A ballast is an electrical device that provides the starting voltage for fluorescent and high-intensity discharge (HID) lamps and then limits the current flowing through them.
Without one, these lamps would draw ever more current and fail. For decades, garages and parking lots were lit by metal halide, high-pressure sodium and fluorescent lamps, all of which need ballasts. Most new parking lighting is LED, which uses an electronic driver instead.
Types
- Magnetic ballasts, older, heavier and less efficient, sometimes with an audible hum.
- Electronic ballasts, lighter and more efficient, operating lamps at high frequency without flicker.
- HID ballasts for metal halide and high-pressure sodium lamps, which also need warm-up and restrike time.
Why it matters in a retrofit
- Ballasts consume energy themselves and fail over time, adding maintenance.
- HID lamps cannot be switched or dimmed easily, which rules out most energy-saving controls.
- Replacing ballast-based fixtures with LED usually cuts energy use substantially and allows adaptive controls.
- Old magnetic ballasts may contain PCBs and need proper disposal.
The Parkonomics view
If a garage still runs on ballasts, its lighting is due for replacement. LED with controls typically pays back quickly in a facility lit around the clock.
Related terms: Ballast Factor, LED Lighting, Metal Halide Lighting, Adaptive Lighting, Lighting Power Density, Return on Investment