Dimmer switches

[wallyboots]

Do you use less electricity if you have a dimmer switch dimmed than you do with it up to full?

[WoWo]

Yes

[markysngc]

depends, old style dimmer switches no, they are just a variable resistor and all that does is convert the electricity thats not going to the bulb into heat.

newer switches will reduce your bill as they work by actually switching the bulb on and off very quickly, as the bulb takes a little time to cool this is not noticable. (not sure on the effect this has on bulb lifespan)

check http://home.howstuffworks.com/dimmer-switch1.h tm for more detailed info

[buildersmate]

Mark
No dimmer produced in the last 20 years does as you are suggesting (acts like a resistor). The switch would get incredibly hot in dissipating the unwanted power.
The answer is as per the first response - Yes.

[markysngc]

i did say old style... and yes a huge amount of heat, in fact enough to be a fire risk which I believe was one of the main reasons the design was changed.

Wallyboots asked about dimmer switches and didn't specify if it was a recent or old one, and a lot of people won't change a dimmer switch for well over 20 years as long as it works in their opinion (i.e. it dims the lights) maybe I should have specified how old old style is.

would be intersted in knowing how the new ones effect bulb life though, if you know, as would of thought that the increased thermal shock on the element would shorten the life quite a lot, especialy if run at a high dim

[musicman1956]

Electricity goes to the bulb at 240volts and always will. The dimmer switch alters the power the bulb uses, from 100 watts at full on down to what ever is selected. The light is only created by the visible heat of the filament being picked up by the eye. The dimmer will get hotter as it is turned down so the wattage passing through will remain constant. You will save no money but the dimmer will now help heat up the room. So instead of paying for light, you are paying for heat. Broad as it is long. Failing that. it's all done by magic.

[buildersmate]

Your answer is incorrect, Musicman.
Have you never heard of thryistors? These are chopping devices that switch the circuit on and off very quickly. Because they are switches they are either open circuit or closed circuit and they consume minimal power themselves - so they don't get hot. The light output from the device being dimmed is dependent on the ratio of the on to off, as driven by the thyristor.

[mibn2cweus]

You do save electricity using a modern dimmer switch but not in proportion to the light you lose. As a rule of thumb dimming 50% reduces electricity used by only 25%. Another way to look at this is that using a lower wattage bulb to achieve the same effective lighting as the dimmer switch will improve savings in electricity. Removing one light bulb from a two bulb fixture doubles the savings gained by using a dimmer to achieve the same effect. The convenience of a dimmer switch along with continuous variability are the main justification for their use.

[wallyboots]

Thanks for your answers. I am much more enlightened (teehee) than I was before. I don't know how old the switch is as I'm in a rented flat but I'm guessing it's from within the last ten years. Basically I've been trying recently to cut down on my energy for the the sake of my wallet and the planet and converted to energy saver bulbs but found that the two dimmer s we have made a god awful noise (I'm assuming this means they're the switching on and off kind of switches) so I've gone to ordinary bulbs again. It's good to know that I might save a bit by dimming a little but I guess I'll just have to live with my bills like they are. Thanks again.

[Cakeboy]

Energy saving bulbs are not designed to be used with dimmer switches. All the bulbs I've bought have expressly said "Do not use in conjunction with a dimmer switch"

[webdude]

New technology now enables some LE bulbs to be used in conjunction with standard dimmer units.

http://www.nigelsecostore.com/acatalog/Dimmabl e_.html

and also
http://www.low-energy-lighting.com/bulbs.htm