Definition
High bay and low bay LED fixtures serve the same purpose (downward area illumination from ceiling) but at different mounting heights. High bays are designed for ceilings above 20ft (6m): they use higher wattage (100-500W), higher lumen output (15,000-60,000 lm), and narrower optics (60-90° beam) to project light down from height while minimizing waste on walls. Low bays are designed for ceilings 8-20ft (2.5-6m): lower wattage (40-200W), lower lumen output (5,000-25,000 lm), and wider optics (90-120° beam) for broader distribution at closer range. Using a high bay at low ceiling height causes harsh glare and hot spots. Using a low bay at high ceiling height results in dim, uneven illumination.
Key Data
| Parameter | Value / Explanation |
|---|---|
| Mounting height | High bay: >20ft (6m+), Low bay: 8-20ft (2.5-6m) |
| Typical wattage | High bay: 100-500W, Low bay: 40-200W |
| Lumen output | High bay: 15,000-60,000 lm, Low bay: 5,000-25,000 lm |
| Beam angle | High bay: 60-90° (narrower for height), Low bay: 90-120° (wider for proximity) |
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Application Guide
Warehouse (30ft ceiling)
UFO high bay, 200W, 28,000 lm, 90° beam
Designed for this height — uniform illumination at floor level
Workshop (14ft ceiling)
Low bay linear, 100W, 14,000 lm, 120° beam
Wide distribution needed at close range; high bay would create harsh glare
Conclusion & Procurement Recommendation
The mounting height determines the fixture type, not preference. Measure from floor to luminaire mounting point. ≥20ft = high bay. <20ft = low bay. For mixed-height facilities: use both types, separated by zone. The wrong choice is immediately obvious on installation — don't guess, calculate.