This FAQ has been posted to the Illinois Shines FAQ page.
Question: Does my system produce electricity in winter months?
Answer: Yes, solar systems still produce electricity in the winter months, but production could be significantly lower due to winter’s shorter days, the lower angle of the sun in winter, and snowfall that may occasionally cover your panels.
If your solar system was designed to offset all of your annual electricity usage, it was likely designed to produce excess electricity in summer months, which can balance out lower production experienced in winter months. Under the Illinois Public Utilities Act (Sec. 5/16-107.5. Net electricity metering), utilities must allow unused net metering credits (from high production months during spring and summer) to carry forward and offset subsequent electricity usage until the end of your annual period (which you can choose to be either the end of April or October each year).
After the annual period closes, these credits expire and can no longer be used toward your electricity bill. If you install solar in the fall or winter, your system has not yet had a chance to generate excess credits during high production months. This could result in your electricity bill not decreasing significantly since the installation occurred during lower production months. At this point in the year when lower production occurs, your system’s production might be simply meeting the needs of your home/property thus not generating any excess power just yet.
Please note that if you are not a customer of ComEd, Ameren, or MidAmerican, excess net metering credits may or may not carry forward. Additionally, keep in mind that the carrying forward of net metering credits only applies to specific rate classes, which can vary depending on utility. Please check with your electric utility to learn more about its specific metering policy.
If you believe that your system is underperforming, please contact your Installer for more information. If you have questions about your Illinois Shines application, please contact your approved vendor.