LME Frequently Asked Questions

You’ve got questions; we’ve got answers. Skip to a section below:

General Questions

Use and Implications

Technical Questions

General Questions

1.     What do Locational Marginal Emissions (LMEs) measure?

LMEs provide a rate (tons/MWh) of carbon impact for electricity generation or consumption at a given location in the grid, hour-by-hour. That hourly rate is used to accurately measure the amount of carbon dioxide equivalent (CO2e) avoided by each MWh generated by a clean energy project. It is also used to accurately measure the amount of carbon dioxide emitted as a result of each MWh consumed by load.


2.     How does REsurety’s LME data compare to other carbon emissions tools?

REsurety’s LME data is the first and only carbon intelligence product available that enables project-specific granularity. To date, carbon impact measurement tools have relied on regional averages, which can materially over- or under-estimate the carbon impact of a specific clean energy project. By way of example, REsurety and The Brattle Group’s whitepaper highlights a west Texas solar project that abates less than half of the carbon as a neighboring west Texas solar project due to local transmission constraints. Unlike other carbon emissions tools, REsurety’s granular LME data surfaces those critical project-specific carbon impact details.


3. How do I access REsurety’s LME data?

REsurety provides access to LME data and LME-driven carbon impact intelligence through two product options: 1) Project Reports, and 2) API access. A Project Report provides the historical carbon impact of a specific generation project or load facility as well as the key drivers of that impact, such as timing of generation and grid congestion. The API product provides direct access to the hourly LME rates for all resource nodes in a given ISO. REsurety’s Project Reports product is available today. REsurety’s API product will be released later in 2021.


4. In what location and for what periods are LMEs available?

Today, LME data is available in ERCOT. LME data for PJM and CAISO will be available in the coming months with other markets to follow. In ERCOT, LME data is available with hourly, project-level granularity from January 2018 through the present, with a ~60 day lag.

Use and Implications

1.     How do LMEs support my sustainability goals?

LME data empowers you to go carbon neutral confidently and efficiently. 

Go carbon neutral confidently. Before LME data, sustainability-focused decision makers could only hope that regional averages accurately reflected the carbon impact of their specific load facilities and clean energy generation projects. With LME data, you can now confidently measure the carbon impact of your specific facilities and projects, dramatically improving your confidence in your carbon footprint. 

Go carbon neutral efficiently. Armed with accurate intelligence on your current carbon footprint, LME data enables sustainability decision makers to maximize the carbon impact of future load siting and clean energy procurement decisions by identifying the locations and projects with the greatest relative decarbonization potential. 


2.     What are the implications for storage?

LMEs empower energy storage operators to measure the specific carbon impact of their planned or existing projects, whether stand-alone or co-located with a clean energy generation facility. Due to the high volatility of carbon intensity node-by-node and hour-by-hour, energy storage operations can materially increase or decrease the carbon intensity of the grid.  For the first time, LME data makes accurately measuring that carbon impact a reality. 


3.     What are the implications for transmission?

LMEs can help identify the carbon impact of transmission bottlenecks. By measuring the amount of incremental carbon caused by each transmission bottleneck, we can better understand the emissions benefit of new transmission investments.

Technical Questions

1.     How does REsurety calculate LMEs?

Every megawatt-hour (MWh) of clean energy injected into the grid displaces another megawatt-hour of electricity that would have otherwise been produced. The generator or group of generators whose production was displaced by that incremental injection of clean energy is referred to as the “marginal generator(s)”. REsurety’s algorithm uses grid and market data to identify the marginal generator(s) for each electrical node and each hour and then calculates the quantity of carbon avoided as a result of the marginal generator(s) reduction of production. For load, the same concept is applied but the sign is flipped: marginal generator production (and associated emissions) is increased as a result of the incremental increase on energy consumption.


2. Why does granularity matter?

Because the carbon impact of clean energy varies by location and by hour, annual or regional averages don’t capture the specific carbon impact of individual clean energy projects or loads. We use granular market data to identify the contribution of marginal generators relative to each project location and given the conditions of the grid in each hour.


3.     Why does project location matter?

Clean energy projects located in different parts of the grid, even within the same region or zone, can have wildly different carbon abatement impacts. This happens because transmission bottlenecks affect the mix of resources displaced by incremental clean energy generation. For example, clean energy generated on one side of a transmission constraint may displace generation from a coal plant – resulting in very high carbon abatement. However, clean energy generated on the other side of that transmission constraint may cause the curtailment of solar project – resulting in no carbon abatement.


4.     Why does timing matter?

Clean energy generated in one hour may have a very different carbon impact than clean energy generated in a different hour, even at the same location. This happens because the state of the power grid varies dramatically hour-by-hour as renewable project generation varies with the weather, non-renewable generators ramp production up or down in order to match load, and the distribution of load on the grid changes as people go about their day. All this means that the marginal units – the specific units that would be displaced by a MWh of clean energy produced at a particular location – change hour-by-hour. For example, during a blustery hour in the panhandle of Texas the marginal generator is often another wind project, meaning an additional MWh of clean energy generation in the panhandle would have no impact on carbon emissions. However, as soon as the wind dies an incremental MWh of clean energy would displace a coal or gas plant, causing significant carbon abatement.

Read More

WHITE PAPER: Locational Marginal Emissions

Purchasing renewable energy is a means decarbonization, but renewable energy projects are not all equal when it comes to cutting carbon. Locational Marginal Emissions (LMEs) measure carbon emission avoided by renewable energy projects at the most granular spatial level: the electrical node where energy is injected into the grid.