Understanding field failure and degradation modes in solar photovoltaic (PV) modules is important for various actors along the value chain. This paper presents results from field studies on performance degradation in twenty-two mono-crystalline silicon modules exposed for 16 years in three communities in the northern part of Ghana, prior to electricity grid extension. The results show, that, maximum power of the modules (P-max) had declined by 18.2-38.8% (median - 24.6%) over the period, which translates to an annual linear degradation rate of 1.54%. The losses in module power output are dominated by losses in short-circuit current (I-sc) and fill factor (FF), which are 0.75%/year and 0.54%/year respectively (median values). Discolouration of the encapsulant and degradation of the junction-box adhesive were the most frequently occurring visually observable defects on the modules.