The degradation rate measures how much the performance of a solar panel decreases each year. According to the National Renewable Energy Laboratory (NREL), solar panels typically lose 0.5% of their efficiency annually. Initially, they operate at 99% capacity, after the first year they drop to 98.05% and over 25 years, their efficiency falls to around 84-85%.
REC batteries degrade more slowly, maintaining 92% efficiency after 25 years, which qualifies them as premium batteries.