What the EPA eGRID CO2 numbers mean

The EPA's eGRID database publishes the average amount of carbon dioxide released per megawatt-hour of electricity generated in each state. The number is measured in pounds of CO2 per megawatt-hour (lbs/MWh). A state with a lower number means its power grid produces electricity with less carbon pollution than a state with a higher number — usually because it relies more on wind, solar, nuclear, or hydroelectric power instead of coal and natural gas.

These numbers change year to year because the mix of power sources on each grid shifts. A state might add wind farms, retire coal plants, or experience drought that reduces hydroelectric output. The 2021 and 2022 eGRID reports reflect those real changes in how electricity was actually generated during those years.

The EPA publishes eGRID data to help utilities, researchers, and individuals understand the carbon footprint of electricity. If you are calculating the emissions from your own electricity use, or comparing the climate impact of different states, these state-level averages are the standard reference.

Key Takeaways

  • eGRID CO2 rates are measured in pounds of CO2 per megawatt-hour and reflect the average carbon intensity of each state's power grid.
  • States with lower rates typically use more renewable energy or nuclear power, while states with higher rates rely more on coal and natural gas.
  • The 2021 and 2022 rates differ because power generation sources change year to year based on new plants, retirements, and weather.
  • You can find the specific 2021 and 2022 state rates on the EPA eGRID website, which publishes data by state and by power plant.

How the EPA calculates these numbers

The EPA collects data from power plants across the country on how much electricity they generated and how much CO2 they emitted. For each state, eGRID divides total CO2 emissions by total electricity generated to produce an average rate. This is a straightforward calculation — it reflects what actually happened on that grid during that year, not a projection or estimate.

The data comes from the Emissions & Generation Resource Integrated Database, which tracks nearly every power plant in the United States. Plants report their fuel type, fuel consumption, and emissions to the EPA and other agencies. eGRID consolidates this information and publishes it by state, by power plant, and by utility.

One important detail: the eGRID rate for a state includes all electricity generated within that state's borders, regardless of where it is consumed. Some states generate far more electricity than they use and export the rest to neighboring states. This means the rate reflects the carbon intensity of generation, not the carbon intensity of consumption in that state.

Why the rates changed between 2021 and 2022

Most states saw their CO2 rates shift between 2021 and 2022, though the direction and size of the shift varied. States that added renewable energy capacity typically saw their rates decline. States that experienced drought or other weather events that reduced hydroelectric output typically saw their rates rise. States that retired coal plants saw larger declines.

Natural gas prices and availability also influence the mix. When natural gas is expensive or scarce, utilities may run coal plants more often, raising the CO2 rate. When natural gas is cheap and plentiful, utilities may shift away from coal, lowering the rate. The 2021 to 2022 period saw significant volatility in energy markets, which affected generation patterns across many states.

Seasonal factors also matter. A state with a very wet year will generate more hydroelectric power and lower its annual average. A state with a very dry year will generate less. The eGRID annual rate captures these real-world variations.

Where to find the 2021 and 2022 state rates

The EPA publishes eGRID data on its official eGRID website. You can read the full dataset or view state-by-state summaries. The 2021 data was released in early 2023, and the 2022 data was released in early 2024. Both years are now publicly available.

The EPA website allows you to search by state and see the CO2 rate alongside other information, such as the percentage of electricity generated from each fuel type (coal, natural gas, nuclear, wind, solar, hydroelectric, and other sources). This context helps explain why a state's rate is high or low.

If you need the data in a spreadsheet or database format, the EPA provides downloadable files. These are useful if you are doing calculations across multiple states or years, or if you want to track how a single state's rate has changed over time.

How to use these numbers for your own calculations

If you want to estimate the CO2 emissions from your own electricity use, multiply your annual electricity consumption (in megawatt-hours) by your state's eGRID CO2 rate. For example, if you used 10 megawatt-hours of electricity in a year and your state's rate was 500 lbs/MWh, your electricity use produced roughly 5,000 pounds of CO2.

Most residential electricity bills are measured in kilowatt-hours, not megawatt-hours. One megawatt-hour equals 1,000 kilowatt-hours. So if your bill shows 10,000 kilowatt-hours used in a year, that is 10 megawatt-hours. Multiply by the state rate to get your emissions.

Keep in mind that this calculation assumes you consumed electricity from the average grid mix in your state. If your utility offers renewable energy options or you have rooftop solar, your actual emissions may be lower. The eGRID rate is useful for understanding the baseline carbon intensity of your grid, not for accounting for individual choices you may have made.

Comparing states and understanding what the numbers mean

States with rates below 400 lbs/MWh typically have significant nuclear, hydroelectric, or wind capacity. States with rates above 800 lbs/MWh typically rely heavily on coal. Most states fall somewhere in between, with a mix of natural gas, coal, and renewables.

A state's rate does not tell you whether that state is "good" or "bad" at managing its grid — it reflects geography, history, and available resources. A state with abundant hydroelectric power will naturally have a lower rate. A state with coal reserves and older coal plants will naturally have a higher rate. Over time, rates can shift as states retire old plants and build new ones.

If you are comparing your state to others, the eGRID data gives you a factual basis for that comparison. If you are tracking your own state's progress over time, the year-to-year changes in the eGRID rate show whether the grid is becoming cleaner or dirtier.

Frequently Asked Questions

What is the difference between eGRID CO2 rates and my utility's carbon intensity?

eGRID publishes the average for the entire state. Your utility may publish its own carbon intensity, which reflects only the power plants it owns or contracts with. If your utility uses cleaner sources than the state average, its rate will be lower. If it uses dirtier sources, its rate will be higher. Check your utility's website or annual report for its specific number.

Why do some states have much lower CO2 rates than others?

States with abundant hydroelectric power (like Washington and Oregon), significant nuclear capacity (like Illinois), or large wind farms (like Iowa and Texas) have lower rates. States that rely heavily on coal (like Wyoming and West Virginia) have higher rates. Geography and historical investment in power plants drive these differences.

Can I use the 2021 or 2022 rate to estimate my current emissions?

The most recent eGRID data available is the best choice, but rates do not change dramatically year to year unless a major plant opens or closes. If 2022 is the latest available, using that rate for a 2024 estimate is reasonable. Check the EPA website to see if newer data has been released.

Does my rooftop solar reduce my emissions based on the eGRID rate?

Yes. When you generate your own solar electricity, you avoid drawing from the grid, so you avoid the CO2 emissions associated with that grid electricity. The eGRID rate for your state tells you how much CO2 you avoided per kilowatt-hour generated. If your state's rate is 600 lbs/MWh and you generate 5,000 kilowatt-hours per year, you avoided roughly 3,000 pounds of CO2.

Where can I find historical eGRID data before 2021?

The EPA publishes eGRID reports going back to 2000. Older reports are archived on the eGRID website. If you want to see how your state's CO2 rate has changed over decades, you can read multiple years and compare them.