Energy-Efficient, Long-life High Intensity Discharge (HID) lamps / light bulbs, produce light by creating and sustaining an electrical discharge between two electrodes, exciting a mixture of xenon gas and mercury for a bright white light. There are three main types of HID lamps: mercury vapor, metal halide, and sodium. The names reflect the different elements that are used to produce different colors, characteristics, and efficiency.

Mercury Vapor Lamps, the oldest HID technology, gives off a bluish-green light. Advancements have been made to improve the color tint. However, the market is turning more toward better performing metal halide and sodium lamps.

Metal Halide lamps are easily manipulated to give off a light which allows for normal color appearance, which make them ideal for nighttime sports games, photography, and aquarium lighting.

Sodium Lamps are highly energy efficient, but their orange-ish colored light makes surrounding monochromatic. Modern sodium lamps sacrifice some efficiency for improved, whiter light.

On the up side, HID lamps are ideal for large areas where high intensity light and energy savings are important, including gymnasiums, parking lots, football stadiums, warehouses, public areas, and landscaping. Lately, HID has been expanding into the small retail and home markets. On average the lamps last for 15,000 to 24,000 plus hours of use.

On the down side, HID lamps require the use of a ballast to generate light and a somewhat inconvenient warm-up time. The lamps also produce ultraviolet radiation, requiring filters to prevent injury, fading of surrounding dyed areas, and degradation of fixtures.