Lighting Comparison: LED vs Fluorescent and CFL

2020-01-01

Fluorescent (or CFL):

What is a Fluorescent Light or a CFL?

Fluorescent lights are a specific type of gas-discharge light (also known as a high intensity discharge, HID, or arc light). CFL is an acronym that stands for compact fluorescent light. Standard fluorescent lights are available in tubes (generally 48 to 84 inches in length). CFLs are much smaller. They are still tubes but they are, as the name implies, “compact.” CFLs were designed to replace standard applications for incandescent bulbs as they are both more efficient and longer lasting. Fluorescent lamps produce light by converting ultraviolet emissions with a fluorescent coating on the inside of the tube. UV radiation is generated in the first place by an electrical charge that is run through the inert mercury glass internal to the bulb. The gas is excited by the electricity and releases ultraviolet radiation as a consequence. Fluorescent lights require ignition, which is typically provided by a voltage pulse or a third electrode (an additional metal part) internal to the bulb. Starting is relatively simple with small tubes but can require significant voltage with larger lights. Fluorescent lighting used to require a “warm-up” period in order to evaporate the internal gas into plasma, but now there are several near-instantaneous starting technologies for fluorescent light (those include “quick-start,” “instant start,” and “rapid-start”). Additionally, as the light heats up it requires additional voltage to operate. Voltage requirements in fluorescent bulbs are balanced by a ballast (a magnetic device in older bulbs and an electrical one in newer fluorescent technology).  As the fluorescent light ages, more and more voltage is required to produce the same amount of light until eventually the voltage exceeds the fixed resistance provided by the ballast and the light goes out (fails). Fluorescent lights become less and less efficient over time because they must use more and more voltage to produce the same lumen output as the light degrades. 

What’s the Upside to Fluorescent Lights?

Fluorescent technology has been around for more than 100 years and it generally represents a high efficiency way to provide lighting over a vast area. The lights are much more efficient as well as longer lasting than incandescent bulbs, however, they fail in both categories when compared to LED.

What are the Major Deficiencies in Fluorescent Lights?

Among the deficiencies in fluorescent lighting are the following:

1. Fluorescent lights contain toxic mercury. Mercury as well as the phosphor inside the bulbs are hazardous materials that present a waste disposal issue at the end of a light’s life. Broken bulbs release a small amount of toxic mercury as a gas and the rest is contained in the glass itself.  
2. Fluorescent lights age significantly if they are frequently switched on and off. Typical lamp life for a CFL is about 10,000 hours but this can degrade as a consequence of frequent switching (turning on and off). Burning life is extended if lamps remain on continuously for long periods of time. It’s worth thinking about in the event that you are using CFLs in conjunction with motion sensors that frequently activate and time out.
3. Fluorescent lights are omnidirectional. Omnidirectional lights produce light in 360 degrees. This is a large system inefficiency because at least half of the light needs to be reflected and redirected to the desired area being illuminated. It also means that more accessory parts are required in the light fixture itself in order to reflect or focus the luminous output of the bulb (thus increasing unit costs).

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Among the minor deficiencies in fluorescent lighting are the following:

1. Older fluorescent lights have a brief warm-up period. Once the arc is ignited it melts and evaporates metal salts internal to the device. The light doesn’t arrive at full power until the salts are fully evaporated into plasma. This is corrected in many newer models that utilize “rapid start” or similar technologies.
2. Fluorescent lighting emits a small amount of UV radiation. Ultraviolet light is known to cause fading of dyed items or paintings exposed to their light.
3. Fluorescent lights require a ballast to stabilize the light. In the event that there is a minor flaw in the ballast the light may produce an audible hum or buzz.

Where are Fluorescent Lights Commonly Used?

Common applications for fluorescent lighting include warehouses and schools or commercial buildings. CFLs are also used as a replacement for incandescent lights in many residential applications.

LED:

What is a Light Emitting Diode (LED)?

LED stands for light emitting diode. A diode is an electrical device or component with two electrodes (an anode and a cathode) through which electricity flows - characteristically in only one direction (in through the anode and out through the cathode). Diodes are generally made from semi-conductive materials such as silicon or selenium - solid state substances that conduct electricity in some circumstances and not in others (e.g. at certain voltages, current levels, or light intensities). 

When current passes through the semiconductor material the device emits visible light. It is very much the opposite of a photovoltaic cell (a device that converts visible light into electrical current).

What’s the Major Upside to LED Lights?

There are four major advantages to LED lighting: 

1. LEDs have an extremely long lifespan relative to every other lighting technology (including fluorescent lights). New LEDs can last 50,000 to 100,000 hours or more. The typical lifespan for a fluorescent bulb, by comparison, is 10-25% as long at best (roughly 10,000 hours).
2. LEDs are extremely energy efficient relative to every other commercially available lighting technology. There are several reasons for this, including the fact that they waste very little energy in the form of infrared radiation (much different than most conventional lights to include fluorescent lights), and they emit light directionally (over 180 degrees versus 360 degrees, which means there are far fewer losses from the need to redirect or reflect light).
3. Very high light quality
4. Very low maintenance costs and hassle

What are Minor Upsides to LED Lights?

In addition to the major advantages, LED lights also offer several smaller perks. These include the following:

1. Accessories: LEDs require far fewer accessory lamp parts.
2. Color: LEDs can be designed to generate the entire spectrum of visible light colors without having to use the traditional color filters required by traditional lighting solutions. 
3. Directional: LEDs are naturally directional (they emit light for 180 degrees by default).
4. Size: LEDs can be much smaller than other lights.
5. Warm-Up: LEDs have faster switching (no warm-up or cool-down period).

What’s the Downside to LED Lights?

Considering the upsides, you might think that LED lights are a no-brainer. While this is increasingly becoming the case, there are still a few trade offs that need to be made when you choose LED.

In particular, LED lights are relatively expensive. The up-front costs of an LED lighting project are typically greater than most of the alternatives. This is by far the biggest downside that needs to be considered. That said, the price of LEDs are rapidly decreasing and as they continue to be adopted en masse the price will continue to drop.

Where is LED Commonly Used?

The first practical use of LEDs was in circuit boards for computers. Since then they have gradually expanded their applications to include traffic lights, lighted signs, and more recently, indoor and outdoor lighting. Much like fluorescent lights, modern LED lights are a wonderful solution for gymnasiums, warehouses, schools, and commercial buildings. They are also adaptable for large public areas (which require powerful, efficient lights over a large area), road lighting (which offer significant color advantages over low and high pressure sodium lights), and parking lots.

Further Qualitative Comparison 

What’s the Difference Between Fluorescent and LED Lights?

The two different technologies are entirely different methods of producing light. Fluorescent bulbs contain inert gas within the glass casing while LEDs are a solid state technology. Fluorescent lights produce UV radiation and then convert it into visible light through the use of a phosphor coating inside the bulb. LEDs emit electromagnetic radiation across a small portion of the visible light spectrum and don’t waste energy by producing waste heat or non-visible electromagnetic radiation (such as UV). There is such a thing as an IRED (infrared emitting diode) which is specifically designed to emit infrared energy.  

Why Would LEDs Put Fluorescent Lights Out of Business?

In the last few years LED efficiency has surpassed that of fluorescent lights and its efficiency improvements are progressing at a much more rapid rate. Further, fluorescent lamps require the use of a ballast to stabilize the internal current that produces light. When the ballast has a minor imperfection or is damaged, the light can produce an audible buzzing noise. Other shortcomings include the following:

• Fluorescent lights can cause retrofit problems due to their elongated shape.
• Fluorescent lights can present waste disposal issues due to their reliance on mercury.
• Fluorescent lights are non-directional, meaning that they emit light for 360 degrees. As you might expect, a large portion of this light is wasted (for example, that portion that is directed at the ceiling).

Why would LEDs Put Compact Fluorescent Lights (CFLs) Out of Business?

As good as fluorescent light efficiency has become, LED is better (and continues to improve at a more rapid pace). As long as fluorescent lights last, LED lights last much longer. Further, fluorescent lamps require the use of a ballast to stabilize the internal current that produces light. When the ballast has a minor imperfection or is damaged, the light can produce an audible buzzing noise. Other shortcomings include waste disposal issues (due to CFL's reliance on mercury), and non-directional light generation. Non-directional light generation is a bigger deal than you might think. For example, light that is being directed at the ceiling rather than the room is wasted light. Therefore, CFL (as well as the related standard fluorescent bulbs) might have good “source efficiency” (i.e. it looks good on paper), but will fall short of LED when it comes to the more important measure: “system efficiency” (actual efficiency in real world applications).