Illinois · Retail Power Marketer
Interstate Gas Supply, Inc.
12.73¢ per kWh, energy only, EIA-861 2025. Average bill $78.03 at 612.9 kWh a month, across 22,865 customers on that row.
Illinois averaged 17.67¢/kWh and $126.59 a month. The United States averaged 17.23¢/kWh and $150.68. State and national figures come from EIA's Average Bill file.
Revenue divided by sales, EIA-861 Sales to Ultimate Customers, 2025, released October 7, 2026. Texas wires utilities come from the Delivery Companies file. The price and bill use energy only service. Customer count: 22,865, the largest residential count across service types.
Estimate a bill
The figure below is this utility's 2025 EIA residential average.
2025 EIA average
$127.30
12.73¢/kWh × 1,000 kWh. Energy only residential average, EIA-861 2025. The customer charge is already folded into this average, so it stands beside a tariff total rather than being added to it.
Annual history
| Year | ¢/kWh | Avg. bill | Avg. kWh | Customers |
|---|---|---|---|---|
| 2015 | — | — | — | — |
| 2016 | 8.26¢ | $58.71 | 710.8 | 49,349 |
| 2017 | 8.49¢ | $56.99 | 671.0 | 37,659 |
| 2018 | 9.62¢ | $68.60 | 713.0 | 30,606 |
| 2019 | 10.04¢ | $66.85 | 665.8 | 25,864 |
| 2020 | 9.86¢ | $66.93 | 678.6 | 23,596 |
| 2021 | 10.25¢ | $69.29 | 676.2 | 22,147 |
| 2022 | 12.46¢ | $80.63 | 647.3 | 20,189 |
| 2023 | 11.83¢ | $71.28 | 602.4 | 18,458 |
| 2024 | 11.38¢ | $67.87 | 596.3 | 21,808 |
| 2025 | 12.73¢ | $78.03 | 612.9 | 22,865 |
EIA-861, 2015–2025, using the same service type as the 2025 figure. A blank year means that service was not in the file.
Counties
EIA's 2025 service-territory file does not list counties for this utility.
EIA-861 Service Territory, 2025. A listed county is the county EIA recorded. It does not mean every address in the county is served. Open this utility in the bill calculator · Rate history tool