Are my dimmer switches saving electricity?

[Nickcrossland]

Hi,

I have dimmer switches throughout the house (£7.99 Homebase type with a rotary knob), but are they actually saving electricity when they're used? If the light's are on at half brightness, are they using 50% less power?

Sorry if this sounds like a stupid question, but I can't seem to find a straight answer to this.

Thanks, Nick

 

[Diyisfun]

Does using a dimmer switch affect the cost of electricity?




Answer
All a solid-state dimmer does is fire a triac at the correct point in the phase to control the power output. It does not dissipate the excess power like a variable resistor. The triac has about 3/4 of a volt drop across it. With a 120W light bulb this means that the dimmer will dissipate 3/4 of a watt at maximum power, which is negligible. So the dimmer will save energy in the long-run.

The dimmer circuit is actually a power regulator, albiet a choppy one. The lower the setting, the less power the dimmer allows to the bulb. Thus, the overall power consumption is decreased.

How do I know this? I've built light dimmers. Ask me about the ramp voltage.


Answer
The truth is logical. Less light less energy!
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This was a web search

 

[Diyisfun]

This may be better
http://home.howstuffworks.com/dimmer-switch.htm

 

[Nickcrossland]

Thanks, I had done a web search but didn't find these. I'll have a look at that second site.

Nick

 

[tim west]

How do I know this? I've built light dimmers. Ask me about the ramp voltage.

Ah ramp capacitors, unijunction transistors and feedback circuits.
They don't make em like they used to

Old analogue taken over by digital bare bone carcasses controlled by processors.

Oh well I suppose they are a teeny bit more reliable and dont need regular lineups like they used to.

 

[Thermo]

didnt understand a word of that!

So why is it when i turn a light on in a room and turn the dimmer down as low as it will go it is all very gloomy, but if left on a few hours it seems to be as bright as ever. Is it my eyes adjusting to the light levels or do they tend to get brighter over time?

 

[TicklyT]

Probably a bit of both... Your eyes adjust to the gloom, and the component values in the dimmer drift a little bit as they warm up.

A dimmer should save some power, but you will probably have to feed something like 50 Watts of power to a 100 watt incandescent lamp to get the same light output as a 25 watt lamp would give without a dimmer.