Wednesday, May 15, 2013

The Light Bulb Efficiency Lie

With the economy still in questionable shape and people's real income stagnant, people are still looking for ways to cut their expenses. If your budget looks anything like ours, utilities are in the top five most expensive monthly expenditures. We are going to look at lighting of the home as a part of this expense. We are going to discuss how much of my family's electric bill goes to lighting and how little changing the bulbs in our home will effect this.

I will quickly admit that this was not the article that I was expecting to write. I was expecting to compare the different types of bulbs and tell you how long it would take for us to save the difference in price. After doing the math I have realized that lighting is the smallest part of our electric bill. I will still go over the savings, but not with the same zeal as before.

There are some terms we need to be familiar with when shopping for light bulbs.

Lumen: Quite simply a measure of brightness. The higher the number the brighter the bulb. Incandescent bulbs produce around 16 lumens per watt. A 100 watt incandescent bulb produces 1600 lumens.

Kelvin (K): This when used with light is the color scale. Interestingly Kelvin is a measure of temperature. The lower the number the "cooler" the color. A bulb with a 3100 K color will be called a soft white bulb. For me, the soft white looks very yellow. A bulb with a 6100 K color will be called a natural daylight. To me the natural daylight looks sort of blue. The natural daylight bulbs appear brighter even though it uses the same amount of energy.

Kilowatt Hour: Your electric bill is measured in kilowatts or kilowatt hours. A Kilowatt is 1000 watts. A Kilowatt hour is the amount of work 1000 watts can do. For the purpose of our discussion we will treat them as being exactly the same thing. A 100 watt incandescent bulb will burn a kilowatt in 10 hours.

Our electricity costs us 7.7 cents per kilowatt with a minimum bill of $14.50. To find what you are being charged per kilowatt, take your utility bill and look at it closely. Some of the bills will tell you exactly what you are being charged by kilowatt. Some you will have to figure yourself. You take the amount of your bill, subtract any taxes and fees. Then you take the amount that is left and divide it by the number of kilowatt hours used that month. This will give you cost of each kilowatt.

At 7.7 cents per kilowatt it costs us less than a penny an hour to run a 100 watt incandescent light bulb. With an average daily usage of 4 hours for several of the fixtures in our house and most of these having 3 bulbs per fixture. This means we are spending $25.87 a month only on lighting. I was quite shocked that this number was that small, but I figured it 3 times. This was figured on 28 bulbs running 4 hours per day, if you operate more lights than this the savings will be greater.

Incandescent: Incandescent bulbs have been the standard for a very long time. Incandescent bulbs have the shortest lifetime of any of the bulbs we will talk about today. They burn hot, so hot in fact that when I was a child I would melt crayons on the bulb of the light in my room. If there are any children reading this...Do Not Melt Crayons On Your Lamps. 

Halogen: Halogen bulbs have a slightly longer lifespan than the incandescent bulbs. A 100 watt equivalent burns 72 watts. If you changed out all 28 of the bulbs to halogens in my example, the monthly cost would go down to  $18.62 per month. Halogens burn very hot, so hot that I have considered changing all of the bulbs to halogens during winter because I believe the heat they produce would decrease heating costs. I would most certainly take any halogens out during summer months.

Compact Florescent (CFL): Compact Florescent bulbs have become the standard bearer of energy savings. They burn cool, last up to 3 times longer than an incandescent and a 100 watt equivalent only burns 24 watts. If we were to change all 28 of the bulbs to compact florescent bulbs instead of incandescent bulbs the price of lighting would go from $25.87 to $6.21. This is a significant savings. The biggest drawback for me is most of the CFLs contain mercury, which if not properly disposed of can be very damaging to the environment.

LED Light Emitting Diode: The newcomer to the market is the LED. LEDs are the most efficient, burn the coolest, and last the longest. Most of the models claim to be able to last 25 years. A 100 watt equivalent burns between 14 and 20 watts. For a bulb that would fit in most standard fixtures, we would need the 20 watt version. Changing all of the bulbs from incandescent to LEDs would drop the electricity cost for lighting from $25.87 to $5.17. This sounds great until you realize that a standard looking LED that would fit in most fixtures cost ranges between $33 and $50 each. If you have the money to drop on these bulbs it would be best for the environment and you wallet if you are willing to look extremely long term. Some estimates say that it will take 8 to 10 years to make up the difference in cost. My estimate is right at 4 years with the exact same usage as I figured. In our household this is not possible because our lighting usage goes way down in the summer so this number would be much greater.

Conclusion: The 100 watt light bulb being phased out is a way to act like you are doing something without actually doing so. For most households lighting is the smallest part of their electric bill. If you are wanting to really reduce your electric bill adjust your thermostat. Heating and cooling is estimated to be as much as 20 percent of your total utility bill. Be aware of how much television you are watching. The average electricity a television uses is 300 watts per hour. Use a clothes line to dry some of your clothes.The average clothes dryer uses 4400 watts per hour. There are more and better ways to save on your electric bill. Having said all of this, I am still looking forward to the price of LED bulbs coming down and I want to have them in my home, but I am not willing to pay the difference.

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