Coal-fired ownership represents nearly 70% of our Naperville/IMEA power supply, such that the greenhouse gas (GHG) emissions from this coal-fired ownership represents the major climate change risk from our power supply. IMEA tells us, in the IMEA Fiscal Year 2021 annual report, that 45% of our power supply comes from the 15.17% IMEA ownership share of the Prairie State Energy Campus (PSEC) and another 23% of our power supply comes from the 12.12% IMEA ownership share of the two Trimble County KY coal-fired generators.

Since there are no current plans by Naperville or IMEA to transition this coal-fired ownership, our total Naperville/IMEA GHG emissions rate cannot fall below the weighted contribution of these coal-fired ownership emissions.  Although Naperville and IMEA do not report GHG emissions or emissions rates, we have used the U.S. EPA’s eGRID data to calculate the weighted Naperville/IMEA coal-fired ownership emissions rate in CO2-equivalents (CO2e).  CO2e emissions represent the sum of emissions for three GHGs: CO2 (carbon dioxide), CH4 (methane), and N2O (nitrous oxide), each multiplied by a global warming potential (GWP) factor for each gas.

The weighted Naperville/IMEA coal-fired ownership emissions rate is approximately 1,500 pounds of CO2e per megawatt hour (1,500 CO2e lbs/MWh). Furthermore, this weighted Naperville/IMEA coal-fired ownership emissions rate is:

Almost double the emissions rate of our ComEd neighbors (795 CO2e lbs/MWh)

More than two and a half times the emissions rate for Illinois (556 CO2e lbs/MWh)

We should expect that the above Naperville/IMEA comparison ratios with ComEd and Illinois will grow even larger, as the other coal-fired generation plants in Illinois continue to close between now and 2030. The ComEd and Illinois emissions rates should continue to decrease, while our Naperville/IMEA emissions rate cannot fall below that “floor level” of 1,500 CO2e lbs/MWh.

No matter how much clean energy comprises the remaining 30% of the Naperville/IMEA power supply, we have that “floor level” of 1,500 CO2e lbs/MWh until Naperville/IMEA address our coal-fired ownership.

We can also expect that the actual Naperville/IMEA emissions rate will remain much higher than 1,500 CO2e lbs/MWh, depending on the fossil fuel energy mix of that remaining 30%. The Naperville Environment and Sustainability Task Force (NEST) reported a total emission rate of 1,992 CO2e lbs/MWh, which is 492 above our the 1500 “floor level” primarily due to the emissions of IMEA’s coal-fired power purchase contract with Vistra, a contract which ended in May 2022.

This webpage information is also available as a pdf file document “Greenhouse Gas Emissions from Naperville/IMEA Coal-Fired Ownership” which also contains further notes on PSEC, Trimble County, eGRID, CO2e, GWP, and the details of our calculations and comparisons.