Light Fights: Fluorescents vs. HID

Light-Fights-HID-vs-FLUORESCENT

For our final installment in the Light Fight series we’re going to compare two bulbs that have been around for decades: fluorescents and high intensity discharge lamps (HIDs). Although there are newer technologies on the market, these bulbs have proven their abilities and continue to remain popular choices. Still, even if you know you want one of these tried-and-true bulbs, how do you decide between the two of them? Let’s try to make the decision easier by exploring these lights a little further…

Applications

Fluorescent and HID lights often compete in commercial applications where long-lasting, energy efficient bulbs are needed. They provide bright, consistent light over a large area and don’t need as much maintenance as ordinary incandescent bulbs. Therefore, they work well in circumstances where quality light is necessary but it’s difficult or dangerous to regularly replace bulbs. You’ll often find them in warehouses, sports arenas, streetlamps, bridges, tunnels, and in high-ceilinged buildings.

If you’ve read our earlier Light Fight posts you’ll know there are other bulbs suitable for such applications, but HIDs and Fluorescents are often pitted against each other, since they are both relatively inexpensive and established technologies.

 

Overview

Florescent and HID lamps are similar in that they both use ballasts and produce light through the process of electrons passing through gas. However, they differ in the ways they create energy and emit light. Here’s a brief explanation of how each bulb works:

Fluorescent Lights

Instead of using a filament (like an incandescent light), fluorescents rely on electrodes positioned on both ends of the bulb to send electricity through an inert gas (commonly argon) inside the tube. As the electricity flows, mercury inside the bulb absorbs the energy and releases it as a photon whenever it comes in contact with a moving electron. This photon becomes visible to the human eye after it passes through the bulb’s phosphorous coating.

 

High Intensity Discharge Light Bulbs

The most popular lights in the HID category include mercury vapor (MV), high pressure sodium (HPS), and metal halide (MH). They are all considered gas-discharge arc lamps that use electrodes and an ionized gas to create light. Light is produced from the arc whenever excited electrons change orbit and interact with the inert gas. HIDs also contain a secondary gas (sodium, mercury, halide), which not only designates the type of HID but also affects the color, intensity, efficiency, and lifespan of the bulb. Like fluorescents, they require a ballast which needs replacing over time.

 

Now let’s take a look at the side-by-side comparison…

 

HID & Fluorescents Compared

HID

Fluorescent

Energy Efficiency 40-100 Lumens/Watt 50 to 100 Lumens/Watt
Durability Fragile – has moving parts, glass bulbs, and filaments High quality fluorescents are heavy duty – have no filament, shock & vibration resistant
Lifetime 15,000 to 25,000 hours 30,000 hours and up (newest models)
Lumen Depreciation 30% to 40% at 2,000 hours 5% to 20% by rated life
Cold Tolerant – 40 F (may require longer warm up time at low temperatures) -10 F
Performance Needs 5-10 minute warm-up time, can flicker and glare Instant on
Color Temperatures Limited options (3000 to 5000 Kelvin) Multiple options (3000 to 6500 Kelvin)
Color Rendering 5 to 93 CRI Average 75 to 90 CRI
Dimmable? No Some
Warranty 1 to 2 years Usually 2 to 3 years
Cost Moderate upfront cost Low upfront cost

 

Solution

When evaluating HIDs versus fluorescents, you need to first consider the application.  Traditionally HID fixtures were installed in high ceiling applications and outdoor light fixtures.  Fluorescents on the other hand were used for general task lighting.   With all of the advances in fluorescent technology modern high intensity fluorescents (HIFs) deliver much more brightness than their predecessors, which means they are effective in the highest applications – a place only HIDs could go before.  In addition while HID was once considered the only choice for places with extreme temperatures, the amalgam technology in today’s fluorescents allows them to work in a wide range of temperatures.

With that in mind, we can see fluorescents have multiple advantages over HIDs, including better energy efficiency, lower lumen depreciation, faster start-up, dimming capabilities, durability, superior light quality, and less glare.

Although both lights have progressed significantly over the years, ultimately fluorescents are more cost-effective in the long term and provide better illumination. Even if HIDs could improve on energy efficiency, they still have to deal with their issues of warm-up and restrike delay (making them unsuitable for occupancy sensors) as well as their high lumen depreciation. These facts make fluorescents the winner in most applications; however, you may want to opt for HIDs for inexpensive, temporary lighting or if you still have working ballasts and aren’t ready for replacements.

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