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Manufacturers' warranty specifications are commonly used as a reference for estimating the degradation of photovoltaic systems, which typically amounts to approximately 20% reduction in relative power after 25 years. Some premium manufacturers now provide warranties for up to 30 years, and efforts are underway to push for 50-year warranties. However, long-term degradation rate data are limited, especially given that over 85% of currently deployed modules have seen less than a decade of use. This issue is even more pronounced in Nordic European climates, where the PV market only started gaining traction in recent years. In this study, we evaluate the performance of a 3.2 kW PV system installed on a rooftop in Sweden in 1994. This system comprises 72 monocrystalline silicon PV modules, each with a capacity of 45 W, and has undergone multiple interventions over the years, including upgrades to power electronics and system configurations. In 2016 and 2024 the modules were tested, revealing a similar average degradation rate of 0.5%/year. Visual inspections were carried out, and apart from light yellowing, no other visible defects such as cracks in the solar cells, delamination, bubbles, hot spots, or rust in connection boxes were observed. © 2024 IEEE.