UFO High Bay Wattage Chart by Area & Height
If you want a fast, reliable way to size UFO high bay lights, start with lumens and area—not watts or marketing “HID equivalents.” This guide provides ready‑to‑use wattage charts by square footage and mounting height, plus a repeatable calculation method used by lighting professionals.
Based on the Illuminating Engineering Society (IES) RP‑7‑21 standards for industrial facilities, typical warehouses require 20–30 foot-candles (fc) for bulk storage and 30–50 fc for active picking or packing. The charts below translate these targets into recommended lumens and UFO high bay wattage based on realistic efficacy and maintenance factors.
Expert Resource: Downloadable Design Tools
To help you move from "rule of thumb" to a verified layout, we have provided the following technical assets:
- [Example IES Files (.ies)]: Standard 150W UFO photometric data for use in AGi32 or Dialux.
- [Sample LM-79 Test Report (PDF)]: A mock report showing how to verify actual lumen output and efficacy.
- [UFO Lighting Calculator (Excel)]: An editable sheet with built-in formulas for Total Lumens, Fixture Count, and LPD (Lighting Power Density).
1. Key Design Assumptions Behind the Wattage Chart
In our experience supporting warehouse retrofits, the most common mistake is ignoring the difference between "catalog lumens" and "delivered lumens" over time. Every value in the charts below is built on these three professional assumptions.
1.1 Maintenance Factor (MF): Designing for Year 5, Not Day 1
We assume a Maintenance Factor (MF) of 0.75. This accounts for:
- Lumen Depreciation (LLD): Based on TM‑21 projections, LEDs lose 5–10% of output over the first few years.
- Luminaire Dirt Depreciation (LDD): In typical industrial environments (Level 2 or 3 dirtiness), dust on the UFO lens can reduce output by 10–15%.
Pro Tip: If you design to exactly 30 fc with "New" lumens, your facility will likely drop to 22 fc within three years. We always recommend sizing for 1.25x the target to ensure long-term compliance.
1.2 Efficacy: The 140–160 lm/W Benchmark
Wattage is a measure of power consumption, not brightness. Following the DOE FEMP guidance, high-performance UFOs should achieve at least 140 lm/W.
- 150W (Standard): ~18,000–21,000 lumens.
- 150W (High-Efficacy): ~24,000+ lumens. Our charts assume a mid-range efficacy of 150 lm/W. If your chosen fixture is lower (e.g., 120 lm/W), you must increase the wattage by approximately 20% to achieve the same result.
1.3 Reflectance and Environment
These calculations assume "medium" reflectance: 50% Ceiling / 30% Walls / 20% Floor. If you have a black "open deck" ceiling or dark racking, the light levels will be 15–20% lower than the chart suggests.
2. Quick UFO High Bay Wattage Chart by Area & Height
This chart provides a starting point for open warehouses, gyms, or large garages.
| Area (ft²) | Mounting Height (ft) | Typical Application | Target Avg fc (Maintained) | Total Lumens (Catalog) | # of Fixtures (Suggested) | Suggested Wattage/Fixture |
|---|---|---|---|---|---|---|
| 400–600 | 10–12 | Small Garage/Shop | 30 fc | 24,000 | 2–4 | 40–60 W |
| 1,200–2,000 | 12–15 | Auto Bay/Workshop | 35 fc | 75,000 | 4–6 | 80–100 W |
| 3,000–5,000 | 16–20 | Medium Warehouse | 25 fc | 150,000 | 8–12 | 100–120 W |
| 5,000–10,000 | 20–25 | Logistics Center | 25 fc | 300,000 | 12–18 | 150 W |
| 15,000+ | 25–35 | Large Distribution | 25 fc | 500,000+ | 20+ | 200–240 W |
Case Study: 10,000 ft² Warehouse Retrofit
- Before: (24) 400W Metal Halide fixtures (approx. 10,800W total). Measured 18 fc (uneven).
- After: (18) 150W UFO High Bays (2,700W total). Measured 32 fc (uniform).
- Result: 75% energy reduction with a 77% increase in light levels. The client qualified for a $2,700 utility rebate ($150/fixture) because the units were DLC Premium listed.
3. The 7-Step Sizing Method
Use this repeatable process to verify any project.
- Calculate Area: Length × Width.
- Determine Target FC: (e.g., 30 fc for general work).
- Find "Maintained Lumens": Area × Target FC.
- Find "Catalog Lumens": Maintained Lumens ÷ 0.75 (Maintenance Factor).
- Select Fixture Wattage: Based on the efficacy (e.g., 150 lm/W).
- Check Spacing (SMHR): Ensure fixtures are spaced no further than 1.5× the mounting height apart to avoid "cave effect" dark spots.
- Calculate LPD: Total Watts ÷ Total Area. Compare this to ASHRAE 90.1-2022 Table 9.6.1, which typically limits warehouses to 0.41–0.45 W/ft².
4. Height-Based Wattage Guardrails
A common mistake at low mounting heights (≤14 ft) is using a single 200W fixture to cover a large area. This creates intense glare and "hot spots" directly underneath.
| Mounting Height | Recommended Wattage | Best Practice |
|---|---|---|
| 10–14 ft | 60W – 100W | Use more fixtures with wider beam angles (120°) to improve uniformity. |
| 15–20 ft | 100W – 150W | The "sweet spot" for most UFOs. Standard 90° or 120° optics work well. |
| 21–30 ft | 150W – 240W | Consider 90° optics to push light down to the floor and rack faces. |
| 30 ft+ | 240W – 300W+ | Narrow beam (60°) may be required for high-pile storage to maintain vertical fc. |
5. Compliance, Rebates, and Controls
For professional and commercial projects, the wattage choice is often dictated by local energy codes.
5.1 Lighting Power Density (LPD)
Under IECC 2024 (Section C405.3) and California Title 24, you cannot simply "over-light" a space. You must stay under a specific wattage per square foot. If your design exceeds 0.50 W/ft² for a warehouse, you likely need a more efficient fixture (higher lm/W) rather than more watts.
5.2 Mandatory Controls
Most modern codes (ASHRAE 90.1 / Title 24) require:
- Occupancy Sensing: Lights must dim or turn off when the aisle is empty.
- Daylight Harvesting: If you have skylights, fixtures near them must dim automatically.
- 0-10V Dimming: Standard on most UFOs, this allows the "high-end trim" to be set, potentially reducing a 150W fixture to 120W if the space is too bright.
5.3 DLC Listing and ROI
To qualify for North American utility rebates (e.g., ConEd, PG&E, Duke Energy), the fixture must be listed on the DesignLights Consortium (DLC) QPL.
- DLC Standard: Meets basic efficacy.
- DLC Premium: Higher efficacy and better lumen maintenance (L90); often qualifies for 20–50% higher rebate amounts.
6. Common Myths About UFO Wattage
-
Myth: "Higher Kelvin (6000K) means I can use lower wattage."
- Reality: While 6000K looks "brighter" due to blue light content, it does not change the foot-candle reading. High-CCT light can actually increase glare and eye strain in detailed work environments. Stick to 4000K or 5000K for better visual comfort.
-
Myth: "A 150W LED always replaces a 400W Metal Halide."
- Reality: A cheap 150W LED with 110 lm/W only produces 16,500 lumens. A 400W MH (after ballast loss and depreciation) might still be delivering 18,000+ lumens. You must compare delivered lumens, not just watts.
Key Takeaways
- Calculate by Lumens: Target 25–30 fc for storage and 40–50 fc for work areas.
- Use the 0.75 Factor: Always derate your light levels to account for dirt and age.
- Check Height: Lower ceilings need lower-wattage fixtures spaced closer together to prevent glare.
- Verify Efficacy: Aim for >140 lm/W to ensure you are getting the most light for your electricity dollar.
- Consult a Pro: For any project requiring a permit, ensure your LPD and control strategy meet local IECC or Title 24 requirements.
FAQ
Q: How many watts do I need for a 2,500 ft² shop with a 14 ft ceiling?
A: Based on our chart, you need ~75,000 catalog lumens. We recommend (6) 80W or 100W UFOs. This provides excellent uniformity and approximately 30–35 maintained foot-candles.
Q: What is the spacing rule for UFO lights?
A: A good heuristic is a 1:1 ratio. If your lights are mounted at 20 ft, space them roughly 20 ft apart. Do not exceed 1.5:1 (30 ft apart) or you will see dark "valleys" between fixtures.
Q: Does mounting height change the wattage I should buy?
A: Yes. As you move higher, light "spreads" more. To maintain the same foot-candles at 30 ft as you had at 15 ft, you need significantly more lumens (and thus more wattage or tighter spacing).
Safety & Compliance Disclaimer
This guide is for informational purposes. Electrical installations must be performed by a licensed electrician in accordance with the National Electrical Code (NEC) and local building regulations. Energy code compliance (ASHRAE/Title 24) should be verified by a qualified lighting designer or engineer.
Sources & Precise References
- IES RP-7-21: Recommended Practice: Lighting Industrial Facilities. Table 11.1 (Illuminance Targets).
- ASHRAE 90.1-2022: Energy Standard for Sites and Buildings. Table 9.6.1 (LPD Limits).
- ANSI/IES LM-79-19: Approved Method: Optical and Electrical Measurements of Solid-State Lighting.
- ENERGY STAR: LED Technology Fact Sheet (Lumen Maintenance and Thermal Stress).
- DLC Technical Requirements V5.1: Efficacy and Control Requirements.