LED vs High Pressure Sodium

What are High Pressure Sodium Lights?

High pressure sodium lights work by creating an electric arc through vaporized sodium metal, while additional materials and gases work to start the lamp and control the its color.

Street Lights With a Cell Phone
Street Lights With a Cell Phone

Benefits of High Pressure Sodium Lights

High Pressure Sodium area lights are most commonly seen on the road and in parking lots.

  • Color Temperature: Average 2000K, known for their warm yellow glow.
  • CRI: Disconcerting color rendering (CRI) that can inhibit vision at night and create darker shadows.
  • Bulb Failure: Prone to flickering and activation failure. At the end of the bulbs’ lives, they are more susceptible t turning on and off without input until they inevitably fail entirely.
  • Lumen: Maintain their luminance for 90% of their life span, and still maintain 80% emission at the end of their life.
  • Lifespan: High Pressure Sodium lights tend to have a lifespan averaging 24,000 hours. 
  • Bulb Angle: 360-degree bulb angle
  • Efficacy: High efficacy that is easily comparable to LED lights.
  • Price: High Pressure Sodium lights range between $5-$10.

The main benefit of using HPS is that they are the only light source with a similar efficiency to LEDs and maintain luminescence fairy well. They also do have great lifespans – around 24,000 hours – though this is significantly less than LEDs. They also are fairly cheap to purchase and cheap to maintain, and do not emit infrared or UV radiation.

Disadvantages of High Pressure Sodium

Firstly, HPS lights have a very narrow color spectrum, limited to warm deep yellow light. Although they are very popular for street lights, they don’t serve many other applications. They also have the worst CRI of any light source, falling around a 25 and like Metal Halides, require a warm-up period and may flicker or cycle on and off at the end of life.

Like Metal Halides, High Pressure Sodium lights are omnidirectional, which wastes light and makes them less efficient. They lose roughly 15% of their heat emissions which adds to their inefficiency.

HPS light costs differ based on the particular fixtures, but are cheap compared to LEDs. However, they are very fragile and operate with a glass bulb, making them unsafe for hazardous or explosive environments. This makes maintenance and replacement costs much higher than LEDs and more comparable to Metal Halides.

Street Light Cost
Street Light Cost

Advantages of LED Lights

ED area lights are top of the line bulbs. They are more efficient and have longer lifespans than High-Pressure Sodium lights.

  • Color Temperature: Variety of color temperature options providing better lighting solutions including cooler lights than High Pressure Sodium counterpart.
  • CRI: Higher CRIs for better color vision at night.
  • On/Off: Responds instantaneously to on/off input without any delays and can produce a steady non-flicker light throughout their entire lifespan.
  • Bulb Failure: LED lights slowly dim over time instead of flickering or turning on/off sporadically.
  • Lifespan: Range of 25,000 to 200,000 hours.
  • Bulb Angle: 180-degree bulb angle to preserve light efficiency and allow for target lighting over areas.
  • Efficacy: The most efficiency lights on the market with high efficacy averaging about 50 lumens/watt.
  • Price: LED lights are slightly more expensive than High Pressure Sodium lights at $10-$20.

The biggest differences between LED and High-Pressure Sodium lights are color temperature and CRI. LED lights have a wider variety of color temperatures along with higher CRIs.

LED Area Lights have a much easier immanence than High Pressure Sodium lights. LED lights have essentially no maintenance cost and must be changed rarely with infrequent monitoring. High Pressure Sodium lights have a high maintenance cost, because they require monitoring and more frequent replacement of both bulbs and parts.

Led Street Light
Led Street Light
FeatureHigh Pressure SodiumLEDWinner
Start UpHigh Pressure Sodium Lights have long warm-up time, usually around 15-20 minutes. LED fittings are instantly at full output.LED
LifetimeHPS Lights have good lifespans – around 14,000 hours – though this is significantly less than LEDs. LEDs last longer than any light source commercially available on the market. LEDs are typically 40,000 – 60,000 Hours.LED
DirectionalityLike Metal Halides, High Pressure Sodium lights are omnidirectional, which wastes light and makes them less efficient. They lose roughly 15% of their heat emissions which adds to their inefficiency.LED Chips are mounted on a circuit board, so depending on the configuration, usually 180 degrees. This is typically an advantage because light is usually desired over a target area (rather than all 360 degrees around the bulb).LED
Colour TemperatureHPS lights have a very narrow color spectrum, limited to warm deep yellow light. Although they are very popular for street lights, they don’t serve many other applications. They are well known for warm yellow glow, around 2200K.LEDs are available in a wide range of colour temperatures, generally from 2700K-6000K (ranging from ‘warm white’ to ‘daylight’)LED
Colour Rendering Index (CRI)HPS Lights have the worst CRI of any light source. Typically, they fall around 25.LEDs are available in the full range of CRI values. Typically, above 70 CRI.LED
EfficacyThe main benefit of using HPS is that they are the only light source with a similar efficiency to LEDs and maintain luminescence quite well. The losses associated with Omnidirectional light output rates them below LED.LEDs are very efficient relative to every lighting type on the market. Typical source efficiency ranges from 80 – 130 lumens/watt. Where LEDs really shine, however, is in their system efficiency (the amount of light that actually reaches the target area after all losses are accounted for).LED
Shock ResistanceHigh Pressure Sodium bulbs are relatively fragile.LEDs are solid state lights (SSLs) that are difficult to damage with physical shocks.LED

Resources: https://www.larsonelectronics.com/blog/2017/12/12/led-lighting/lighting-101-led-vs-metal-halide-high-pressure-sodium

https://www.homelectrical.com/advantages-led-vs-high-pressure-sodium-area-lights.6.html

https://decrolux.com/news/2019/high-pressure-sodium-vs-led-whats-the-difference-between-high-pressure-sodium-and-led-lights

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