by Sarah Nuss-Warren, President-Elect
UUFoM installed solar panels in 2024, with the first energy credits available for June. Since installation, we have generated almost 12,000 kWh and earned over $1225 in credits toward our Consumers Energy bill. Estimated, this is about 78% of our electricity usage since the panels were installed, not including energy delivered as natural gas and primarily used for heating. An estimate is provided rather than an exact figure because the bill from December 2024 was not available. To determine the estimate, UUFoM substituted the use and generation from December 2025 for December 2024. This is a great success in reducing the amount of energy we use from non-renewable sources and in offsetting ongoing costs!

As expected, our solar panels generate more energy from May through September, when Michigan has lower cloud cover and the northern hemisphere tilts toward the sun. In the summer, we typically generate more electricity than we use. In October through April, we typically use more than we generate or come close to breaking even.

The energy generated decreased by anywhere from 10% to 30% in a month-to-month comparison between 2024 and 2025. It is too early to know how much of this is from the normal aging of the panels and how much from differences in weather, such as cloud cover; debris, such as pollen; or shading from trees. Some decrease in efficiency with time is normal for solar panels. According to the National Renewable Energy Laboratory’s 2012 preprint about degradation of photovoltaic cells (Jordan & Kurtz), the median degradation among almost 2000 solar panels studied was 0.5% per year, and the average was 0.8% per year. In other words, half of the solar panels degraded by 0.5% or less per year, but a few degraded by as much as 4% per year, heavily influencing the average. Based on our July-to-July decrease of 10%, once the weather begins to warm, we may want to examine possible external causes for the measured decrease, such as excessive shading or dust on the solar panels. Such investigation may reveal maintenance options to further enhance the effectiveness of our investment.
Jordan, D. C., & Kurtz, S. R. (2013). Photovoltaic Degradation Rates—An Analytical Review. Progress in Photovoltaics: Research and Applications, 21(1), 12-29. Preprint. https://docs.nrel.gov/docs/fy12osti/51664.pdf