During an initial period of time, an HVAC controller receives an indoor humidity and an outdoor humidity. A record of an energy demand of the HVAC system is stored for each indoor humidity and outdoor humidity. For a future time period, an anticipated energy demand of the HVAC system is determined. The controller then recursively determines, for each of a plurality of time points within the future time period, an anticipated indoor humidity value using the anticipated energy demand and the record of the energy demand. The HVAC system is operated based at least in part on the anticipated indoor humidity value.