How to Choose LED Lumen Output When Replacing Metal Halide or HPS
HID retrofits fail most often for one reason: the replacement is sized off lamp watts instead of delivered lumens. Metal halide (MH) and high-pressure sodium (HPS) lamps publish “initial lumens,” but the lumens that reach the pavement or workplane are reduced by ballast factor, lamp depreciation, and luminaire optical losses.
This guide uses two references: (1) published HID lamp initial lumen data (for MH and HPS) and (2) a practical “rule-of-thumb” lumen target for LED replacements by existing HID wattage and mounting height.
Quick Rules Before You Use Any Conversion Chart
- Don’t convert watts to watts. Convert HID system performance to LED luminaire lumens and match the optic/distribution to the layout.
- Use “mean” performance thinking. HID output drops materially over life; LED depreciation is typically slower, so an LED that “looks brighter” on day one can still be the correct choice.
- Account for distribution. A Type III area light on a slip fitter throws forward; a flood on a trunnion is directional. Same lumens, different results.
- Start with the chart, then validate with height + spacing. A conversion chart is a screening tool, not a photometric.
Metal Halide to LED Equivalency Chart
Metal halide lamps often have high initial lumens (lamp data), but many retrofits target a lower LED lumen package because the LED lumens are typically stated as luminaire lumens (after optical losses). Use the “Recommended LED Target Lumens” column as the practical selection range, then confirm the optic for the application.
| Existing Lamp | Typical MH Initial Lumens (Lamp) | Recommended LED Target Lumens (Luminaire) | Typical LED Wattage Range (120–160 lm/W) | Notes (Use Case) |
|---|---|---|---|---|
| 175W Metal Halide | 13,300–15,000 lm | 10,000–15,000 lm | 65–125 W | Low/mid poles, small lots, perimeter zones |
| 250W Metal Halide | 19,000–23,000 lm | 15,000–24,000 lm | 95–200 W | Common parking + site applications |
| 400W Metal Halide | 32,500–40,000 lm | 18,000–30,000 lm | 115–250 W | Higher poles, wider spacing, higher fc targets |
| 1000W Metal Halide | 107,000–115,000 lm | 48,000–72,000+ lm | 300–600 W | Large areas, sports/perimeter, high mounting heights |
Source notes: MH initial lumen values shown are representative lamp data from a major HID lamp manufacturer; LED target lumens align to a commonly used “replacement lumens” rule-of-thumb and may be adjusted up/down based on the site’s foot-candle target, pole spacing, and distribution.
High-Pressure Sodium to LED Equivalency Chart
HPS lamps are efficient at producing amber lumens, but the color and distribution often drive LED conversions for visibility and spill control. Use this chart to pick an LED lumen package, then validate optics (Type III/IV/V) to keep light on the property.
| Existing Lamp | Typical HPS Initial Lumens (Lamp) | Recommended LED Target Lumens (Luminaire) | Typical LED Wattage Range (120–160 lm/W) | Notes (Use Case) |
|---|---|---|---|---|
| 70W HPS | 6,300 lm | 5,000–8,000 lm | 32–67 W | Small perimeter, walkways, compact lots |
| 100W HPS | 8,800–9,500 lm | 8,000–12,000 lm | 50–100 W | Perimeter + small lot poles |
| 150W HPS | 14,000–16,000 lm | 12,000–18,000 lm | 75–150 W | Common parking lot replacement tier |
| 250W HPS | 28,000 lm | 18,000–30,000 lm | 115–250 W | Higher poles / wider spacing |
| 400W HPS | 47,500–51,000 lm | 30,000–48,000 lm | 190–400 W | Large lots / high-output perimeter |
| 600W HPS | 91,500 lm | 48,000–72,000+ lm | 300–600 W | Very high-output areas |
| 1000W HPS | 140,000 lm | 72,000+ lm | 450–800+ W | Rare; validate glare/trespass carefully |
Mounting Height and Spacing Sanity Check
After you pick a lumen package, make sure it matches the mounting height band. A practical height-to-lumen guideline is below (use it as a screening check):
| Typical Mounting Height | Common LED Lumen Packages That Fit | Why It Matters |
|---|---|---|
| 10–20 ft | 8,000; 12,000–15,000 lm | Too many lumens at low height increases glare and spill |
| 20–30 ft | 12,000–15,000; 18,000–30,000 lm | Most parking lots sit here; optic choice drives uniformity |
| 30–40 ft | 18,000–30,000; 36,000–60,000 lm | Higher poles need more lumens, but glare control becomes critical |
| 40–60 ft | 36,000–72,000 lm | Spacing and distribution dominate; don’t “over-lumen” to fix layout |
Common Mistakes That Create Complaints
- Over-lamping with LEDs because the old HID wattage “feels big.” Excess lumens at low height creates glare and neighbor complaints.
- Wrong distribution (ex: Type V where Type III is needed), causing light trespass and dark zones.
- Ignoring pole spacing and trying to “fix” uniformity by tilting the fixture aggressively.
- Comparing to HID on day one without considering HID lumen depreciation and maintenance cycles.
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Frequently Asked Questions
Why do flat panels often cause more screen reflections?
Flat LED panels are Lambertian emitters, meaning they push light out in a very wide, 120-degree arc. This includes high-angle light that travels almost horizontally across the ceiling. When this light hits a computer monitor, it reflects directly into the user's eyes as a veiling reflection. While flat panels are great for uniform floor lighting, their lack of high-angle cutoff makes them high-risk for glare in dense workstation areas.
What makes a Volumetric troffer better for computer work?
Volumetric fixtures use a recessed optical cavity and internal reflectors to shape the light. This design creates a natural cutoff angle, preventing light from traveling at those sharp horizontal angles that cause screen glare. By directing more light downward and less light sideways into people's peripheral vision, volumetric troffers create a quiet ceiling that feels brighter but looks less glary.
Does Edge-Lit vs. Back-Lit matter for glare?
Not significantly. Edge-lit and back-lit refer to where the LEDs are located inside a flat panel, but both typically use a similar diffuse lens that scatters light in all directions. If you are choosing a flat panel specifically for an office, look for a UGR (Unified Glare Rating) < 19. This rating indicates the fixture has a micro-prismatic lens designed to suppress high-angle brightness, mimicking some of the benefits of a volumetric troffer.
Can I use volumetric fixtures in a low-ceiling office?
You can, but you must be careful with spacing. Because volumetric fixtures have a more controlled, narrower throw, they can create hot spots on the floor and shadow bands on the ceiling if they are spaced too far apart in a room with 8-foot or 9-foot ceilings. In low-ceiling environments, Flat Panels with UGR-lowering lenses often provide the best balance of uniformity and glare control.
How does CCT (Color Temperature) impact perceived glare?
While CCT doesn't change the physical angle of the light, it changes how our eyes perceive it. A 5000K (Daylight) flat panel often feels sharper and more glary than a 3500K or 4000K fixture, even if the lumen output is identical. For open offices, 3500K is the 2026 standard for high visual comfort, as it provides a warmer, more paper-like contrast on computer screens compared to cooler blue-white light.
Brandon Waldrop
As the lead technical specialist for our commercial lighting technical operations, Brandon Waldrop brings over 20 years of industry experience in product specification, outside sales, and industrial lighting applications.
His career began in physical lighting showrooms, where he focused on hands-on product performance and technical support. He later transitioned into commercial outside sales, working directly with architects, electrical contractors, and facility managers to translate complex lighting requirements into energy-efficient, code-compliant solutions.
Today, Brandon applies that industry experience to architect high-performance digital catalogs and technical content systems, helping commercial partners streamline the specification process and deploy lighting solutions with total technical confidence.