clean region> have such a high marginal emissions rate? While places like Sweden, Quebec, and British Columbia have exceptionally clean generation (dominated by Hydro), they exchange a lot of power with their neighbors, which rely on fossil generation to meet changes in demand. So, if power demand increases in Sweden, less of their Hydro will be available to export to neighboring countries, and that drop in exports will have to be met with an increase in dirty generation like coal or other fossil resources in the neighboring region. While Sweden itself is very clean, the effect of consuming more power within the region causes more emissions in neighboring regions. The MOER reflects this real-world cause & effect.
Does MOER include the effect of transmission & distribution losses on emissions? It only includes the effect of transmission losses. Since it is an empirical model that estimates the relationship between load and emissions from generation, it inherently includes the effect of all losses between the points where load is measured and where generator emissions are measured. Grid load is typically measured upstream of distribution infrastructure, so distribution losses are not included. The MOER has inherently accounted for the average transmission losses in a region, but the effects of varying transmission line length for specific locations within the region are not directly estimated.
Is the MOER a CO2 or a CO2e (equivalent) emissions rate? The unit is pounds of CO2 per MWh, not CO2e. For the power sector, the difference between CO2 and CO2e is usually small, between 0.3-0.5% for the non-CO2 GHGs from power plants. If you need CO2e, you can use a conversion factor from CO2, and we'd be happy to help you determine that.
Are any other lifecycle emissions included? MOER 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).
How does the MOER model incorporate the effect of curtailed renewables? WattTime estimates renewable curtailment based on historical reported curtailment from grid operators and ISOs, as well as grid congestion pricing patterns. This captures both system-level curtailment and subregional curtailment due to congestion. A good overview of how curtailment is estimated can be seen here.