Start vs. Run

[kit]

I've heard that the amount of electricity required to start a standard fluorescent tube is about the same as letting the tube operate for several hours.

Is this true of CFLs or LEDs as well? If so, is it advisable to turn them on-and-off in the time that you need them, or just leave them on the whole time?

[dave]

Kit, see the following. The "bottom line" is contained in the third reference, below, at energy.gov. It contains this:

CFL Lighting

Since they are already very efficient, the cost effectiveness of turning CFLs off to conserve energy is a bit more complicated. A general rule-of-thumb is this:

If you will be out of a room for 15 minutes or less, leave it on.
If you will be out of a room for more than 15 minutes, turn it off.

The operating life of CFLs is more affected by the number of times they are switched on and off. You can generally extend the life of a CFL bulb more by switching it on and off less frequently than if you simply use it less.

It is a popularly held belief that CFLs use a lot of energy to get started and it is better not to turn them off for short periods. The amount of energy varies between manufacturers and models—however, ENERGY STAR© rated bulbs are required to endure rapid cycling for five-minute intervals to ensure that they can hold up to frequent switching.

Scientific American - Does Turning Fluorescent Lights Off Use More Energy Than Leaving Them On?
www.scientificamerican.com/article/turn-fluorescent-lights-off-when-you-leave-room/

Mythbusters Test the Effects of Turning off the Lights
www.vanderbilt.edu/sustainvu/2006/12/the-discovery-channels-mythbusters-test-the-effects-of-turning-off-the-lights

When to Turn Off Your Lights
energy.gov/energysaver/when-turn-your-lights

Pros and Cons of CFLs
michaelbluejay.com/electricity/cfl.html


CFLs: More Hype than Value
www.richsoil.com/CFL-fluorescent-light-bulbs.jsp

[kit]

Thanks Dave for providing all this information. After digesting much of it I'm more aware of the best way to use the bulbs I have.

I mostly use CFLs and shy away from tungsten bulbs for 3 reasons:
1. Cost to run
2. Heat generation
3. (important to a photographer) Color temperature

I only use 1 tungsten bulb and that's a 200 watt bulb on a dimmer that hangs over my dining room table. I can control the amount of light (which is also proportional to cost and heat) for bright when I'm doing a project on the table, or turn it down to soft for that warm glowing atmosphere when I'm schmoozing with a pretty lady over a fantastic dinner (only kidding about the lady [mostly] but some of the dinners are indeed fantastic).

There's only one LED tube in my apartment and that's in my kitchen. The bulb is purchased and replaced by the property owner so I don't worry about the cost. I like it for 3 reasons:
1. It's 'instant on'
2. It's very bright
3. Its color temperature is close to daylight where colors render properly

So now, thanks to your research, I'm more aware of how often to turn them on or off as well.

[clarencebunsen]

In order to maintain my know it all status, I'd like to point out that in an industrial setting the calculation my be different than in a residential setting. In most places industrial customers pay a "demand" rate which charges not just for the number of kilowatt-hours used but also for the peak usage. The momentary surge of switching on a bank of 8' fluorescent tubes can drive your rate up for an entire month. Throw in start up of large electric motors which are and inductive load with the tubes which are a capacitive load and I was never able to determine if there was an optimum start up strategy.

[dave]

CB, I'd forgotten about that, and didn't know the penalty for an instant of demand was so severe. ("The momentary surge of switching on a bank of 8' fluorescent tubes can drive your rate up for an entire month.")

I wonder if such nonsense will evaporate over time as has (I'd say) the telephone company's old relationship held between toll and miles distance. Cell phone rates are based more on usage time, at least with the "call anywhere" plan we have. Usage time billing makes more sense than "distance," the latter of which in reality does not exist in measurable ways on packet switching networks.

[clarencebunsen]

True for telephone transmission not so much for power. Transmission losses are still linear with distance. The infrastructure must be in place to meet peak demand. For me demand pricing meant that I paid a demand charge based on the half hour in the month in the month with the largest draw. My charge per kilowatt-hour was lower than a residential rate but I typically paid in excess of $10k per month with half of that being the demand charge. It was more in the air conditioning months.

Industrial usage is really different from residential usage. Waaay back in the day there was a malting plant outside of Jamestown ND. Probably still there but I haven't been back in a long time. Malting plants take grain, sprout it in warm water, dry it and process it for use in making beer, malted milk and such. As such things go it wasn't big in the eyes of the world. However it was a bigger load than all of the rest of Jamestown combined: 13,000 people, stores restaurants, businesses, schools and a small college. If a homeowner upgraded his electrical entrance from 60 amp to 100 amp it was no big deal. When the malting plant added another production line it was a huge deal. It took my father more than a year to get the infrastructure in place. As I recall the lead time for just one of the transformers was 12 months.

[dave]

Yes, power versus telephone transmission noted. Again, hadn't thought of that. Your engineer's mind is still sharp.