Power consumption of fluorescent lights

where I work the justification not to switch on/off for a short period of time was calculated based on the life expectancy difference on the bulbs, as the frequency of switching is higher the life is shorter and the maintenance cost is higher.

Turning them on consume not so much power really. If you don't belive me, look at the way that other light vary when you turn on a big motor and when you turn on a bunch of lights that doesn't happend. Anyway, if turning them on would consume ten times the average current and usually it takes few seconds to turn on, it would be the same (from an energy cost viewpoint) than the same light turned on less than a minute.

Anyway, the life of the fluorescent lights that you turn on and off might be shorter (how much is a really good question). THIS is the issue when it comes to the money. I suggest you that you keep a recordbook and to turn on and off just a half of the lights (for a clean startpoint, all lights must be brand new). If you see some difference between lifetimes of fluorescent lights, register how much does it cost and how much did you save in power. Power nowadays isn't that expensive (I think it would be cost-better if you let them on), but maybe you can get some answer that might be impressive.

You must try it (scientific experiment, wow!)

The concept of "saving" energy by leaving the lights on was actually tested by Discovery Channels Myth Busters. They tested several different types of bulbs and measured the energy it took to turn them on vs the energy they consumed staying on. In all tested bulbs, standard, fluorescent and even the energy saving bulbs, they found that personnel could save energy by leaving the light on, if they where on for less than 45 seconds at best! Over 45 seconds all lights used more energy staying on vs. turning them off and then on when they are needed. Even with the wear and replacement of bulbs or tubes there where still savings by TURNING THE LIGHT OFF.

Just to make sure I did my own little test around the house. Over a 3 month period we left a fluorescent tube on over a month, having recorded a month of standard use of the energy used. The third month we turned the tube off when we didn't need it. The difference was pretty clear and showed an immediate saving of energy.

I think if more companies would turn the light off, computer monitors off standby and turn them off completely their energy cost would dwindle.

Try it out at your facility, record a month of energy consumption and follow that up with a month of "lights out". Let me know what you find out. You can email me at carty_1997@yahoo.com

Carty

You are right. But we are forgetting one basic thing that this depends on where lights are installed? If it is air conditioned atmospere, it is advisable to switch off light to reduce load on air conditioner. If, it is not, I agree with you. Today's development is toward voltage reduction during break time or idle period. As florescent fixture power consumption reduce with reduction in voltage, this method may works best. This should be done after through technical discussion with lumineries manufacurers.

It is a similar story for incandescent Lights. If they draw 10 times the power for the first second, then the break-even point would be 10 seconds. There is an associated stress with turning lights on and off, but there is also evaporation of the filament happening all the while the light is on. This is also true of fluorescent lamps. The life of the light is probably more influenced by the filament evaporation than by the stress of turning on and off.

Quartz-Halogen lights probably would suffer if they were being turned on and off in cycles somewhat under a minute (guessing on the time). This is because they rely on the high temperature of the internal gases to return the evaporating tungsten back onto the filament. If they spend a significant time below operating temperature, more tungsten would evaporate. Still, if not in use for over a minute (say), turn them off.

Therefore, turning lights off when not in use is definitely a net savings of energy, and probably prolongs the life of the lamp. (perhaps a more significant issue nowadays is the potential impact of global warming that could be significantly reduced by getting in the habit of turning off unused lights.)

Tube life of a flourescent is definitely a factor of starting stress. Yes, the filament evaporation happens, but I have a 18 inch, 30W flourescent with magnetic ballast, in my kitchen that stays on 24/7. The last tube went 8 years 24/7 before it failed (That's more than 70,000 hours to you and me). The kitchen faces north in a wooded lot so it is somewhat dark during the day, and leaving the light on at night provides enough lumination throughout the downstairs for safety reasons for those who get up during the night. Obviously, there is some cross-over point considering the cost of energy (leaving the lights on for an hour) versus the total cost of replacing the bulbs (material and labor). I'll bet a Sylvania engineer can tell you how many starts a typical bulb is good for. With that knowledge you can calculate the costs of doubling your starts versus the cost of electricity for an hour a day.

Honestly, I don't have much to add on this, but thought I would.

During the first 100 milliseconds to perhaps 1+ second that current/power surge occurs for lighting the lamp(s). I don't think this is the real issue.

Over the years I've have an observation where flourescent lamps tend to have a shorter life when turned off incrementally during each day. So do their buddies, the ballast fixture (not really cheap or a snap to replace, like maybe the lamp(s)), both residential and commercial (plant) environments. Otherwise said, leaving them on only when needed for residential is good; and for commercial: during the hours of 8-5 or as applicable (8-5 or during biz hours).

That's my vote and opinion. ps: I don't work for the power company.

The rule of thumb for fluorescent lights is that if you can shut them off for 20 minutes or more the energy savings will more than compensate for the increased maintenance costs of tube and ballast replacement -- that's taking into account both manpower and material costs. The additional amount of energy consumed during start-up is insignificant. You save that amount in the first few seconds the lights are off.

A light that is switched off draws no power from the supply.

Some supplies, particularly domestic, are metered on the actual energy consumed and one pays by the unit of kWh used. Commercial and industrial supplies are sometimes charged on the basis of peak demand. These different ways of charging are called tariffs, and are set by the local electricity supplier. Whether one pays any more depends on the charging tariff used and the pattern of use.

Sometimes, significant savings in cash can be made without altering the demand simply by changing tariff. Sometimes significant savings can be made by altering the pattern of demand within the same tariff. In all cases, local conditions will dictate the appropriate courses of action.

Whether one uses any more or less energy is also becoming a significant matter of personal conscience in these environmentally-sensitive days.

this doesn't answer the Q.