Calculate how much energy daylight harvesting photosensors will save by automatically dimming lights when natural daylight is available. Savings vary significantly by orientation and climate.
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Daylight harvesting uses a photosensor to measure how much daylight is entering a space and dims the electric lights to make up only the difference. When the room is bright, the lights dim, and when clouds come or evening falls, they brighten. This saves energy in spaces with large windows or skylights without making the room feel dim.
The savings depend on the amount of glazing, the orientation of the windows, the hours the building is used, and the size of the zone near the windows that gets enough daylight. As a rule of thumb, the daylit zone extends back from a window about one to two times the height of the top of the window. The calculator estimates the savings from the fixture power, the hours, the energy price, and the share of time that daylight is sufficient.
To work well, the system must be set up correctly. Place the sensor where it sees the same light as the work area, use dimmable drivers, and calibrate the controls after installation. Blinds and glare can interfere, and some energy codes require daylight controls in certain spaces.