| I was told by a lighting designer that a light dimmer can save a lot | of energy. | In fact his claim was that dimming an Incandescent light bulb by 5%, | can save up to 40% of the electricity | consumption.
If this were true, then people would be installing 10000 watt lights and dimming them down to the 1% level.
| I tried to verify this claim but I could not find anything that | matched even near this claim. | In fact, what I read (and makes absolute sense to me) is that dimming | the light, say by 50%, | will only save 40% of the electricity consumption.
The big problem with incandescent lights is that most of the energy going into them comes out in the form of heat, both as convective heat and as infra-red radiation. Light is only a minor side effect of a hot filament. The center wavelength of the radiation is in the infrared range.
When an incandescent light is dimmed, it reduces the temperature of the filament. When the temperature goes down, two things happen. One is that all the radiation level goes down. But the other thing that happens is that the wavelength gets longer and moves deeper into the infrared region. So while the total radiated energy goes down, the proportion of that energy that is in visible wavelengths also goes down. The end result is that the level of visible light reduces faster than the level of wasted radiation.
If you are using light bulbs to provide heat, then, of course, the infrared radiation is not waste.
| Does anyone know (and can justify) what the truth is? | I have some basic EE knowledge and I just cant figure out how the | dimming of 5% can give more | than 2-3% savings, given the loss in heat etc...
Dimming a light definitely reduces the electricity used. Turning off some lights would reduce the electricity used, too. The question you need to answer is which method of reduction would work better for your particular needs.
If you want the softer yellow to orange color effect of a dimmed incandescent light, then dimming can be useful. If you always want to be able to run the light at full brightness for other times when a bright white light is desired, then an adjustable dimmer is probably the way to go.
If you want to simply have less light, and keep it white, then multiple lights on separate switches might be better for you. This is the most efficient way to reduce energy usage by lights. But it can cost more to install because of the extra switches and separate wiring.
If your goal is to have white incandescent light with the least power usage then size the light to exactly what you need and don't bother with dimming.