Significant changes to Illinois' net metering policies took effect on January 1, 2025. These changes substantially impact new solar customers who install their systems after this date. The Arcadia team previously created experimental tariffs to empower users to gain familiarity with these new tariffs and test calculations before these changes go into effect; we have now finalized production tariffs. Additionally, Arcadia conducted a detailed analysis to assess how these changes might affect solar savings.

Who is Impacted

The 2025 net metering changes in Illinois primarily impact investor-owned utilities, such as ComEd, Ameren, and Mid American. These utilities are regulated by the Illinois Commerce Commission and will be required to comply with the new regulations. However, electric cooperatives and municipal utilities, which are not classified as public utilities under Section 3-1191, may not be subject to these changes. This means that while the majority of large providers will need to implement the new rules, some smaller cooperatives and municipally-owned utilities might have exemptions
Interpretation of Changes
The 2025 changes in Illinois restructure net metering credits as part of a transition to a value-based compensation framework for solar energy. This approach, similar to New York’s Value of Distributed Energy Resources (VDER), focuses on optimizing grid and demand management rather than solely incentivizing solar growth.

• Reduced Net Metering Benefits: New solar customers will see a reduction in net metering benefits, with credits limited to the supply portion of their bill. Existing customers will continue to receive full benefits.
• Real-Time Resolution: Based on the language in the available documents, Arcadia believes that imports and exports will be resolved in real-time, rather than at the billing period level. Exact behavior is subject to publication of final documents by Illinois PUC and the respective utilities.
• Billing Structures: Two billing structures will be available:
  • Non-bypassable delivery and service charges delivery
  • Credits from net metering can reduce and service charges only if there are remaining credits after minimizing supply charges. Ameren's residential customers will primarily face non-bypassable charges.
    These changes are expected to result in a net decrease in the avoided cost of power for Illinois utilities.

2025 Illinois Net Metering MTIDs

The aforementioned experimental tariffs are now the default tariffs, with 'Experimental' and 'EXP' removed from their names and codes, respectively. For net-metered tariffs, the tariff names (before 2025) will have '- Net Metered' appended, and the tariff codes will include '-NEM.' Note: In some cases, experimental tariffs had names slightly different from the originals; in those cases, the new default will align with the original name before appending '- Net Metered' or '-NEM' to indicate net-metered status.

When running a Savings Analysis, Arcadia assigns a default post-solar tariff for each LSE. The default post-solar tariffs are now:

• ComEd: 3479678
• Ameren: 3479265
• MidAmerican: 3483534

Avoided Cost of Power (ACP) Analysis

• Substantial Reduction in Savings: Our analysis shows that these changes significantly reduce the avoided cost of power for solar customers. For ComEd customers on the four primary residential tariffs, the avoided cost of power is expected to drop by an average of nearly 40%. Similarly, Ameren and MidAmerican customers will see a reduction of just over 32% and 28%, respectively. This means that the financial benefits of solar will be significantly diminished for new customers in Illinois post-2025.
• Impact on Net Metering Credits: Previously, Illinois provided a 1:1 credit for each kilowatt-hour (kWh) of electricity sent back to the grid, covering the entire electric bill. Starting in 2025, new solar customers will only receive credits for the supply portion of their bill, effectively cutting the net metering credit in half.
• Grandfathering for Existing Customers: Customers who installed solar panels and were approved for net metering before December 31, 2024, will be grandfathered into the current rates. This ensures they continue to receive the full net metering benefits for the life of their system, typically up to 30 years.

Data & Calculator Updates

There are no data or other changes required to use these new MTIDs in your workflows. However, users need to understand the interconnection dates of the project in question. For interconnection dates before January 1, 2025, use the pre-2025 tariffs. All pre-2025 tariffs remain active, but are no longer the default. For interconnection dates on January 1, 2025 or later, use the post-2025 tariffs.

Please reach out to our Support team at [email protected] or directly via your Account Manager or Customer Support Representative, where applicable.

Best regards,
Arcadia Platform Support Team