This article presents the degradation rates over eight years for 3000 PV installations distributed across the UK. The study considers three PV cell technologies, namely, monocrystalline silicon (Mono-Si), polycrystalline silicon (Poly-Si), and thin-film Cadmium Telluride (CdTe). The available raw data undergoes three key stages: normalization, filtering, and aggregation, before the degradation analysis of the considered installations. This algorithm can be considered as one of the paper contributions. Results show that a maximum degradation rate of -1.43%/year is observed for the CdTe type, whereas Poly-Si and Mono-Si PVs have annual degradation rates of -0.94% and -0.81% respectively. Moreover, this article exploits the monthly mean performance ratio (PR) for all the examined PV sites. The highest PR value of 87.97% is calculated for the Mono-Si PV installations, while 85.08% and 83.55% is calculated for Poly-Si and CdTe installations, respectively.