Daylighting only saves energy if it temporarily replaces electric lighting. As a consequence, energy savings due to daylight depend not only on the annual daylight available at a work place but also on when and how occupants use their blinds and lighting controls.
A unique features of DAYSIM is a manual lighting control model, called "Lightswitch". The model combines annual illuminance profiles and user occupancy with behavioral patterns that are based on field studies in office buildings throughout the Western world. For example, the model predicts when users will lower window blinds in response to glare, or when they will switch on the electric lighting.