Correlated Color Temperature
LEDs are available in a wide range of color temperatures, typically spanning from 2200K to 6000K, covering everything from “warm” yellow to “cool” blue light.
Metal halide lamps produce a very cool white light and are available in color temperatures as low as 3000K. Some metal halides even reach extremely cool temperatures up to 20,000K.
WINNER: –
CRI (Color Rendering Index)
The CRI of LEDs depends on the specific light, but a broad spectrum is available, generally ranging from 65 to 95.
Metal halides are among the best sources of high-CRI white light on the market.
WINNER: Metal Halide
Cycling (Turning On/Off)
LEDs are ideal for frequent on/off operation because they respond almost instantly, with no warm-up or cool-down period, and they provide steady, flicker-free light.
Metal halide lights, in contrast, have long warm-up times. Many stadiums historically relied on metal halide lamps, but these bulbs can take 15–30 minutes to reach full operating power.
WINNER: LED
Dimming
LEDs are very easy to dim, with options ranging from 100% down to 0.5% of their light output. Dimming works by either reducing the forward current or modulating the pulse duration. Note that LED lights are not compatible with traditional incandescent dimmers, which lower the voltage. To dim LEDs, you need compatible LED dimmer switches.
Metal halide lights can be dimmed using different electric or magnetic ballasts, but this process alters the voltage supplied to the lamp and can change the light characteristics. Generally, metal halides are less efficient when operated below full power, and in some cases, dimming may even shorten the lamp’s lifespan.
WINNER: LED
Directionality
LEDs emit light over 180 degrees, which is typically an advantage since light is usually needed over a specific target area rather than in all directions. This concept relates to measurements like “useful lumens” or overall system efficiency.
Metal halide lights, in contrast, are omnidirectional, emitting light in 360 degrees. Much of this light must be reflected or redirected, resulting in losses and lower system efficiency.
WINNER: LED
Efficiency
LEDs are very efficient compared to all other lighting types on the market and exceptionally efficient relative to incandescent bulbs. Typical source efficiency ranges from 37 to 120 lumens per watt. Where LEDs truly excel, however, is in system efficiency—the amount of light that actually reaches the target area after accounting for all losses. Most LED system efficiencies exceed 50 lumens per watt.
Metal halide lights have moderate efficiency, with source efficiency typically between 75 and 100 lumens per watt. They fall behind LEDs primarily because their system efficiency is much lower (less than 30 lumens per watt) due to losses from omnidirectional light output and the need to redirect light to the desired area.
WINNER: LED
Efficiency Droop
LED efficiency decreases as current increases. Heat output also rises with additional current, which can reduce the device’s lifetime. Overall performance drop is relatively minor, with about 80% of output typical near the end of life. Recent research has identified the causes of droop in LEDs, and these advances are expected to further reduce losses.
Metal halide lights also experience efficiency losses as they age, requiring more current to maintain the same light output. These losses are greater than those in LEDs, and the degradation occurs over a shorter period.
WINNER: – (Note: Recent advances in LEDs are likely to further improve their droop performance)
Emissions (In Visible Spectrum)
LEDs produce a very narrow spectrum of visible light, without the energy losses associated with irrelevant radiation types such as infrared (IR) or ultraviolet (UV), or with heat typical of conventional lighting. This means that most of the energy consumed by LEDs is converted directly into visible light.
Metal halide lights, in contrast, emit significant amounts of both IR and UV radiation.
WINNER: LED
Ultraviolet & Infrared
LEDs: None
Metal Halide Lights: Emit IR radiation, which is wasted energy for standard illumination purposes. They also emit UV radiation and require built-in filters to prevent these emissions from escaping into the environment. These filters protect surfaces from fading, prevent damage to fixtures, and reduce risks to humans and animals, such as severe sunburn or arc eye.
WINNER: LED
Failure Characteristics
LEDs fail gradually, dimming over time rather than suddenly. Since most LED luminaires contain multiple light emitters, the loss of one or two diodes does not constitute failure of the entire fixture.
Metal halide lights, on the other hand, exhibit a phenomenon known as cycling, where the lamp repeatedly turns on and off without human intervention before eventually failing completely. Because of this, metal halide lamps in many applications—such as sports stadiums—must be replaced before reaching the end of their rated lifespan.
WINNER: LED
Foot Candles
Foot candle is a measure of the amount of light reaching a specific surface area, rather than the total light output of the source (luminous flux).
LEDs are very efficient relative to other lighting types, with typical source efficiency ranging from 37 to 120 lumens per watt. Where LEDs truly excel is in system efficiency—the amount of light that actually reaches the target area after all losses. Most LED system efficiencies exceed 50 lumens per watt.
Metal halide lights are efficient compared to incandescent bulbs, with source efficiency between 75 and 100 lumens per watt. However, they fall behind LEDs in system efficiency (less than 30 lumens per watt) due to losses from omnidirectional light output and the need to redirect light.
WINNER: –
(Note: Foot-candle ratings are highly application-specific, so relative performance can be difficult to quantify.)
Heat Emissions
LEDs emit very little heat. The main potential drawback arises when LEDs are used outdoors in snowy conditions. Traditional lights, like HID lamps, can melt snow that falls onto them. This issue is typically addressed for LEDs by using a visor or angling the light downward toward the ground.
Metal halide bulbs, in contrast, emit a significant amount of heat—roughly 10–15% of the total energy consumed. While this can occasionally be beneficial, it generally represents wasted energy, as the primary purpose of the light is to produce illumination, not heat.
WINNER: LED
Life Span
LEDs have the longest lifespan of any commercially available light source. While actual lifespans vary, typical values range from 25,000 to 100,000 hours or more before a lamp or fixture needs replacement.
Metal halide lights have a longer lifespan than older technologies like incandescent bulbs, but they are far shorter-lived compared to LEDs. Typical lifespans range from 6,000 to 15,000 hours, and in many cases, metal halides must be replaced before the end of their rated life to prevent serious degradation effects such as color shifts or cycling.
WINNER: LED
Lifetime Cost
LED lighting has relatively high initial costs but low lifetime costs. The technology typically pays back the investor over time, mainly through reduced maintenance costs (dependent on labor) and, to a lesser extent, energy efficiency improvements (dependent on electricity costs).
Metal halide lights are relatively inexpensive to purchase but costly to maintain. Multiple replacements and associated labor are usually required to match the lifespan of a single LED light.
WINNER: LED
Maintenance Costs
Due to their long operational lifetimes and minimal replacement frequency, LEDs have the lowest maintenance costs on the market.
Metal halide bulbs require regular relamping and ballast replacement, along with labor to monitor and replace aging lamps multiple times over the typical lifespan of a single LED.
WINNER: LED
Upfront Costs
LED lights are relatively expensive but vary by specifications. A typical 100W-equivalent LED costs between $10 and $20.
A 100W metal halide bulb ranges from $10 to $30, depending on specifications.
WINNER: –
Shock Resistance
LEDs are solid-state lights (SSLs) and are highly resistant to physical shocks.
Metal halide bulbs are relatively fragile, and broken bulbs require special handling and disposal due to hazardous materials such as mercury.
WINNER: LED
Size
LEDs can be extremely small (less than 2mm in some cases) and can also be scaled up, making them suitable for a wide variety of applications.
Metal halide bulbs can be small but are typically not produced below roughly one centimeter in width. Their size is generally constrained by required wattage and light output.
WINNER: LED
Cold Tolerance
LEDs: down to –40°C and turn on instantaneously
Metal Halide: down to –40°C
WINNER: LED
Heat Tolerance
LEDs operate well at normal indoor and outdoor temperatures, up to around 100°C. High temperatures can degrade performance, and effective heat sinking is required, especially near sensitive components.
Objective data for metal halide performance at high temperatures is not readily available.
WINNER: –
Warm-Up Time
LEDs reach full brightness nearly instantly.
Metal halide lamps require a noticeable warm-up period, which can range from 15 to 20 minutes in applications such as stadium lighting.
WINNER: LED
Warranty
LEDs: typically 5–10 years
Metal Halide: typically 1–2 years
WINNER: LED
