Decoding Floodlight Specifications: A Practical Guide to NEMA Beam Spreads
Selecting the right LED floodlight for a commercial property involves more than just picking the brightest option. The true measure of performance lies in precision—how effectively a fixture directs light onto a target area without creating hazardous glare or wasteful light spill. An incorrect beam spread can undermine a security plan, leaving critical zones in shadow while spilling light onto adjacent properties.
This technical guide demystifies the National Electrical Manufacturers Association (NEMA) beam spread classification system. Understanding this industry standard is the key to moving beyond vague terms like "narrow" or "wide" and specifying the exact floodlight beam pattern your application requires, whether you're illuminating a building facade, a parking area, or a security perimeter.
What Exactly Is a NEMA Beam Spread?
The NEMA beam classification is a two-number system that defines the horizontal and vertical distribution of a floodlight's beam. Before this standard, specifiers were left with inconsistent marketing terms. The NEMA Lighting Systems Division created this system to provide a uniform, reliable language for describing a luminaire's photometric performance.
The "beam angle" or "spread" is the angular dimension of the cone of light where the intensity is at least 50% of its maximum candlepower. A NEMA classification, such as 6x7, provides this information in two dimensions.
- The first number (H) represents the horizontal beam angle.
- The second number (V) represents the vertical beam angle.
Each number corresponds to a specific angular range, as detailed in the table below (based on published NEMA standards).
| NEMA Type | Beam Angle (degrees) |
|---|---|
| 1 | 10° to < 18° |
| 2 | 18° to < 29° |
| 3 | 29° to < 46° |
| 4 | 46° to < 70° |
| 5 | 70° to < 100° |
| 6 | 100° to < 135° |
| 7 | 135° and wider |
Note: For definitive technical specifications, always refer to the latest official NEMA documentation.
A fixture with a NEMA 6x7 classification, for example, has a horizontal beam spread between 100° and 135° and a vertical beam spread of 135° or more. This tells you immediately that it produces a very wide, circular or oval-shaped pattern of light.
Selecting the Right NEMA Beam Spread for Your Application
Choosing the correct beam spread is a function of two variables: the fixture's mounting height and the shape of the target area. Getting this right is crucial for achieving uniform illumination and maximizing the fixture's effectiveness.
Match Beam Angle to Mounting Height
A common mistake I see in the field is using a beam spread that is too wide for the mounting height. This creates a dim, ineffective pool of light and significant glare. A sound heuristic, based on years of layout designs, is to match the beam angle to the pole or building height.
- High Mounting (≥25-30 ft): Use narrow beams (NEMA 1, 2, or 3). The tight angle concentrates light, ensuring it reaches the ground with sufficient intensity from a great height. This is ideal for high-mast lighting in large lots or sports fields.
- Medium Mounting (15-25 ft): Medium beams (NEMA 4 or 5) are the workhorses for most general-purpose site lighting, including parking lots and building perimeters. They offer a good balance of intensity and coverage area.
- Low Mounting (<15 ft): Wide beams (NEMA 6 or 7) are best for low mounting heights or for applications like wall-washing, where the goal is to cast a broad, diffuse layer of light across a wide surface.
Fixtures like the versatile Hyperlite Led Flood Light - Mars Series are designed to be effective in these scenarios, provided the correct NEMA spread is chosen for the specific mounting height and aiming angle.
Match Beam Shape to the Target Area
The H x V classification allows you to match the light pattern to the geometry of the ground or facade you need to illuminate.
- Tall Building Facades: To light up the width of a building without wasting light into the sky, an asymmetric beam like a NEMA 7x4 is effective. The wide horizontal spread (Type 7) covers the building’s width, while the tighter vertical spread (Type 4) controls the upward projection.
- Long Perimeters or Driveways: To push light down a long, narrow path, a NEMA 3x7 or similar would be appropriate. The narrow horizontal beam minimizes spill to the sides, while the wide vertical beam throws light forward and backward along the path.
- Square Lots or Open Areas: For general area lighting, a symmetrical beam like a NEMA 6x6 or 7x7 provides a roughly circular pattern that can be overlapped to create uniform coverage. This is the typical pattern for fixtures like the Hyperlite LED Parking Lot Light - Zeus Series, which are designed to efficiently illuminate large, open spaces.
Case Study: Simulating a Parking Lot Perimeter
To illustrate the impact of NEMA selection, let's consider a real-world scenario: illuminating a 200-foot-long section of a security fence from a single pole mounted at 20 feet.
Objective: Achieve consistent illumination along the fence line for security camera visibility.
- Incorrect Choice: NEMA 7x7 (Wide, Symmetrical): A common mistake would be to use a generic "wide" floodlight. A 7x7 beam would create a large circular pattern. While it might light up the area directly under the pole, it would waste over 50% of its light into the parking lot and sky, leaving the ends of the fence line dangerously dark. The illuminance would drop from 3.0 foot-candles near the pole to less than 0.2 foot-candles at the ends.
- Correct Choice: NEMA 3x7 (Narrow Horizontal, Wide Vertical): A specialized asymmetric beam is the professional solution. The narrow NEMA 3 horizontal spread contains the light within the immediate perimeter zone, preventing spill. The wide NEMA 7 vertical spread throws the light far down the 200-foot fence line.
Simulation Results: A photometric simulation using the IES file for a NEMA 3x7 fixture confirms the superior performance. It produces a long, rectangular pattern of light that aligns perfectly with the fence.
The simulation shows an average of 1.5 foot-candles across the entire length, with a uniformity ratio (max:min) of 3:1—ideal for clear video surveillance. This is a prime example of how choosing the right NEMA type achieves better security with less wasted energy.
Pro Tip: Ask your lighting provider for a sample IES file for your chosen fixture. You can use free IES viewers or professional software to verify the distribution pattern before purchasing.
Common Mistakes and Expert Heuristics
Beyond the basics, experienced specifiers use a deeper level of analysis to avoid common pitfalls and ensure a lighting plan is both effective and efficient.
Myth Debunked: "More Lumens is Always Better"
A prevalent misconception is that the floodlight with the highest lumen output is the best choice. In reality, uncontrolled lumens are a liability. A 30,000-lumen floodlight with a NEMA 7x7 beam aimed carelessly will produce more disabling glare and light trespass than a 15,000-lumen fixture with a precisely aimed NEMA 4x5 beam. The goal of security lighting is visibility. Glare bombs reduce visibility for cameras and security personnel. An effective lighting plan prioritizes controlled, uniform illumination over raw power.
The Specifier's Pitfall: Ignoring Photometric Files
One of the most frequent mistakes is specifying a fixture based on its marketing name—like "wide flood"—instead of verifying its performance. The only source of truth for a luminaire's performance is its photometric data file, commonly known as an IES file. This standardized format, defined in detail by the Illuminating Engineering Society's IES LM-63-19, ensures that photometric data is reliable and transferable between different software platforms. The file contains a complete, authoritative map of the fixture's light distribution.
My advice is simple: always request the .ies file. Lighting design software like AGi32 uses these files to simulate exactly how a light will perform in a real-world environment, showing foot-candle levels, uniformity ratios, and potential glare. Without this step, you are guessing.
Quick Field Estimations
Before running a full photometric layout, you can use a quick heuristic to estimate a beam's coverage on the ground. For a circular beam aimed straight down, the diameter of the coverage area is approximately:
Coverage Diameter ≈ 2 × Mounting Height × tan(Beam Angle / 2)
For a 40-foot pole with a fixture that has a 60° NEMA 5 beam, the calculation would be 2 × 40 × tan(30°), which yields a coverage diameter of about 46 feet. This simple formula is a great way to sanity-check if a proposed fixture is even in the right ballpark for the application before you invest time in a detailed design.
Your NEMA Selection Checklist
Use this step-by-step checklist to guide your decision-making process. For a convenient on-site reference, you can download a PDF version of this checklist.
Step 1: Determine Mounting Height
- High (>25 ft / 8m): Start with narrow beams (NEMA 1, 2, 3) to project light effectively to the ground.
- Medium (15-25 ft / 5-8m): Start with medium beams (NEMA 4, 5) for general area and site lighting.
- Low (<15 ft / 5m): Start with wide beams (NEMA 6, 7) for wall washing or broad coverage at close range.
Step 2: Define Target Area Geometry
- Square or Circular Area? Use a symmetrical beam (e.g., 4x4, 5x5, 6x6).
- Long, Narrow Area (e.g., roadway, perimeter)? Use an asymmetrical beam with a wider vertical angle (e.g., 3x7, 4x6).
- Tall, Wide Area (e.g., building facade)? Use an asymmetrical beam with a wider horizontal angle (e.g., 7x4, 6x5).
Step 3: Verify with Photometrics
- [ ] Does the manufacturer's spec sheet clearly state the NEMA HxV classification?
- [ ] Have you requested the official IES photometric file for the exact model?
- [ ] Have you or a lighting designer simulated the IES file in software to confirm foot-candle levels and uniformity for your specific site geometry?
Wrapping Up: Key Takeaways for Precise Floodlighting
To move from amateur to professional-grade lighting specification, focus on control and precision. Use these principles as your guide:
- Trust the Numbers: Use the NEMA H x V classification to understand the precise shape of the light beam. Do not rely on generic marketing terms.
- Consider the Geometry: Match the beam spread to the mounting height and the shape of your target area. Use narrow beams for height and asymmetrical beams for long or tall targets.
- Verify with Photometrics: Never finalize a specification without first reviewing the IES file. This is the only way to guarantee performance and avoid costly installation mistakes.
- Prioritize Control Over Power: Effective and responsible lighting is about placing the right amount of light exactly where it is needed. A well-aimed, properly specified floodlight will always outperform a brighter, poorly chosen one.
Important Safety and Compliance Disclaimer
The information in this guide is for general informational purposes. Lighting design for security and public safety is a critical task that carries significant responsibility. For any installation impacting public access, traffic safety, or high-security zones, you must consult a qualified lighting designer or a licensed professional engineer to ensure safety and compliance.
All electrical installations must be performed by a licensed electrician and must strictly adhere to all applicable local, state, and national electrical codes, building codes, and municipal ordinances regarding light levels, glare, and light trespass.
Frequently Asked Questions (FAQ)
What's the difference between a NEMA beam spread and an IES distribution type (e.g., Type III)? NEMA beam spread (e.g., 6x7) describes the shape and angle of the light cone itself—how focused or wide it is. IES distribution types (e.g., Type I, II, III, IV, V) describe how the light is thrown forward and sideways from the fixture, primarily for roadway and parking lot applications. They are complementary specifications; a Type III fixture will also have a NEMA beam spread.
Can I use a floodlight with a wide NEMA spread on a tall pole? While you can, it is highly inefficient. A wide beam (like NEMA 6 or 7) from a 30-foot pole will spread the light over such a large area that the intensity on the ground (measured in foot-candles) will be very low. It's much more effective to use a narrower beam (NEMA 2, 3, or 4) to concentrate the light where it is needed.
Where can I find the NEMA beam spread for a light fixture? The NEMA classification should always be listed on the manufacturer's official specification sheet (often called a "spec sheet" or "cut sheet"). It can also be found within the IES photometric file for the luminaire.