Degradation analysis of polycrystalline silicon modules from different manufacturers under the same climatic conditions

•Degradation of p-Si modules from different manufacturers under same climatic conditions analysed.•Mean power degradation rates of modules from different manufacturers range from 0.79 to 1.67%/year.•Modules from only one manufacturer degraded less than the warranty rate of 0.8%/year.•Power degradation rate has no correlation with age but the power degradation of all modules was mainly due to Isc degradation.•Discoloration of encapsulant and metallisation, and corrosion of frames found on modules from 4 manufacturers.