1. HID Lamp – the light source. Also referred to as a grow light or bulb.

2. Ballast – an electrical device that supplies power to the HID lamps. The ballast takes the available voltage from your electrical outlet and ramps it up to provide a high-voltage pulse to start the lamp. It then regulates the voltage to maintain a precise electrical arc inside the lamp. If there are variations in line voltage supplied from your outlet, the ballast adjusts to help maintain the arc. 

There are two types of ballasts: magnetic/core & coil or electronic/digital. Magnetic ballasts, also referred to as core & coil ballasts, use a large spool of wire wrapped around a set of steel sheets to generate the high voltage and wattage required by HID lamps. Electronic ballasts use semiconductors and microchips to provide the high voltage and wattage required by HID lamps. Digital ballasts are electronic ballasts that add smart controls to the inner workings of the ballast to monitor the lamp in various ways.

Not all HID grow lamps will run on both ballast types. Refer to the lamp manufacturer’s operating specifications when choosing a ballast. 

3. Reflector – the device used to reflect the light emitted from an HID lamp. Typically reflectors are made from metal, such as aluminum, and are pressed, hammered or polished to a desired surface finish, impacting its ability to reflect light. Different metals will reflect the light at different values. And those materials will reflect the light at variable values within their family of metal. For example, aluminum has a higher reflectance value than that of steel. Inside the aluminum family, there are varying degrees of reflectivity. It can be made to reflect 95% of light, 97% of light or some other amount. It is the metal manufacturers that control the metal’s ability to reflect light based on the elements used to make up the material. 

The shape and size of a reflector will also affect how well it distributes the light. Common shapes for HID grow lighting include rectangular, parabolic and wing (“bat wing”). Be sure to choose a reflector that will optimize the light coming from your grow lamp based on the lamp’s size and your light distribution goals.