# Cost of electricity for light dimmer

I have an ordinary room lamp. In the mains lead of the lamp there is a dimmer device. It is continuously variable from very dim to full
strength.
If I set the dimmer to give me a dim light then do I pay less for the electricty than if I used the light bulb at full strength?
Thank for any info. Z.T.
--------
I don't know if it makes any difference but I am in the UK.
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Yes, but you pay more than you would by using a lamp of lower wattage.
For example with a 100 watt bulb, and the dimmer set to deliver 50 watts, the lamp may give out approximately the lumens equivalent to a 25 watt bulb.
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On 26 Oct 2004, someone wrote:

Do you mean that if the dimmer is set at its midpoint to 50 Watts (insted of the full power of 100 Watts) then I pay only for 50 Watts consumption?
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That is true if your dimmer is truly linear. I imagine they really start a bit above zero since they need enough power to give some light out of the filiment. You are saving money with a dimmer light.
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Zarbol Tsar wrote:

Yes, your consumption goes down so your bill goes down (or should). Unfortunately your light output goes down faster than your bill, because light bulbs can't be efficiently dimmed.
--

Tim Wescott
Wescott Design Services
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because
And it should be said that incandescent lights are very inefficient to begin with. The halogen bulbs are the most efficient of the common incandescents, but they can't be dimmed without shortening their life.
Someone needs to point all these questions to the authoritive website for this, Don Klipstein's lighting website. http://members.misty.com/don/light.html

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I don't know where the point would be to get the 50 watts, but the point is that you would be paying for power that would be consumed by a 50 watt bulb but getting only the light you would get from a 25 watt bulb. From the money saving point of view you are ahead to put in a 25 watt bulb (and pay for only 25 watts of power).
A dimmer is for aesthetic purposes. One little advantage is that the bulbs usually last longer when run at low power. Savings there still is tiny compared to the loss of lumens per watt.
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You're wrong both-sorry but that's it.A dimmer is *not* a potentiometer, so there's no energy consumed on it.Usually it has a triac (which is a simple power electronic device, like two thyristors in anti-parallel connection).
-- Dimitris Tzortzakakis,Iraklion Crete,Greece major in electrical engineering-freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr

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Were you replying to a different post than those listed below?
The illumination output of a standard light bulb varies approximately by the square of the applied power. Cut the power in half and you get about one fourth the lumens. That is only approximate and varies somewhat with the type of filament.
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| The illumination output of a standard light bulb varies approximately by the | square of the applied power. Cut the power in half and you get about one | fourth the lumens. That is only approximate and varies somewhat with the | type of filament.
Assuming a constant filament. If you get a lower wattage filament, then you save power, lower cost, and have proportionally less light. But one factor to consider is the human sensitivity and perception of light. And that's non-linear.
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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People fear the resistive losses in potentiometer (or rheostat) type dimmers that have been obsoleted by triac-based ones for decades.
However, a remaining issue is that incandescent lamps operate much less efficiently when dimmed. As a rough general rule, efficiency of a given lightbulb at producing visible light varies roughly with the square of power fed into it. (Roughly, only roughly that is.)
- Don Klipstein ( snipped-for-privacy@misty.com)
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And, as an additional issue, it's generally a bad idea to use a dimmer with quartz-halogen lamps. When dimmed, the bulbs run a good deal cooler, the halogen-sequestering-and-redeposition of the tungsten doesn't work as well, the tungsten tends to plate out on the inside of the tube and dim the bulb, and the bulb lifetime is greatly decreased.
All in all, as others have said, it makes more economic sense to use smaller bulbs at full power rather than dimming a high-wattage bulb.
--
Dave Platt < snipped-for-privacy@radagast.org> AE6EO
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| And, as an additional issue, it's generally a bad idea to use a dimmer | with quartz-halogen lamps. When dimmed, the bulbs run a good deal | cooler, the halogen-sequestering-and-redeposition of the tungsten | doesn't work as well, the tungsten tends to plate out on the inside of | the tube and dim the bulb, and the bulb lifetime is greatly decreased.
And this is a frequent problem with those torchiere floor lamps which usually have a dimmer and a 300 (more than you need most of the time) watt QH bulb. So people dim them, usually. Unfortunately, getting a lower wattage bulb is more expensive, if they can even be found in the same size.
| All in all, as others have said, it makes more economic sense to use | smaller bulbs at full power rather than dimming a high-wattage bulb.
Agreed. Getting variability should be done in the form of turning more or fewer bulbs on. A lamp with 8 small 40 watt QH bulbs and a switch to control how many are on would be nice ... and expensive.
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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wrote:

dimmer
of
decreased.
more
And one oher problem is they're fire starters, but that's a subject for another discussion. My thought would be to replace a larger incandescent blub with a few fluorescents, switched to give a dimming effect. But another possible method, which I see used on the modular furniture 'cubicle' lights, is to use a sleeve over the fluo tube, to dim it by turning the tube. THe tube is partially transparent on one half, so turning it varies the light.
BTW, why would you need eight 30W blubs? You would need a 150W for half as much light, an 80W for quarter, a 30W for 1/10, and some boolean logic in the switching to give other in-between settings. Maybe two 30W, or maybe a 30W and an even lower wattage lamp. But you get the idea. You would only need 3 or 4 lamps, which is much simpler and cheaper than 8 smaller lamps. But I digress from the fluorescent lamps. Just use fluos instead.

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fed into it. (Roughly, only roughly that is.)

Why would that be? With cooler operation, the bulb would last indefinitely. The iodine lets it operate really HOT without suffering the 25 hour lifetime that such operation usually brings.
If there is any darkening with lower power operation, it can be burned off with operation at full power.
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In alt.engineering.electrical Tzortzakakis Dimitrios
| You're wrong both-sorry but that's it.A dimmer is *not* a potentiometer, so | there's no energy consumed on it.Usually it has a triac (which is a simple | power electronic device, like two thyristors in anti-parallel connection).
There is SOME energy consumed there. They do get hot (some get very hot). Certainly less than a potentiometer (unless something has gone wrong), but the consumptions not zero.
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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wrote:

so
simple
connection).
Relatively small. I would expect it would be something like a normal NP junction where the voltage drop is about 0.6 volts. Assume a 50 watt load using about a half ampere current. = about 0.3 watts. Other components in the circuit may have more disappation than that.
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| Relatively small. I would expect it would be something like a normal NP | junction where the voltage drop is about 0.6 volts. Assume a 50 watt load | using about a half ampere current. = about 0.3 watts. Other components in | the circuit may have more disappation than that.
Put a small wattage light in the same kind of enclosure. Experiment until you find the wattage that gives the same temperature rise over a long settling time. Then you'll have an estimate of the waste by the device.
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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someone wrote:

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