Light emitting diode lightbulb

Lightbulbs – Which kind is best?

Background – Three Major Types of Light bulbs:

There are many different types of light bulbs for consumers to purchase. Three commonly purchased light bulbs are: Incandescent, Compact Flourescent light bulb (CFL) and Light Emitting Diode (LED). This article will examine the cost to own and operate these three types of light bulbs. At the end you will be equipped to understand the cost of lighting your home.

The Problem – Which Light bulb Should I Buy?

Every time a light bulb of mine goes out I invariably end up back at the question: Which light bulb should I buy?

For most standard screw in residential light bulbs there are three major options:

Incandescent Light bulb

Incandescent Lightbulb
An incandescent light bulb from a closet.

The incandescent light bulb is the grandfather of light bulbs. They have been used since long before I was born. They operate by running electricity through a filament which then produces the light. They reliably produce light for 1000 to 2000 hours. They function on dimmer switches without problem and they are cheap to buy.  Unfortunately they have some properties which may be undesirable. The major downsides to incandescent light bulbs are that they produce a significant amount of heat and they use more power.

Compact Fluorescent Light Bulb

Compact flourescent lightbulb from my house.
A compact flourescent light bulb from a fixture in my house.

What the heck is a CFL? Well a CFL is a twist (literally) on the more familiar fluorescent bulb (you know the long ones found in many businesses, schools, and other public buildings). These light bulbs operate by filling a glass tube with special gases and then running electricity through the tube. This causes the gas to illuminate producing the desired lighting. These bulbs can use different gasses or different coatings on the glass to emit light in different spectrums (the spectrum defines the colors of the light). Some spectrums found are ‘normal flourescent’, white, outdoor and even some to match incandescent light. A CFL is simply a fluorescent bulb twisted in many directions to produce a more compact shape.

The advantages of the CFL are a lower cost of operation for the same amount of light and they produce less heat (which eliminates the risk of a fire hazard that can occur with their incandescent counterparts) while producing the equivolent light. The problems with CFL’s are that they cost more than incandescent light bulbs to purchase and they contain mercury. Mercury can be a hazard under certain exposure conditions and it requires special disposal (see minimata disease or mad hatters disease for more info on mercury toxicity).

Light Emitting Diode Lightbulb

Light emitting diode lightbulb
A light emitting diode light bulb. I purchased this one in 2007 and this one took a while to warm up and get bright when turned on. As a result my wife didn’t like it so it is in a box (I’m hopping to sell her on the new generation versions which light up more instantly).

A LED light bulb functions by running electricity into a diode which then emits light. A diode is basically two different materials with differing electrical properties (specifically the conductance property). When encased in glass diodes can produce light. A screw in LED light bulb is a bunch of smaller LEDs emitting light together. The main advantages are that they produce light very efficiently which uses little power, produce little waste heat and they are mercury free. The biggest disadvantage is their initial purchase price is very high but they do operate for a long time.

The Solution – How to pick the best light bulb

This solution will focus on the financial aspect mainly. It should be noted that there are environmental and health reasons to not choose CFL and safty reasons (higher fire hazard risk) to not choose the incandescent. These risks should also be considered with regards to a specific lighting application and cost.

I visited a retailer website and found the following products (all three are 100-watt or 100-watt equivalent, that is they all produce about the same amount of light):

Incandescent: 48 pack of 100 watt incandescent light bulbs for $29.75, 750 hour life expectancy

CFL: 12 pack of 23 watt (100 watt equivalent) for $24.90, 10,000 hour life expectancy

LED: 1 pack 16 watt (100 watt equivalent) for $24.95, 40,000 hour life expectancy

Math

I am posting the math here so that you all may use the same formula when you are shopping for light bulbs. I will calculate it for the incandescent bulbs step-by-step and the other two I will just give the final answer.

 

Price Per Light Bulb

Take the price of the purchase ($29.75) divide it by the number of bulbs (48):

$29.75/48 = $0.61979 per bulb.

So each bulb costs about 62 cents.

 

Price Per Hour of Light Bulb

Take the Price Per Light Bulb ($0.61979) and divide it by expected life of the bulb in hours (750):

$0.61979/750 = $0.0008239 per hour of light bulb use

 

Now Convert The Watts to Kilowatts

Light bulbs are rated by how many watts they use. This means if you were to operate the bulb at maximum power for 1 hour that it would consume the rated number of watts. The incandescent bulb is rated at 100 watts. A kilowatt is 1000 watts. So the conversion is light bulb watts divided by 1000:

100/1000 = 0.1 kilowatts per hour (kWh)

 

Determine your electrical rate

You can ask whoever you pay your bill to for this, I pay $0.09445 per kWh for electricity.

 

Cost for 1-hour of electricity using the bulb

Simply take the use of the bulb per hour (.1 kWh) and multiple it by the cost per hour ($0.09445):

0.1 kWh * $0.09445 = $0.009445

Final Result

Finally add the 1 hour of light bulb cost ($0.0008239) and the 1 hour of electricity cost ($0.009445) to learn the total cost per hour of light with that light bulb.

$0.0008239 + $0.009445 = $0.0102689 per hour of light

So just slightly over 1 penny for the incandescent.

Here is all three:

Incandescent: $0.0102689

CFL: $0.0024

LED: $0.0021

 Conclusion:

At the end of the day it is worth it to do the math for your purchase because it could save you a lot of money over the long-term. In this case I found the LED bulbs to be the most cost effective. Cost is only one of many considerations to take for the purchase of lightbulbs.

If at your house there are 10 light bulbs turned on for 10-hours a day then the incandescent lightbulbs will cost about $1.03 per day. The CFL bulbs will cost about $0.24 cents. and the LED is about $0.21 cents. Over the course of a year using the LED bulbs (still at 10 bulbs for 10 hours each day) would save you $295.65 compared to the incandescent bulbs.

Here is a link to an excel spreadsheet you can download and type in all the values (the yellow squares can be changed). I have left my data from this review inside the sheet so that you may see it there for reference.

Tomorrow we will let those wheels keep on turning.