The numbers that end the debate
Metal halide and high-pressure sodium fixtures are still installed in millions of commercial and industrial spaces. The technology works. It produces light. But it produces that light at 2-3x the wattage, with 50% lumen loss by mid-life, 15-20 minute warm-up times, and maintenance cycles that put electricians on lifts every 18-24 months. The question is not whether LED is better. The question is how much money you are leaving on the table every month you wait. This article gives you the numbers to answer that question for any specific facility.
Wattage equivalents: the replacement table
The most common question on every HID-to-LED conversion: "What LED wattage replaces my existing fixture?" Here is the reference table, with system wattage (including ballast losses for HID) and typical lumen output.
| Metal halide / HPS | System watts (incl. ballast) | Initial lumens (lamp) | LED replacement | LED watts | LED lumens (fixture) | Wattage reduction |
|---|---|---|---|---|---|---|
| 100W MH | ~128W | 8,500 lm | 40-50W LED | 45W | 6,500-7,500 lm | 65% |
| 175W MH | ~210W | 14,000 lm | 60-80W LED | 70W | 10,000-12,000 lm | 67% |
| 250W MH | ~295W | 20,500 lm | 100-120W LED | 110W | 16,000-18,000 lm | 63% |
| 400W MH | ~455W | 36,000 lm | 150W LED | 150W | 22,000-25,000 lm | 67% |
| 1000W MH | ~1,080W | 110,000 lm | 300-400W LED | 350W | 50,000-55,000 lm | 68% |
| 150W HPS | ~185W | 16,000 lm | 60-80W LED | 70W | 10,000-12,000 lm | 62% |
| 250W HPS | ~295W | 27,500 lm | 100-120W LED | 110W | 16,000-18,000 lm | 63% |
| 400W HPS | ~460W | 50,000 lm | 150-200W LED | 175W | 25,000-30,000 lm | 62% |
System wattage includes ballast losses (typically 10-15% above lamp wattage for MH, 15% for HPS). LED lumen values are luminaire lumens (complete fixture output). MH/HPS values are initial lamp lumens (before depreciation and reflector losses). Actual LED replacement wattage should be verified with a photometric layout for the specific mounting height and foot-candle target.
Why fewer LED lumens deliver equal or better light. Metal halide and HPS are omnidirectional: they emit light in every direction, including up into the fixture housing. A reflector redirects the upward light back down, but each bounce loses 15-30% of those lumens. A 400W MH rated at 36,000 initial lamp lumens may only deliver 18,000-25,000 usable lumens to the work surface. LED fixtures are directional: nearly all lumens go straight to the target. A 150W LED at 22,000 fixture lumens delivers most of them to the floor. Fewer total lumens, more usable light.
The five performance gaps that cost you money every month
| Performance factor | Metal halide / HPS | LED | What it costs you |
|---|---|---|---|
| System efficacy | 60-80 lm/W (lamp), 40-50 lm/W effective (after reflector losses) | 130-190 lm/W (fixture, directional) | 2-3x higher electricity cost per delivered foot-candle for HID. |
| Lumen depreciation | Loses 30-50% of lumens by mid-life (10,000 hrs). Still draws full wattage at half brightness. | Maintains 70%+ lumens at 50,000-100,000 hrs (L70 rating). | HID spaces get progressively dimmer while the electric bill stays the same. Or you re-lamp early, which costs more. |
| Warm-up and restrike | 15-20 minutes to reach full brightness. 5-15 minute restrike delay after power interruption. | Instant on/off. No restrike delay. | HID cannot be used with occupancy sensors (you cannot wait 15 minutes for light). This eliminates the single highest-saving control strategy. |
| Maintenance cycle | Re-lamp every 2-3 years (at 4,000 hrs/yr). Replace ballasts every 5-8 years. Each re-lamp requires a lift, an electrician, and a lamp. Multiply by every fixture in the building. | No re-lamping for 12+ years at typical operating hours. No ballast. LED driver failure rate is significantly lower than HID ballast failure rate. | Labor + equipment + lamp cost per re-lamp cycle. For a 50-fixture warehouse, a single re-lamp event costs $2,500-5,000 in labor and materials. |
| Controls compatibility | Cannot dim without expensive magnetic/electronic ballast upgrade. Cannot use occupancy sensors (warm-up time). Cannot integrate with NLC. | 0-10V dimming standard. Instant on/off works with occupancy sensors. Compatible with NLC, DALI, scheduling, daylight harvesting. | HID facilities cannot qualify for NLC rebates, cannot meet ASHRAE 90.1 occupancy/scheduling requirements without replacing the light source first, and cannot implement the control strategies that save 24-38% of lighting energy. |
Worked example: 50-fixture warehouse retrofit
The project
Given: A 50,000 sq ft warehouse with 50 metal halide high bay fixtures. Each fixture: 400W MH lamp + ballast = 455W system draw. Operating 4,000 hours per year. Electricity rate: $0.11/kWh. Fixtures are 8 years old, re-lamped once already.
Annual kWh: 22.75 kW x 4,000 hrs = 91,000 kWh
Annual energy cost: 91,000 x $0.11 = $10,010/year
Maintenance: Re-lamp every 2.5 years (10,000 hrs effective life)
Cost per re-lamp cycle: 50 lamps x $25 + 50 hrs labor x $75/hr = $5,000
Annualized maintenance: $5,000 / 2.5 = $2,000/year
Total annual cost: $10,010 + $2,000 = $12,010/year
LED replacement: 150W high bay fixtures
Annual kWh: 7.5 kW x 4,000 hrs = 30,000 kWh
Annual energy cost: 30,000 x $0.11 = $3,300/year
Maintenance: No re-lamping for 12+ years at 4,000 hrs/yr (50,000 hr L70)
Annualized maintenance: ~$0/year for the first 12 years
Total annual cost: $3,300/year
Savings and payback
Project cost: 50 fixtures x $350 avg (fixture + installation) = $17,500
Rebate: 50 fixtures x $100 prescriptive rebate = $5,000
NLC incentive (if controls added): 50 x $30 = $1,500
Net project cost: $17,500 - $5,000 - $1,500 = $11,000
Simple payback: $11,000 / $8,710 = 1.3 years
5-year net savings: ($8,710 x 5) - $11,000 = $32,550
10-year net savings: ($8,710 x 10) - $11,000 = $76,100
Values are estimates for illustration. Actual fixture, labor, and rebate costs vary by region. Rebate eligibility requires DLC-listed fixtures. For the correct lumen method to verify the LED provides adequate foot-candles, see the lumens guide. For warehouse-specific layout guidance, see the warehouse high bay guide.
The code trigger and rebate opportunity most retrofits miss
Two things happen simultaneously on an HID-to-LED conversion that many contractors do not connect:
The code trigger. If the total wattage being altered exceeds 2,000W, ASHRAE 90.1-2022 Section 9.1.1.3 requires the project to comply with LPD limits AND mandatory controls. Just 5 metal halide fixtures at 455W each (2,275W) exceeds the trigger. The LED fixtures easily meet the wattage reduction, but the controls requirement (occupancy sensors, scheduling) must be in the scope. See the energy code guide for details.
The rebate opportunity. The same controls that the code requires are the same controls that qualify for NLC rebate bonuses ($30-50 per fixture in many utility programs). Adding occupancy sensors and scheduling to meet code simultaneously qualifies for the NLC incentive. The controls are not an added cost; they are scope that was already required by code, and they come with their own rebate. See the rebate guide for program details.
Where each application-specific guide picks up
This article covers the universal HID-to-LED comparison. For application-specific layout guidance, fixture selection, and worked examples:
| Application | Guide |
|---|---|
| Warehouse / distribution center | Warehouse High Bay Lighting Guide (ceiling height, beam angles, spacing, UFO vs. linear) |
| Parking lot / area lighting | Parking Lot Lighting Guide (pole heights, Type III vs V, dark sky compliance) |
| Gas station / petroleum canopy | Gas Station Canopy Guide (NEC 514 hazardous zones, canopy foot-candles) |
| Fluorescent troffer replacement | Fluorescent to LED Retrofit Guide (Type A vs B vs retrofit kit) |
| Dimming and controls | Dimming Protocols Guide (0-10V, DALI, wireless NLC) |
| Energy code compliance | ASHRAE 90.1 Energy Code Guide (LPD limits, controls requirements) |
Frequently asked questions
What LED wattage replaces a 400W metal halide?
150W LED. The metal halide system draws approximately 455W including ballast, so the LED provides a 67% wattage reduction. The LED delivers comparable or better usable light because it is directional (no reflector losses), while the metal halide is omnidirectional and loses 15-30% of its lumens to reflector bounce. Verify with a photometric layout for the specific application.
How much does switching from metal halide to LED save?
A typical 400W MH fixture costs $200-250/year to operate at 4,000 hours. The 150W LED costs $66-75/year. Energy savings: $130-185 per fixture per year. Add maintenance savings (no re-lamping, no ballast replacement) and total savings per fixture is $180-250/year. For a 50-fixture warehouse, that is $9,000-12,500 annually. Payback after rebates: typically 1-3 years.
Why do fewer LED lumens produce equal or better light?
Metal halide is omnidirectional: it throws light in all directions, including up into the fixture housing. Reflectors redirect some of that light downward, but each bounce loses 15-30%. A 400W MH at 36,000 initial lamp lumens may only deliver 18,000-25,000 usable lumens to the floor. LED is directional: nearly all lumens go straight down. A 150W LED at 22,000 fixture lumens delivers most of those to the work surface.
How long do metal halide lamps actually last?
Rated life is 15,000-20,000 hours, but effective life is much shorter. By 10,000 hours, most MH lamps have lost 30-50% of initial lumens while still drawing full wattage. Many facilities re-lamp at 10,000-12,000 hours to maintain adequate light levels. LED fixtures maintain 70%+ lumens at 50,000-100,000 hours (L70), which is 5-10x the effective metal halide lifespan.
Does the retrofit trigger energy code compliance?
If the total wattage being altered exceeds 2,000W, yes. Just 5 metal halide fixtures at 455W each exceeds the trigger (2,275W). The LED retrofit easily meets the 50% wattage reduction path, but the mandatory controls requirement (occupancy sensors, scheduling) often adds scope. See the energy code guide.
Can I put an LED lamp in an existing metal halide fixture?
LED retrofit lamps exist for mogul base (E39) sockets, but this is the weakest conversion path. The optics are not optimized (the lamp sits inside a housing designed for omnidirectional light), the old ballast may draw parasitic power or be incompatible, and most retrofit lamps are not DLC listed (no rebate eligibility). A complete fixture replacement or retrofit kit delivers better optics, higher efficacy, and DLC listing. For the comparison of retrofit methods, see the fluorescent-to-LED retrofit guide (the same decision framework applies to HID).
