What are the degradation rates for solar panels?

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Although highly durable, solar panels will degrade in efficiency over time. This means that a 30 year old panel will not produce as much electricity as it did when it was brand new. It is important to take this factor into consideration in order for you to determine if your system is producing at the rate that it should. This is especially important if you want to hold your solar installer accountable for promises made when they sold you your system.

Solar panels typically come with 20 year warranties that guarantee that the panels will produce at least 80% of the rated power after 20 years of use. The rate at which the panels degrade depends on the brand and model of panel. Each manufacturer provides estimates for degradation rates, which are typically highest in the first year and then lower for subsequent years. For example, the LG335N1C-A5 panel is projected to degrade by 2% in the first year, and 0.5% for each subsequent year. By contrast, the LG335N1C-V5 panel is projected to lose 2% in its first year, but only 0.33% in each subsequent year. Over the course of a couple of decades, these differences can be significant.

SolarView takes this degradation into consideration as it provides you with ongoing reports of system performance. The Settings page allows you to configure the monthly production estimates, as provided to you by your solar installer, and the degradation rates for the panels, as provided by the panel manufacturer:

Once this information has been entered into the SolarView settings, the system will keep track of your production month over month, and year over year, so you will know if the system is producing energy at the rates guaranteed in your installation contract. If the system is falling short of your installer’s contractual guarantees you will have the data that you need to explore remedies.

SolarView gives you access to this data in two ways. Each month, SolarView will email and/or text a production report to you that will also include an estimate of production surplus or deficit based on the estimates and degradation rates that you entered in Settings. In addition, the Reports menu in the SolarView desktop monitor will allow you to browse results by year. In the example below, the report reveals that the system has been producing a surplus of energy, compared to the estimates provided by the solar installer, since going online in October, 2019.