|Date||April 08, 2019|
Both Metal Halide and High Pressure Sodium bulbs are part of the HID family of bulbs. The primary visual difference between them is that metal halide light is white and the light emitted from a High Pressure Sodium bulb is amber orange. The lamp works by creating an electric arc through vaporized sodium metal. Other materials and gases are used to help start the lamp or control its colour.
High Pressure Sodium Vapor (HPS) lights are a specific type of gas-discharge light (also known as a High Intensity Discharge, HID or arc light). The principal difference between low and high pressure sodium lights is the operating pressure inside the lamp. As indicated by the name, “high” pressure sodium vapor lights operate at a higher internal pressure. The arc tube is made of aluminum oxide and the sodium metal is combined with several other elements like Mercury which counter-balances the yellow glow with some white to light blue emissions.
|Feature||High Pressure Sodium||LED||Winner|
|Start Up||High Pressure Sodium Lights have long warm-up time, usually around 15-20 minutes.||LED fittings are instantly at full output.||LED|
|Lifetime||HPS 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|
|Directionality||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.||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 Temperature||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 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|
|Efficacy||The 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 Resistance||High Pressure Sodium bulbs are relatively fragile.||LEDs are solid state lights (SSLs) that are difficult to damage with physical shocks.||LED|