A method for scheduling cleaning of a photovoltaic (“PV”) system is implemented by a soiling monitoring computer system. The method includes determining a soiling level and a soiling rate for a photovoltaic (PV) system, calculating a cost associated with cleaning the PV system at each of a plurality of possible cleaning times, determining an expected energy output gain associated with cleaning the PV system at each of the plurality of possible times based on the soiling level and the soiling rate, calculating an expected benefit associated with cleaning the PV system at each of the plurality of possible cleaning times based on the expected energy output gain associated with each possible cleaning time, determining a first time of the plurality of possible times when the expected benefit exceeds the cost, and scheduling a cleaning time based on at least the determined first time.