Does dimming a light switch save electricity?

Answer 1

The newer style dimmer switches do save some electricity when they are dimmed. If you really want to save electricity, replace your old incandescent bulbs with the new compact flourescent light bulbs.

It has been estimated that if every household in the US would replace just ONE bulb with the compact flourescent, we could close down two power plants in the US.

Let's say you replace ten 60-watt bulbs with ten 15-watt CFL bulbs. That saves you 45 watts per bulb, or 450 watts for all ten. Let's say all your lights were on for six hours a day, five days a week. That's thirty hours a week, or about 1500 hours a year. So your 450 watts savings times 1500 hours a year = 675,00 watt-hours. Divide by 1000 and you have 675 kilowatt-hours (kWh). If you're paying 15¢ per kilowatt-hour, then you'll save $101.25 a year.

There is a down side to these bulbs. They do take a few minutes to get up to full brightness. I have replaced all my lights in my house, and they work fine. My electric bill did go down.
A huge advantage is these bulbs last a long, long time.

Answer 2

Yes they do save electricity.

The answerers who talk about the dimmer switch putting a resistor in the circuit are wrong. They do not understand how a dimmer switch works. Very simply they work as follows:

Dimmer switches use a thing called a thyristor to 'chop' the incoming electrical sine wave into "chunks" separated by short periods of time when there is no current.

These chunks of current are fed to the light bulb's filament and make it glow. During the non-chunk time the filament cools a bit and so goes dim.

Because these on-off cycles happen so fast the thermal lag in the filament means that the 'bright' and 'dim' cycles are so rapid you cannot notice them. But the average light output is less than it would be if the thing was powered all the time.

The resistor that is built in to dimmer switches only allows you to vary the relative lengths of the on-off cycles. It does not pass any current directly to the bulb.

During the "off" time between chunks the bulb is drawing no current and the electronics in the switch draw hardly anything, hence you save electricity.

Warning: you cannot use conventional dimmer switches with fluorescent lamps, including 'energy savers' as these are just modified fluorescent tubes.

Answer 3

Well thanks for the feedback so far all. I have low voltage fittings which use MR16 bulbs and I purchased transformers which are dimmable. However I may have got some of the light switch's wrong. I thought all you do is add up the total Watt for the number of lights you have and then get a dimmer switch which has a Watt rating above that. e.g. For 4 x 50 Watt I have used 250 Watt dimmer modules. And for 6 x 50 Watt I have use a 400 Watt dimmer module. They do hum I have noticed however someone said to me that when you dim the lights the difference in power is simply used up by the dimmer module hence why it gets hot! I will look at Toolstation ( who I have used loads during this project) but I didn't realise that this was so complecated at all. I thought dimming the lights would save electricity plain and simple. But things never appear to be as simple as you may expect :) Thanks so far all!

Answer 4

The usual selection of incorrect answers. YES! A dimmer switch does save electricity,At 25% dimming, energy is reduced by about 20%. At 50%, 40%, and at 75% dimming, 60% energy is saved. The other good thing is that lamp life is extended by about 4, 50 and up to 70 times. The dimmer is an electronic circuit not a resistance, and dims the lamp by rapidly switching the supply on and off, usually with a Triac. Good quality dimmer switches usually also have a 'soft start' circuit which reduces the surge at switch on to prevent lamp failure.

ADDED - Re the answers below, The best dimmer switches do not use cheap thyristors, (which usually buzz at about mid-setting), but Triacs. Eg. Lutron, which are virtually silent at all settings

Answer 5

Hi smiff. Depending on the type and efficiency of the dimmer some saving can be made. However the saving is likely to be less than the dimmer cost you. It is marginal at best, The reason being that lamp efficiency diminishes rapidly as the dimming takes place. Lamps are designed to be run at full voltage. Only use a dimmer if you want to decrease the lighting. Otherwise smaller bulbs and or the new energy saving types, which save about 90% of the electrciity used as apposed to the old incandescent types.
Regards
Bill

Answer 6

As domestic household power supplies are AC (alternating current) this means its not possible to use a resistance method of controlling the voltage. Therefore, as some of the answers above say, it's controlled by rapidly switching the bulb on and off, so one would assume that this would conserve a very small ammount of electricity.

Answer 7

Yes but overall it will be negligible. Of all the electrical systems in your house your lights draw the least amount of current .

Incidentally dimmer switches use thyristors to control light intensity by blocking part of the alternating current (for an adjustable time delay), thereby allowing only part of the current through the dimmer and reducing the power input to the lamp..

Answer 8

Dimming a light will not save electricity. The voltage, current, and wattage does not decrease. When the light is dimming what it is actually doing is turning on and off repeatedly at different rates depending on how much it is dimmed. It is so fast that you do not notice its 'off' stage. This is the "New and improved way" from the old resistor method.

Answer 9

Yes. Dimming the light increases the resistance in the circuit (meaning less current is flowing). While the dimmer will cause some heat to be generated, the overall current will be less. Less current means fewer watt-hours will be measured by your meter.

If you want to save more electricity, use flourescent bulbs, but CHANGE OUT the dimmer to a standard light switch first unless you want to buy flourescent bulbs specifically made for dimmer switches. (They are more expensive.)

Answer 10

Yes, just dim it at least 75% so that you make up for the resistive heating loss from the dimmer.