Where did this come from?

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mcclary's electrical

mcclary's electrical

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Location
VA
This is word for word out of UGLY's 2008

Changing incandescent lamp to energy saving lamp


A 100 watt incandescent lamp is to be replaced with a 26 watt enrgy saving lamp that has the same lumens. If the cost per hour kilowatt-hour is 15 cents, how many hours would the new lamp need to operate to pay for itself?



Lamp cost is 3 dollars. Energy savings is 74 watts.


Hours = Lamp cost X 1000 / Watts saved X KWhr


3 X 1,000 / 74 X .15 = 3,000 / 11.1 = 270.27 hours

The lamp will pay for itself in 270.27 hrs of operation

My question is where did this 11.1 number come from? It makes no sense. It appears from nowhere in the equation
 
Hameedulla-Ekhlas

Hameedulla-Ekhlas

Senior Member
Location
AFG
mcclary's electrical said:
This is word for word out of UGLY's 2008




Lamp cost is 3 dollars. Energy savings is 74 watts.


Hours = Lamp cost X 1000 / Watts saved X KWhr


3 X 1,000 / 74 X .15 = 3,000 / 11.1 = 270.27 hours

The lamp will pay for itself in 270.27 hrs of operation

My question is where did this 11.1 number come from? It makes no sense. It appears from nowhere in the equation
Click to expand...


According to your equation in the dominator if you multiply the 74*0.15 it equals to 11.1
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
To clarify my sarcasm, above, it was aimed at Ugly's, not the OP.

To be accurate, the CFL would have to eliminate 270 hours of incandescent use in order to achieve pay off, not just run that long.

In the real world, and I am guilty of this, we tend not to turn the CFL's off as much as the incandescent lamps. For one thing, since they are much cheaper to run the motivation to turn them off when not in use is almost nil. Another issue is the fact that for the first few minutes the lamps are dim. They do not put out their full lumen rating until fully warmed up. Many people don't like having to wait 5 minutes for a decent light so they just leave them on.

To me, making a comparison between incandescent lights and CFLs is like comparing apples to oranges. They don't have the same output no matter what is printed on the box and the users will operate them differently. They also don't work for certain applications. Just think how much fun it would be having to wait until a CFL warms up when it is 0 degrees outside. This is not good for outdoor lights with motion sensors on them.

Any time you need a quick light for a few minutes CFLs are worthless. Have you tried a CFL on your garage door opener yet?
 
StephenSDH

StephenSDH

Senior Member
Location
Allentown, PA
K8MHZ said:
To clarify my sarcasm, above, it was aimed at Ugly's, not the OP.

To be accurate, the CFL would have to eliminate 270 hours of incandescent use in order to achieve pay off, not just run that long.

In the real world, and I am guilty of this, we tend not to turn the CFL's off as much as the incandescent lamps. For one thing, since they are much cheaper to run the motivation to turn them off when not in use is almost nil. Another issue is the fact that for the first few minutes the lamps are dim. They do not put out their full lumen rating until fully warmed up. Many people don't like having to wait 5 minutes for a decent light so they just leave them on.

To me, making a comparison between incandescent lights and CFLs is like comparing apples to oranges. They don't have the same output no matter what is printed on the box and the users will operate them differently. They also don't work for certain applications. Just think how much fun it would be having to wait until a CFL warms up when it is 0 degrees outside. This is not good for outdoor lights with motion sensors on them.

Any time you need a quick light for a few minutes CFLs are worthless. Have you tried a CFL on your garage door opener yet?
Click to expand...

Do you feel better now?:) I always turn of my cfls.
 
L

lakee911

Senior Member
Location
Columbus, OH
K8MHZ said:
Just think how much fun it would be having to wait until a CFL warms up when it is 0 degrees outside. This is not good for outdoor lights with motion sensors on them.

Any time you need a quick light for a few minutes CFLs are worthless. Have you tried a CFL on your garage door opener yet?
Click to expand...

Certain bulbs have no trouble outdoors. I have one on my porch, it's about 75% for about 30-60sec and then it's working just fine.

I do have a CFL in my garage door opener. I think it's great. They last so much longer because they are not affected by the vibration like the incandescents.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
lakee911 said:
Certain bulbs have no trouble outdoors. I have one on my porch, it's about 75% for about 30-60sec and then it's working just fine.

I do have a CFL in my garage door opener. I think it's great. They last so much longer because they are not affected by the vibration like the incandescents.
Click to expand...

Which brands / type are non-problematic when cold?

In my unheated garage in the middle of winter the flourescents, whether conventional or compact, come on with only about 10 percent of their peak outputs. Since I only need them to be on for 20 seconds or so, they don't serve my particular purpose.

Indoors or outdoors, the fact still remains that they do not come on full bright as soon as they are turned on. If you only need the light for a few seconds at a time such as to illuminate walkways, they are a very poor substitute for incandescents.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I've seen CFL's that have been burning for several hours still dim down to pink or purple when the temperature drops.
 
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