High-intensity-discharge (HID) light sources, such as metal halide and high-pressure sodium lamps, have long dominated the market for lighting indoor spaces with high ceilings. These “high-bay” spaces are typically found in warehouses, factories, large retail stores, and athletic facilities. In recent years, however, improvements in fluorescent lighting technology have resulted in the emergence of new high-output fluorescent fixtures, which are superior to HID fixtures in numerous ways.

Combining T8 & T5 fluorescent tubes with electronic ballasts and highly efficient reflective fixtures, high-output fluorescent systems are considerably more efficient than comparable HID systems. Furthermore, they feature lower lumen depreciation rates, better dimming options, virtually instant start-up and restrike, and better color rendition. These additional benefits are so compelling that designers may specify high-output fluorescent systems even if they saved no energy at all.

Additional cost savings are possible in refrigerated or climate controlled facilities because cooling loads are significantly reduced. Fluorescent fixtures and lamps generate much less heat than HIDs, which means that climate control equipment does not have to run as hard or as long to maintain correct temperature and humidity indoors. In some cases, businesses have been able to avoid costly heating, ventilation, and air conditioning upgrades by retrofitting their lighting system instead.

HID manufacturers are improving their products as well. For example, new lamp and ballast designs make HIDs more efficient and faster starting. New reflector designs are making HID fixtures much more efficient as well. However, until HID manufacturers make dramatic improvements in energy requirements, start-up times and lumen depreciation rates, high-output fluorescents will continue to be advantageous in a variety of applications.