Sizing LED UFO High Bays: Technical Guide, ROI & Compliance – Hyperlite

Upgrading a facility from legacy metal halide (MH) or high-pressure sodium (HPS) systems to LED is no longer just about reducing the electric bill—it is a strategic overhaul of operational safety and visual performance. The most common mistake facility managers make is attempting a 1:1 wattage replacement. In the LED era, wattage is a measure of power consumption, not light output.

To achieve professional results, you must shift your focus to delivered lumens and photometric uniformity. A 400W metal halide fixture does not require a 400W LED; in fact, a high-efficacy 200W to 240W LED high bay typically delivers superior illumination due to higher Luminous Efficacy (measured in lumens per watt, or lm/W).

This guide provides the technical framework to size your UFO high bays correctly, grounded in industry standards and real-world performance data.

The Lumen vs. Wattage Paradigm Shift

In traditional lighting, we relied on wattage as a proxy for brightness. However, a 400W MH lamp typically starts at 36,000 lumens but loses 30% to 50% of its output halfway through its life. Furthermore, MH lamps are omnidirectional, meaning much of their light is lost or trapped within the fixture housing.

Modern LED UFO high bays are inherently directional. According to the IES LM-79-19 Standard (Optical/Electrical Measurement), which defines the approved method for measuring solid-state lighting, LED performance is verified based on the "absolute" photometry of the entire fixture, not just the light source. This means the lumen rating on a quality LED spec sheet represents the actual light exiting the fixture.

When evaluating efficacy, look for products that meet or exceed the DesignLights Consortium (DLC) Premium requirements. DLC Premium-certified fixtures often exceed 140 lm/W, whereas standard MH systems struggle to maintain 60–80 lm/W after initial burn-in.

Sizing Your High Bay: The Technical Framework

Selecting the right brightness depends primarily on two factors: Mounting Height and Application Type. Industrial spaces require different "foot-candles" (fc)—a measure of light intensity on a surface—depending on whether the task involves bulk storage or precision assembly.

The following table serves as a pragmatic baseline for sizing UFO high bays in typical industrial environments.

Mounting Height	Recommended Lumens	Typical LED Wattage	Spacing (Center-to-Center)	Target Application
10 – 15 ft	10,000 – 15,000 lm	80W – 100W	10 – 15 ft	Small Garages, Low-level Storage
15 – 20 ft	18,000 – 22,000 lm	150W	15 – 20 ft	Workshops, Retail, Gymnasiums
20 – 30 ft	26,000 – 30,000 lm	200W – 240W	20 – 25 ft	Manufacturing, Large Warehouses
30 – 40 ft	36,000+ lm	300W – 400W	25 – 30 ft	High-ceiling Distribution Centers

Note: For ceilings above 30 ft, while a standard 120° beam angle works, you may consider 90° optics to push more light vertically toward the floor, though 120° is often sufficient if spacing is tight enough.

High-ceiling industrial warehouse and assembly floor with evenly spaced LED high bay fixtures providing bright, uniform illumination

Photometrics and the Spacing Rule of Thumb

A common pattern we observe in poorly lit warehouses is the "checkerboard effect"—bright spots directly under fixtures and dark shadows in between. This is a failure of Uniformity.

Experienced contractors apply the Mounting Height = Spacing Distance rule of thumb. If your lights are mounted at 20 feet, they should generally be spaced 20 feet apart. This ensures the 120° beam patterns overlap sufficiently at the work plane (usually 0 to 3 feet above the floor).

The 10-15% Lumen Buffer

In industrial environments, dust and airborne particulates accumulate on the fixture lens over time. This is known as the Luminaire Dirt Depreciation (LDD) factor. To maintain the required light levels over a five-year period, experts recommend adding a 10% to 15% lumen buffer to your initial calculations. If your layout requires 20,000 lumens to meet code, specify a fixture capable of 22,000 to 23,000 lumens.

Verifying with IES Files

Before purchasing, always request the .ies file (photometric data file) for the specific SKU. This file allows engineers to run an AGi32 Lighting Software simulation. This simulation provides a "point-by-point" calculation of the light levels across your entire floor plan, ensuring your uniformity ratio stays between 0.7 and 1.0.

Compliance, Safety, and ROI Analysis

Upgrading to LED is a capital investment, and maximizing Return on Investment (ROI) requires leveraging utility rebates and meeting building codes.

Safety Standards

Ensure any fixture you select is UL 1598 listed. This standard covers luminaires for use in non-hazardous locations and is the first point of verification for electrical inspectors and insurance providers.

Energy Codes and Controls

Modern codes like ASHRAE Standard 90.1-2022 and California Title 24 now mandate more than just high efficiency. They often require:

Occupancy Sensing: Lights must dim or turn off when the area is vacant.
Daylight Harvesting: Fixtures near windows or skylights must dim automatically when natural light is present.
0-10V Dimming: This is the industry standard for commercial LED control.

Worker installing LED High Bay lights in a high-ceiling industrial workshop from a scissor lift

Scenario Analysis: The 40-Foot Warehouse Simulation

To demonstrate the impact of proper sizing, we simulated a 120' × 80' (9,600 sq. ft.) bulk-storage warehouse with a 40-foot mounting height.

Scenario A: Legacy System (Baseline)

Fixtures: 5 x 458W Metal Halide
Total Power: 2,290 Watts
Performance: High maintenance, rapid lumen depreciation, poor color quality.

Scenario B: Optimized LED Retrofit

Fixtures: 5 x 360W High-Efficacy LED UFOs (36,000 lm each)
Total Power: 1,800 Watts
Beam Angle: 120°
Results:
- Annual Energy Savings: ~$3,449.60
- Maintenance Savings: ~$780.00 (avoided relamping labor/materials)
- HVAC Impact: ~$14.15 (reduced cooling load from lower lighting heat)
- Simple Payback: 0.68 Years (approx. 8 months)

In this high-ceiling scenario, the primary challenge was uniformity. Using only five high-output fixtures saved on installation labor while the 120° beam angle provided broad enough coverage to eliminate dark spots between the 30-foot spacing intervals.

LED High Bay lights illuminating a high-ceiling industrial warehouse; tablet shows photometric beam patterns for aisle and open-floor layouts.

Installation Gotchas and Pattern Recognition

After auditing hundreds of retrofits, several "non-obvious" mechanical issues consistently emerge:

Voltage Mismatch: While most commercial buildings use 120-277V, many heavy industrial sites operate on 347V or 480V systems. Installing a standard 120-277V driver on a 480V circuit will cause immediate failure. Always verify the supply voltage before ordering.
Dimming Wire Interference: When running 0-10V dimming wires, avoid running them in the same conduit as high-voltage power lines unless the dimming wires are rated for it (Class 1 vs. Class 2 wiring). Interference can cause flickering or "ghosting" where lights won't fully turn off.
The "Visual Parallax" Error: Facility managers often set mounting heights based on the bottom of the trusses. However, if you use a pendant mount, the light source might sit 2-3 feet lower. This reduces the effective beam spread on the floor, potentially requiring more fixtures to maintain uniformity.
IP and IK Ratings: For wash-down areas or food processing, an IP65 rating (dust-tight and water-jet protected) is mandatory. In gyms or areas with forklift activity, look for an IK08 or IK10 rating, which measures resistance to mechanical impact.

Selecting the Right Color Temperature (CCT)

Color temperature significantly affects worker productivity and safety. According to the ANSI C78.377-2017 Standard, CCT should be consistent across a facility to prevent eye strain.

4000K (Neutral White): Preferred for manufacturing and spaces where workers spend 8+ hours. It provides high clarity with less "blue light" fatigue.
5000K (Daylight White): The standard for warehouses, high-ceiling storage, and shipping bays. It mimics daylight, keeping workers alert and making labels easier to read.

LED High Bay and LED shop lights showing 4000K, 5000K, 6000K in barn, garage, and warehouse

Maximizing Long-Term Reliability

Don't be misled by "100,000-hour" marketing claims without data. Reliable manufacturers provide IES LM-80 reports (measuring chip lumen maintenance) and TM-21 projections (mathematically predicting lifetime). A high-quality fixture should maintain at least 90% of its light output (L90) for at least 50,000 hours.

By prioritizing these technical artifacts—LM-79 reports, IES files, and DLC Premium certification—you move from "guessing" your lighting needs to "engineering" a high-performance environment that pays for itself in months, not years.

YMYL Disclaimer: This article provides technical information for educational purposes only. Electrical installations involve significant risks, including fire and electrocution. All lighting retrofits and electrical work should be performed by a licensed electrician in accordance with the National Electrical Code (NEC) and local building regulations.