High Intensity Discharge Lamps are a type of electrical gas-discharge lamp - creating light by passing a current through a gas – much like a fluorescent light. However, as the name implies, High-Intensity Discharge lamps are much brighter and produce a much higher lumen than fluorescents, best used in areas where bright light is needed, such as warehouses, car headlights, streetlamps, stadiums and factories. 

How do They Work?

HID Lamp technology works by filling an arc tube with gas, which also contains a metal or metal salt such as argon or mercury, and running an electric arc through between two tungsten electrodes. This arc heats the metal salts within and produces an intense light.

This process of heating the metal salts can take several minutes and is the reason HID lights can take several minutes to reach full lumen output after being turned on. 

HIDs are more efficient than both halogen and incandescent lighting.  

This family of lights has three main subtypes – the Metal Halide, the High-Pressure Sodium Light, and Mercury Vapour Lamps.

Metal Halide

Metal halide lamps, also called MH Lamps, are known for producing high Lumen with a high CRI. While this reduces it's efficiency slightly, it's still one of the favorites of the HID family. These lamps come with a slightly higher price tag compared to the other lamps. 

Ceramic MH 

Crematic Metal Halide are a newer type of Metal Halide and are 10 – 20 % more efficient than common quartz metal technology. This makes then equal with HPS lamps in longevity. So, although their starting price is higher than other HID lamps on the market, CMH will save you more in the long run. 

Additionally, CMH has the highest CRI of any HID lamp, coming out to 90-92 CRI, making them ideal for areas where strong colour rendering is required. 

High-Pressure Sodium Lights

High-Pressure Sodium Lights (HPS) are another light in the high-intensity discharge (HID) family, along with Mercury Vapour and Metal Halide lamps. HPS lamps have a very low CRI, but a very high lumen per wattage. HPS are best used in places where colour quality is not important - and are commonly used for indoor gardening, as well as warehouse and streetlamp lighting. The produce a warm yellow/orange colour. 

Mercury Vapour Lamps

Mercury Vapour Lamps are the oldest in the HID family, and as the name suggests, use vaporized mercury to produce light. These lamps have a high lux output and are cheap to install and buy compared to Metal Halide and High-Pressure Sodium lamps. In the past, they were commonly used for street lights and high-bay lighting. However, these days they are slowly being phased out, and in Australia, Mercury Vapour Lamps may not meet the lumen requirements for warehouse spaces. They have a greenish tinge to their light.