Eugene is a qualified control/instrumentation engineer Bsc (Eng) and has worked as a developer of electronics & software for SCADA systems.
What Lighting Should I Use?
Did you know that a "normal" incandescent light bulb only converts about 5% of the electricity used into useful light? The remaining 95% ends up as heat. There are lots of other options for home lighting which are much more efficient, however modern LED lamps are by far the best in terms of energy efficiency. In this guide we'll examine the pros and cons of each type of lighting technology and discover what's so good about LEDs.
What Difference Does It Make What Lighting I Use?
Well basically some lighting types are more efficient than others and use less electricity while producing the same light output. However there are other issues to consider when buying lamps and light fittings such as the initial cost of lamps/light fitting, lifetime of bulbs and the color of light produced.
Explanation of Lighting Terms
- Lamp. The component of a light fixture which actually produces light output.
- Ballast or Switchgear. The electrics/electronics used for controlling the switch on and regulation/limiting of current passing through a lamp
- Lumens. The output light flux from a lamp. A traditional 100 watt incandescent bulb gives out about 1500 lumens of light
- Candela or millicandela. The brightness of a lamp. A reflector at the back of a lamp (eg on a floodlight or car headlamp) increases the brightness in the forward direction, even though the lumens output of the lamp stays the same.
- Luminous Efficacy. Output in lumens per watt of electrical power input
- PIR. Passive Infra RED. A technology used in switches for turning on a light when someone walks in front of the PIR sensor
- Incandescent Lighting. A lighting technology that produces light from a material heated to a very high temperature
- Discharge Lighting. Producing light by passing an electric current through a gas
What Are the Different Types of Lighting Technology?
There are three broad classes of lighting technology
What Is Incandescent Lighting?
Incandescent lighting is based on the principle of heating a metal to a high temperature. At temperatures of over 1000C, metals glow white hot.
- Standard incandescent bulb
- Quartz halogen tube
- Halogen bulb
- Halogen spotlight
Standard Incandescent Bulb
This is the original form of lighting which has been used in the home for over a hundred years. Bulbs or lamps consist of a glass envelope containing a filament made of tungsten or similar metal of high electrical resistance and melting point. An electrical current is passed through the filament which glows white hot and radiates light and heat. The glass envelope is filled with an inert gas such as argon to isolate the filament from oxygen in the air and prevent it from burning out.
Incandescent bulbs are made in all sorts of shapes, sizes, wattages and base styles; bayonet cap (BC) and Edison screw (ES). They are also the least expensive type of lamp and don't require any special holders or electronic/electrical switch gear. They can be plugged into a simple holder. However they are woefully inefficient in terms of light output versus energy input. An incandescent bulb converts most of the electricity input to heat - typically about 95%. So these types of lamps are basically glorified heaters! Lifespan of a bulb is the shortest of all types of lighting at approx 1000 hours.
Quartz Halogen Lamps
These take the form of a tube about 1/2 an inch in diameter and from 3 to 5 inches long made of quartz glass. A tungsten filament is mounted internally in an inert gas to which a small amount of a halogen such as bromine or iodine is added. In a normal incandescent lamp, tungsten vapor "evaporates" from the filament blackening the glass envelope, reducing the light output and the lifespan of the lamp. This phenomenon would become more severe as the temperature of the filament increases. An object becomes more efficient at radiating light as it becomes hotter. So it is desirable to increase the efficiency of a lamp by increasing the filament temperature .The added halogen combines with evaporated tungsten producing a halide, effectively "mopping up" the tungsten and keeping the quartz clear. So the lamp can be run at a much higher temperature and this increases light output for a given wattage. The quartz glass envelope is important in order to withstand high temperatures, and the increased pressure also reduces tungsten evaporation from the filament. These lamps are commonly used in exterior floodlights (e.g. 150, 300 and 500 watt types). The disadvantage is that the lighting fixture can become quite hot and must be kept at a minimum distance from flammable materials to reduce the danger of fire. The lamps are prone to failure also as dampness condensing on the surface of the tube due to moisture in the fitting, or from the lamp being touched during installation, can cause failure. This is because hot spots caused by contamination can crystallize the glass making it leak or rupture.
These are shaped like standard incandescent bulbs and available in similar wattages and shapes. However they contain a quartz halogen capsule. They use about 70% of the energy of a standard incandescent bulb. The commonly available 50 watt spotlight bulbs are of the halogen type.
These are usually 50 watt and are commonly available in a light fixture which takes 3 or 4 lamps which can be pointed in different directions. So they can be used in a kitchen for instance for concentrating light onto a worktop.
What's the Cost of Running a Standard Light Bulb?
If a bulb is switched on for about 10 hours per day in the winter, and 4 hours per day in the summer, this works out at 7 hours per day on average for the whole year.
So this is 365 * 7 = 2555 hours per year.
Cost per kilowatt hour (kWh) or unit is about 12 cents.
Assume the bulb is 100 watt.
Cost of running bulb = (power in watts / 1000) x number of hours running time x cost per unit
= (100/1000) x 2555 x 12
What Is Discharge Lighting?
Discharge lighting works on the principle of passing an electric current through a gas. This ionizes the gas, and the electrons give out light as they return to their non-excited state. This is similar to how an electrical spark from a spark plug or lightning produces light.
- Sodium vapor
- Metal halide
Fluorescent tubes are a type of discharge lamp. They contain a gas and mercury vapor. When a fluorescent lamp is switched on, a current passes through filaments at the end of the tube causing them to glow. This produces electrons in the vicinity of the filaments. A high voltage pulse then "strikes" the tube causing electrons to be accelerated down the tube. These electrons collide with atoms of the mercury vapor and excite them, making their electrons jump to higher orbits and then fall back, radiating UV light in the process. This radiation hits the inner surface of the tube which is coated with a phosphor and the UV is converted to visible light.
Fluorescent lamps give 4 to 5 times more light output per watt compared to incandescent bulbs. However the tubes are more expensive and special fixtures incorporating switchgear for controlling the lamps are required, adding to the cost. In the medium term, fluorescent lighting pays for itself because of the lower running costs. So it is used widely in the workplace and stores. The disadvantage of fluorescent lighting is that the spectrum of the light veers towards the green and blue end of spectrum unlike the warm glow of incandescent lighting. However tubes are commonly available which somewhat correct this at the expense of light output. Another disadvantage is that the flicker of fluorescent lighting can be irritating to some people and could trigger epilepsy or migraine in susceptible individuals. Newer type electronic ballasts in fixtures raise the flicker frequency and this may lessen the potential for this occurring.
Fluorescent tubes are available from 4 inches in length to 8 feet long. Variations in shape are available e.g circular shapes.
CFL (Compact Fluorescent Lamp)
A CFL is basically a folded up fluorescent tube. The plastic section of the lamp incorporates the switchgear. This is electronic, and the switching frequency is high, minimizing flicker, unlike older type inductive ballasts. CFLs act as "drop in replacements" for standard incandescent lamps, and like fluorescent tubes, their efficiency is higher than that of incandescents. So a 20 watt CFL is equivalent to a 100 watt incandescent (In practice it is closer to about 90 watt). CFLs have dropped in price over the years as production and demand has increased. This is due to mandatory bans on widespread incandescent lamp use in some countries in order to reduce energy consumption.
Sodium Vapor Lamps
Sodium lighting will be familiar to you in the form of the orange/yellow lamps used to light our streets. This is another form of discharge lighting just like fluorescent lamps. The tube is made of borosilicate glass to withstand pressure and temperature and contains some sodium metal, neon and argon. When the lamp is switched on, the sodium vaporises and an arc is established. There are various types of sodium lamps; high pressure. low pressure, SON, SOX etc. Sodium lighting has the highest efficiency of all lighting. This is due to the fact that the light output is in the yellow range of the spectrum and the human eye is most sensitive in this region. However there are several disadvantages. Firstly it takes several minutes for a lamp to reach full brightness, so switch on by a PIR is not an option. Also switchgear is necessary to control the lights. Because the light output is yellow, this can be a problem where color rendition is important. Sodium floodlights are advantageous for lighting up a yard or garden for instance because of the low running cost, and the light can be switched on at dusk by a photoelectric switch.
Metal Halide Lighting
Another form of discharge lighting. Not quite as efficient as sodium, but the light output is white in color so it is useful for lighting up a yard for instance when color rendering is necessary. The lamps contain gases such as xenon and a mixture of mercury and metal halides. Metal halide fittings are used for flood lighting sports stadiums, car parks, store yards etc. and as display lighting in stores. The lamps are also used in car headlights (the ones which appear slightly bluish)
What Is LED Lighting?
These devices work on the principle of light emission produced by passing a current through various types of semiconductor material. The lamps are made up of a structure onto which hundreds of LEDS are bonded. LED lighting is steadily replacing other types in numerous applications such as domestic lighting, workplace and street illumination and vehicle lighting.
What Are the Advantages of LED Lights?
LED lamps/bulbs offer many advantages.
- They are even more efficient than CFL and use 5 times less electricity than a standard incandescent bulb.
- They run cool and produce less heat output than any other type of lighting.
- They are rugged and don't have a fragile glass envelope unlike a CFL or incandescent lamp.
- They are available in a multitude of colors.
- They are easily dimmable.
- LED lamps have a theoretical lifetime of 50000 hours, 50 times that of an incandescent light bulb.
Disadvantages of LED lamps
- At present, they are quite expensive compared to incandescent bulbs, but costs are falling all the time as production and demand increases.
- Lighting is somewhat more directional so less output from the back of standard replacement LED bulbs to illuminate a ceiling.
- Bulbs can't be used inside appliances that become hot e.g. ovens.
LED lamps are available as drop in replacements for standard incandescent bulbs, halogen spotlights, halogen tubes in floodlights and fluorescent tubes.
A 100 watt incandescent bulb can cost up to $30 a year to run, if switched on for about 7 hours on average per day. An LED lamp will cost only about 1/5 of this to run.
Over the years I replaced my incandescent bulbs with CFLs to save energy, but since they were coming to the end of their 5 year lifespan and becoming dim, I decided to upgrade to LED technology.
These LED lamps by Philips are rated at 14W, but produce the same amount of light as a 100W incandescent, so that's an 85% saving in energy. The light output spectrum is classed as daylight (similar to a cool white fluorescent lamp), but bulbs are also available with a soft white cast if you prefer a warmer more traditional "yellowish" glow like that produced by an incandescent lamp. However daylight bulbs always appear brighter than soft white.
These lamps are also available in 60 watt versions.
Outdoor Lighting and PIR Sensors
When controlled by a PIR sensor which detects someone walking by, a lamp should light up instantly. Bulkhead or similar light fittings can be fitted with incandescent or LED lamps which are suitable for this application
|Lamp Type||Luminous Efficacy (lumens/watt)||Color of Light||Advantages||Disadvantages|
10 - 15
Least expensive lighting, no switchgear needed, reach full brightness instantly
Low efficiency, shortest lifespan (1000 hrs)
15 - 20
Relatively cheap - no switchgear needed - more efficient than standard incandescent
Run very hot
35 - 60
50 - 100
Warm White, Cool White
Very efficient, run relatively cool, 5000 hr life span
More expensive than halogen or incandescent, special fixture needed. Contain mercury vapor, so must be disposed of properly.
100 - 200
Very efficient, run cool, drop in replacement for incandescent bulbs, very long lifespan (50000hrs), reach full brightness instantly
Expensive at present
80 - 200
Was the most efficient form of lighting, but LED now better.
Expensive, switchgear needed, take a long time to reach full brightness, not suitable when it is necessary to differentiate between colors
50 - 90
Very efficient but not as efficient as sodium, light output is white
Expensive, switchgear needed, take time to reach full brightness
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
Question: Can a sodium vapor bulb be replaced with a CFL bulb?
Answer: No. The ballast/switchgear is totally different. However, if all the electrics in a fitting are stripped out or isolated and the lamp holder is powered directly by mains, it could be possible.
Question: I don't see halogen bulbs in the comparison chart, only quartz halogen. Are quartz halogen bulbs the same as halogen bulbs?
Answer: Yes, they're the same. The glass envelope is made of quartz.
© 2012 Eugene Brennan
Eugene Brennan (author) from Ireland on May 31, 2020:
The only thing I don't like about LED lamps is that the amount of light emitted from the rear is a lot less. So for a single lamp light fixture/lamp holder, very little light is thrown up to the ceiling and diffused downwards.
All our street lamps are being changed from sodium to LED in a programme that will last a couple of years.
Dan Harmon from Boise, Idaho on May 31, 2020:
Like you, I have replaced very nearly all my lights with LED lamps. They were, for the most part, fluorescent (with the except of a very few such as the one in the range oven) and as they wore out I replaced them. Even the fluorescent tubes have been replaced with LED tubes.
I'm also converting my RV from incandescent and fluorescent to LED. As I "dry camp", without electricity, much of the time it extends the life of the batteries by a huge amount.
Louise89 on March 16, 2020:
Very helpful, thanks!
Eugene Brennan (author) from Ireland on April 26, 2016:
It certainly is Leonardo, and LED is the way of the future. Prices should drop drastically in the next few years.
Thanks for the comment!
Leonardo David from Honduras on April 26, 2016:
I believe LED is the most cost-effective type of lighting in the long term. Sure, the upfront cost is higher, but it lasts 25 times longer than a standard incandescent bulb... without being 25 times more expensive!
Eugene Brennan (author) from Ireland on June 16, 2015:
You're welcome! LED is the future of lighting, being much more efficient energy wise, and less fragile than incandescent or discharge lighting. The lamps in this case incorporate a glass envelope which is always prone to breakage if not enclosed in a fixture. There are still issues with heat dissipation from LEDs. Incandescent lamps were made from glass, metal and ceramic, so heat wasn't a problem. LED lamps are mostly plastic though, so adequate heat sinking needs to be incorporated into the design of the products to avoid melting. Maybe efficiency will increase with new semiconductor materials being developed, resulting in less heat dissipation, so this will be less of an issue.
quicksand on June 16, 2015:
I wanted to replace the 30 watt incandescent bulb on my desk with a low wattage LED bulb. So thanks for helping me to decide. :)
Eugene Brennan (author) from Ireland on June 15, 2015:
I don't think light radiation in itself is harmful to the eye, at least in the visible range of the spectrum. However UV light is damaging to the eye, which is why discharge lighting and halogen bulbs which can radiate at these wavelengths incorporate filters which absorb UV.
Very bright light will damage the cells in the retina. This is why a laser is dangerous, because even though the overall power of the beam may be low, light is concentrated into a narrow beam with a high luminous intensity over a narrow angle. Also the energy is confined to a narrow spread of wavelengths in the spectrum which also increases intensity.
I'm just guessing here, but incandescent and LED are probably the safest, with discharge lighting least safe because of a certain amount of UV passing through filters.
quicksand on June 14, 2015:
Which type of light do you think is least harmful to the eye?
Eugene Brennan (author) from Ireland on June 14, 2015:
The candle power was an old unit of light intensity which was replaced by the candela. In the days of candles, I suppose it was a good way of expressing brightness of gas lighting and the new fangled electric lightning by referencing a familiar light source.
quicksand on June 14, 2015:
My father used to refer to a 100 watt bulb as a 100 candle power bulb!
Eugene Brennan (author) from Ireland on January 04, 2014:
Thanks Jan, glad you liked it and it en - light - ened you on the various options available!
Janis Leslie Evans from Washington, DC on January 04, 2014:
So glad I stopped by to read this hub, eugbug. This was very informative in teaching me about the different types of light bulbs, advantages and disadvantages, and energy efficiency. It is extremely well-written and easy for the average person to read and gather enough information about choosing a bulb and making the switch to energy efficiency. Thanks for the extra info about iridescent bulbs ;) Voted up, useful, and interesting.
Eugene Brennan (author) from Ireland on December 07, 2012:
Thanks for the comment! LED lights are quite expensive at present but the cost will drop in the next couple of years. Hopefully the promised 50000 hour lifespan, which is equivalent to 17 years at 8 hours a day, is realistic. Nothing is designed to last nowadays so this is probably a bit optimistic!
tipstoretireearly from New York on December 07, 2012:
Excellent chart to compare and contrast the different lighting options. I'm looking forward to buying LED lights once the prices drop a little more.