The cost of turning on a fluorescent light?

[Mr__Bill]

At some time in the dark past I learned that it cost as much to ignite a fluorescent light as to keep it lit for 20 minutes. This may date back to the ones with the replaceable starter or it may not have been true at all.

I was wondering if anyone who has the gizmo for recording how much amp draw a device uses has ever tried it on fluorescent lights? The lights in our garage/shop space are two tube T12 40W and I tend to leave them on if I am going in and out, thinking that I am saving electricity by not turning them on so often. So I got to thinking, do they really take that much electricity? Do the newer ones with the skinny tubes start up with even less of a draw?

Just thought I would ask in case someone has tried it and knows.

Bill
winter is coming! Except for Rod Kirby who will have to suffer through another summer.

[dbhost]

That is a GOOD question... I am going to have to pony up for new fixtures as the T12 bulbs are about to be a thing of the past...

[Tom Slick]

With modern ballasts I don't think startup is as much of an issue as it used to be.
Keep in mind that a fixture with 4 32w bulbs costs about $0.02 per hour to operate at $0.12/kwh. If your shop has 10 32w bulbs, They'll burn for 26 hours before using $1.00 worth of electricity.
If your example is true those 10 bulbs cost 1 penny to turn on, so that first hour costs $0.05, then $0.04 for every hour after that.

The bigger issue in my mind is the reduction of bulb life from each cycle.

[cabinetman]

I don't know what it costs, but we have a 4', 4 lamp (F40-T12) flourescent in our kitchen that hasn't been turned off in 10 years. I think I've replaced one of the lamps...and that's it.

.

[BobSch]

Here's what the Lighting Design Lab has to say on the subject.

Should I Turn Off Fluorescent Lighting When Leaving A Room?
Short Answer: Turn them off if you will be gone for more than about 15-20 minutes

http://lightingdesignlab.com/article...luorescent.htm

[chopnhack]

Mike, why?

[LCHIEN]

this article by the US Govt:
http://www.energysavers.gov/your_hom.../mytopic=12280

sounds pretty truthful to me.

Basically is says that the turn on surge is short and excess power consumed is only equal to a few seconds of lighting. But when you factor the wear and tear on the lamps reducing life then you would be better leaving the lights on for absences of around 15 minutes or less.

[cabinetman]

Mike, why?

Our kitchen is in the middle of our house, with an easterly window exposure. It's not particularly bright during the day with the light off. At night it's dark as all get out. So, LOML wants the light on all the time, as a night light. During the day she doesn't want to have to turn on a light, especially if her hands are full of groceries.

Besides, all our animals like the kitchen all bright and cheery.

.

[LCHIEN]

Our kitchen is in the middle of our house, with an easterly window exposure. It's not particularly bright during the day with the light off. At night it's dark as all get out. So, LOML wants the light on all the time, as a night light. During the day she doesn't want to have to turn on a light, especially if her hands are full of groceries.

Besides, all our animals like the kitchen all bright and cheery.

.

mmmm, makes all the veggies look nice and green and vibrant.

[cabinetman]

mmmm, makes all the veggies look nice and green and vibrant.

Not for them...we keep them in the refrigerator...it has its own light.

.

[woodturner]

Basically is says that the turn on surge is short and excess power consumed is only equal to a few seconds of lighting. But when you factor the wear and tear on the lamps reducing life then you would be better leaving the lights on for absences of around 15 minutes or less.

Good points. The "leave them on for 15 minutes to save energy" urban legend got started based on flawed "research" by a consumer magazine, and was never really accurate. The wear and tear issue is a real consideration, but it's more significant for incandescent lights. Incandescent lights typically fail when first turned on - the temperature change as the filament heats causes the failure. If you reduce the number of on/off cycles, the bulbs last longer.

[cabinetman]

Some words have multiple meanings, like the word 'bulb'. It's common use is a botanical term.
http://en.wikipedia.org/wiki/Bulb

When I started out, my first products were lighting fixtures, and the term was 'lamp', not 'bulb', which referred to both incandescent and fluorescent. Some today still refer to 'lamps' as 'bulbs'. Interestingly enough, other uses for the word 'bulb'.
http://en.wikipedia.org/wiki/Bulb_%28disambiguation%29
http://dictionary.reference.com/browse/bulb
http://www.answers.com/topic/bulb

.

[LCHIEN]

Good points. The "leave them on for 15 minutes to save energy" urban legend got started based on flawed "research" by a consumer magazine, and was never really accurate. The wear and tear issue is a real consideration, but it's more significant for incandescent lights. Incandescent lights typically fail when first turned on - the temperature change as the filament heats causes the failure. If you reduce the number of on/off cycles, the bulbs last longer.

actually, read the link i posted.

They say that with fluorescent bulbs the equipment (bulbs plus ballasts) is relatively costly so you want to avoid on-off cycles that reduce life of the equipment. Hence 15 minutes.

They say that for incandescents, the inrush is high but short, too, BUT you should turn them off for even a short absence of under say, a minute. The low power efficiency wastes more power per minute and on top of that, the equipment (filament bulbs costing around a quarter each - my observation) is so cheap its not worth saving bulb life in exchange for even a little wasted power.