To raise awareness on the importance of monitoring photovoltaic (PV) systems in the Netherlands, a public campaign was organised in three consecutive years. During 1 week in the spring of 2014, 2015, and 2016, as part of the Dutch Solar Days, participants were asked to measure or determine the amount of energy generated by their PV systems. All in all over 8000 participants were recruited via social media and a national television show. This study analyses the variation of weekly yield and performance ratio (PR) of the systems of the participants for 3 years. On average, for each year, a PR was found of 0.74 with a left-skewed distribution, indicating that most systems perform well. Further analysis was made, which showed the ineffectiveness of an undersized inverter in low radiation conditions. It was also found that the performance difference between mono- and multicrystalline silicon panels was small, and that micro-inverters are effective in reaching high performance for PV systems that suffer from shading. Generally, this work demonstrated the usefulness of citizen science approaches in PV system performance analysis.