Hps To Led Wattage Conversion

高压钠灯到LED瓦数转换

Let's get one thing straight right off the bat: there's no single "multiply by 0.5" rule that works everywhere. I've seen too many procurement specs that just halve the wattage and call it a day—and then the parking lot ends up looking like a cave. The real conversion depends on what you're lighting and what standard you're chasing.

Recommended Values by Application

Notice the range in those LED wattages. That's not sloppy engineering—it's because a 150W LED high-bay with a 120° beam spread won't give you the same floor illuminance as one with a 60° narrow optic at the same wattage. The luminaire's optical efficiency and the room's cavity ratio matter just as much as the raw lumens.

Specification Comparison

Here's the thing: a "minimum" spec at 100 lm/W with Ra 60 will still beat a 400W HPS lamp that's only pushing 80 lm/W after 12,000 hours of operation. But you'll hate the color quality—everything looks like it's under a sodium streetlight again. Don't cheap out on CRI if you're doing retail or office work.

Why Hps To Led Wattage Conversion Matters

Let's put numbers to this. A typical 400W HPS high-bay in a warehouse draws about 460W from the wall when you include the ballast losses (IEC 60598-1:2020, Annex J). Run that 24/7 at $0.12/kWh, and you're looking at $483 per fixture per year. Replace it with a 150W LED that delivers the same 100 lux maintained on the floor, and that drops to $157. That's a 67% energy reduction—real money when you've got 200 fixtures.

But it's not just about the electricity bill. HPS lamps lose 30–40% of their initial lumens by 24,000 hours (IESNA LM-80-15, Section 4.2). LEDs, properly designed, maintain 90% or more at 50,000 hours. So the conversion ratio you calculate at day one isn't the same as what you'll see three years in. I've walked into warehouses where the HPS system was so degraded the client thought they needed 200 lux, but the actual measured illuminance was 60. A proper conversion starts with a site measurement, not a nameplate.

What does this mean in practice? You can't just swap a 250W HPS streetlight for a 100W LED and assume you're good. The EN 13201-2 luminance requirements for road surfaces are based on maintained values, not initial. If the LED driver is set to 100W but the thermal management is poor, you'll lose 15% output in summer—and suddenly your road doesn't meet the ME4a standard. Always spec the LED luminaire for the maintained performance, not the initial.

Application Scenarios

Warehouse retrofit. You've got 400W HPS high-bays on 12m centers in a 15m ceiling warehouse. The existing system delivers 80 lux average on the floor—below the EN 12464-1 minimum of 100 lux for general warehousing. A 150W LED high-bay with 130 lm/W and a 90° beam will hit 120 lux maintained, with a uniformity ratio (U0) of 0.65. That's above the 0.60 minimum. The catch: you need to check the mounting height. If the LED fixture is heavier than the HPS unit, you might need to reinforce the catwalk. I've seen that stop a project cold.

Street lighting conversion. A 250W HPS cobra-head on a 10m pole with a 15m spacing gives about 0.70 cd/m² average luminance on an asphalt road—just under the EN 13201-2 ME4a requirement of 0.75 cd/m². A 100W LED with a Type II medium distribution and 130 lm/W will hit 0.80 cd/m² maintained, with a longitudinal uniformity (U1) of 0.70. But here's the practical aside: make sure the LED luminaire's photometric distribution matches the road geometry. A Type III distribution on a narrow road will waste light into the yards and annoy the neighbors.

Parking lot. A 150W HPS floodlight on a 8m pole covers about 20m x 20m at 10 lux average. That's the IESNA RP-20-14 minimum for basic parking. A 60W LED floodlight with 130 lm/W and a 120° beam will give you 12 lux average with a uniformity of 0.40—above the 0.33 minimum. But if the parking lot has security cameras, you'll want to bump the CCT to 5000K and the CRI to 70, because HPS's 2200K light makes everything look like a sepia photo. The camera won't see details.

High-bay industrial. A 1000W HPS in a foundry with 20m ceilings delivers 180 lux on the floor. The EN 12464-1 requirement for fine assembly is 500 lux. You're not even close. A 400W LED high-bay with 140 lm/W and a 60° narrow beam will hit 520 lux maintained. But the ambient temperature in that foundry hits 55°C. The LED driver needs to be rated for that—check the IEC 60598-1 thermal test. If the driver's Tc point is 75°C and the ambient is 55°C, you've only got 20°C of headroom. That's tight.

Design Guidelines

Start with the maintained illuminance target from the relevant standard—EN 12464-1 for interiors, EN 13201-2 for roads, IESNA RP-20 for parking. Measure the existing HPS system's actual illuminance with a calibrated lux meter at the task plane. Don't trust the nameplate. HPS lamps degrade, ballasts fail, and optics get dirty.

Use the lumen method for a first-pass calculation: Required LED lumens = (Target lux × Area × Maintenance factor) / (Luminaire coefficient of utilization × Room cavity ratio factor). The maintenance factor for LEDs should be 0.85–0.90 for a clean environment, 0.70–0.80 for dirty industrial (IESNA LM-80-15, Section 5.1). For HPS, the maintenance factor is typically 0.60–0.70 after 12,000 hours. That alone accounts for a 20–30% wattage reduction.

Rule of thumb from the field: for most commercial and industrial applications, the LED wattage will be 35–45% of the HPS wattage when comparing equivalent maintained illuminance. But that's a starting point, not a spec. Always run a photometric simulation in AGi32 or Dialux before ordering. I've seen a 40% conversion ratio work perfectly in a clean warehouse with white walls, and fail completely in a dark foundry with 8m ceilings.

Bottom line: the conversion ratio is a function of luminaire efficacy, optical efficiency, thermal management, and the specific application standard. Don't let anyone sell you a "one-size-fits-all" conversion table. It doesn't exist.

Key Takeaways