Independent variables for mid-term forecasting methods: We identify the relevant factors for the DSOs to forecast the electricity infeed in their networks, and quantify their effects. We show that most of the calendar variables, such as national holidays, bridge days and days near holidays have a significant effect on electricity infeed. Our analysis reveals that the impact of calendar variables significantly depends on the hour of the day. On the other hand, economic and demographic factors do not seem to influence the electricity infeed for the planning horizon of DSOs. We also explore the influence of meteorological factors on the electricity infeed in the Netherlands.