A warehouse high bay retrofit swaps metal halide, high-pressure sodium or fluorescent high bays for LED fixtures. The new fixtures should be sized to your mounting height, rack layout and tasks. Done well, you hit the light levels IES guidance calls for, gain controls that work with instant-on LEDs, and cut lift-truck relamping. You can estimate payback from a few inputs: watts removed, operating hours, your electric rate and net project cost.
UFO vs. linear high bays
Both styles are LED, and both can be excellent. The difference is how they shape the light.
| UFO (round) high bay | Linear high bay | |
|---|---|---|
| Light pattern | Round, concentrated output | Spread along the fixture’s length; aisle optics are widely available |
| Best fit | Open floors, high ceilings, replacing round HID fixtures one-for-one | Rack aisles, lower mounting heights, replacing T5HO/T8 fluorescent high bays |
| Mounting | Hook, pendant or conduit; small footprint | Chain, cable or surface; longer footprint |
| Watch for | Glare at lower heights without a reflector or lens | Correct alignment with aisles |
Whichever you choose, look for a DesignLights Consortium (DLC) listing. Utility Company Rebate Programs commonly require it, along with other conditions. Browse our high bay fixtures to compare styles.
Choosing lumens by mounting height
These are common starting points per fixture, not rules. Ceiling and floor reflectance, rack height, fixture spacing and the task all change the answer.
| Mounting height | Typical starting range per fixture |
|---|---|
| 15–20 ft | 10,000–18,000 lumens |
| 20–30 ft | 18,000–30,000 lumens |
| 30–40 ft | 30,000–45,000 lumens |
Before you buy, ask for a photometric layout. It shows predicted footcandles on the floor and on rack faces, so you aren’t guessing. Note that some utility rebate programs set a minimum mounting height for high bay measures, so check the program terms.
Beam angles and optics
- Narrow (about 60°): tall ceilings and narrow aisles where you need light pushed down to the floor.
- Medium (about 90°): the general-purpose choice for many open warehouses.
- Wide (about 120°): lower mounting heights and open floor areas where you want broad overlap.
- Aisle or asymmetric optics: throw light onto rack faces so pickers can read labels on upper shelves.
Vertical light on rack faces matters as much as light on the floor. Pickers read labels on the shelf, not on the floor.
How much light? IES recommendations
The current Illuminating Engineering Society reference is ANSI/IES RP-7-21, Lighting Industrial Facilities. It gives recommended minimum maintained light levels and maximum uniformity ratios, adjusted by task. Ranges commonly cited from IES warehouse guidance:
- Inactive storage: about 5–10 footcandles
- Active storage, large items: about 10–20 footcandles
- Active storage, small items or small labels: about 20–50 footcandles
- Uniformity in rack areas: horizontal average-to-minimum no more than 3:1; vertical no more than 10:1
Use these as orientation and confirm targets against the RP-7-21 tables for your tasks. Also check each fixture’s rated ambient temperature. In Georgia summers, the air near the roof deck of an unconditioned warehouse gets far hotter than the floor.
Occupancy and daylight controls
Metal halide needs minutes to warm up and restrike, so it usually stays on all shift. LEDs come on instantly, which makes controls practical.
- Occupancy sensors: high bay-rated sensors, either built into the fixture or networked. In forklift aisles, many facilities dim to a low level instead of switching fully off.
- Daylight sensors: dim fixtures near skylights, clerestories and open dock doors.
- Scheduling: networked systems can set zones by shift and report energy use.
Energy codes often require automatic controls when lighting is replaced or added. Confirm what applies to your project with your electrician or local building official. Some Utility Company Rebate Programs pay extra for on-board occupancy sensors on qualifying high bays. Controls that code already requires usually do not qualify for control rebates.
How to think about payback
Skip the generic payback claims and run your own numbers. You need these inputs:
- Existing watts per fixture. Use system watts, which includes the ballast, not the number printed on the lamp.
- New LED watts per fixture, from the spec sheet.
- Annual operating hours by zone. Count your real shifts and weekends.
- Your cost per kWh from your utility bill, plus any demand charges that a lower connected load may reduce.
- Hours or watts saved by controls.
- Net project cost: fixtures, labor and lifts, minus rebates.
- Maintenance you’ll stop paying for.
Then do the math:
- Annual kWh saved = (old watts − new watts) × number of fixtures × annual hours ÷ 1,000
- Annual energy dollars saved = kWh saved × your rate
- Simple payback in years = net project cost ÷ (annual energy savings + annual maintenance savings)
In conditioned spaces, lower lighting heat can also reduce cooling load. That counts in Georgia’s long cooling season.
Maintenance savings
HID lamps lose output as they age, and relamping or replacing ballasts 30 feet up means renting a lift and blocking aisles. LED fixtures are rated by L70, the hours until output falls to 70 percent of initial. Compare L70 claims that are backed by standardized test data. Ask about driver warranties, too, since the driver is a common failure point. Fewer lift days also means less disruption to picking and loading.
Start with an energy audit
A good retrofit starts with a count. That means fixture types and wattages, hours by zone, measured footcandles and the controls already in place. Our energy audits put that on paper and point to the zones with the fastest payback. They also flag which measures fit Utility Company rebate programs. For broader options, see our warehouse lighting selection.
Frequently asked questions
How many lumens do I need for a 25-foot warehouse ceiling?
A common starting range is about 18,000–30,000 lumens per fixture. The right number depends on spacing, racks and your task, so confirm it with a photometric layout.
Are UFO or linear high bays better for rack aisles?
Linear fixtures with aisle optics usually suit narrow rack aisles because they spread light along the aisle and onto rack faces. UFOs shine in open areas and high ceilings.
Can I retrofit my existing HID high bays instead of replacing them?
Often, yes. LED retrofit kits replace the light source inside the existing housing, and utility rebate catalogs often include kits that replace HID sources. Full replacement is usually better if housings are corroded or optics are poor.
Do warehouse LED upgrades qualify for utility rebates?
Many do. Programs commonly require DLC-listed products, minimum annual operating hours and a real cut in wattage. Program terms and amounts change, so check the current catalog.
Ready to plan a retrofit for your warehouse or distribution center in North Fulton, Forsyth or anywhere in metro Atlanta? Send us your fixture count and ceiling heights through our volume order and quote request, and our lighting design team will help you choose fixtures, optics and controls.
