In most municipalities, local councillors only get small monetary incentives. Since the salary is not high enough to cover the cost of living, the political office is usually only carried out as a part-time job. So far, we do know little about how much time municipal councillors invest in their political activity. Neither do we know on which factors the time investment depends on. This contribution is filling this gap by answering the research question: Which factors explain the time a councillor spends for council-related business? The survey data conducted in 28 European countries is analysed using linear regression analysis. Results show that the time a councillor spends for council-related business depends on various causes on the individual as well as institutional level. Surprisingly, most expectations regarding the influence of individual demographic characteristics proved to be wrong and individual weekly working hours of councillors are not increasing but decreasing if their municipality has a higher LAI score.