--- title: How is the Annual Degradation calculated? description: When building the module in our system, we will use the module’s spec sheet to determine the degradation. Most spec sheets will have a performance graph that displays the estimated performance of the --- [Skip to content](https://help.gosolo.io/how-is-the-annual-degradation-calculated#main-content) [![Solo Black-1](https://help.gosolo.io/hubfs/Solo%20Black-1.svg)](https://help.gosolo.io/?hsLang=en) - [Solo Help Center](https://help.gosolo.io/) Open main navigation Close main navigation - [Solo Help Center](https://help.gosolo.io/) - [Go to Solo](https://phx.gosolo.io/) [Go to Solo](https://phx.gosolo.io/) How can we help? - There are no suggestions because the search field is empty. 1. [Solo Help Center](https://help.gosolo.io/?hsLang=en) 2. [Proposals](https://help.gosolo.io/proposals?hsLang=en) 3. [Understanding the Proposal](https://help.gosolo.io/proposals?hsLang=en#understanding-the-proposal) October 31, 2025 # How is the Annual Degradation calculated? When building the module in our system, we will use the module’s spec sheet to determine the degradation. Most spec sheets will have a performance graph that displays the estimated performance of the module over the warranty period (which is typically 25 years). We will pull the efficiency at the end of year 1, the end of the warranty period, and any milestone years provided, then calculate the average decrease in efficiency per year.  That number wll then be used in our production calculations and displayed on the Itemized Details page of the proposal: ![](https://help.gosolo.io/hubfs/Knowledge%20Base%20Import/AD_4nXfzGzXmBIFIe4r59pgiT3pk863A1p4uVziiVRDsBkhgv_ItZAZ5LRjDelBbrvV1ubHaVLxf6Y3k7nXxomJTduhIFFmbU4IvDuCMG6vsbHZMQoKFq50aiRPvHXSekoN4XEH-jhPjVgP-rSDIHj.png) - [Getting Started with Solo](https://help.gosolo.io/getting-started-with-solo?hsLang=en) - [Users & Permissions](https://help.gosolo.io/users-permissions?hsLang=en#main-content) - [Your Account](https://help.gosolo.io/users-permissions?hsLang=en#your-account) - [Managing Users](https://help.gosolo.io/users-permissions?hsLang=en#managing-users) - [User Permissions](https://help.gosolo.io/users-permissions?hsLang=en#user-permissions) - [Customer Management](https://help.gosolo.io/customer-management?hsLang=en) - 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