does a dimmer switch (a rheostat) on a light reduce power consumption?

Question

the question being, will installing a dimmer switch reduce my electric bill?

Answer 1

The term rheostat, tends to be an older expression that dates back to the days of using "windings" and a variable "wiper" to provide a variable resistance model between the supply and load, (light). With such a resistive device, the power consumption is actually increased slightly due to the additional component's presence in the circuit, but more importantly whatever power is not going to the bulb, is generated as "heat" at the windings.

In more recent years, we have moved to solid state devices which control the on/off time per each cycle of the AC current or a cyclic off time x times per second on DC current, but either way, the net result is a reduction of power consumption equal to the change in power factor, less a very slight amount of heat generated at the solid state device.

So yes, a solid state "dimmer" of recent and typical design can reduce the amount of overall wattage consumed for a given amount of light produced.

Keep in mind if you install a dimmer on the light over the stairwell and then fall down the stairs for not seeing the way, the medical bills may exceed the annual net savings from the dimmer. ;-)

Answer 2

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does a dimmer switch (a rheostat) on a light reduce power consumption?

Answer 3

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The correct answer is yes, provided you are comparing it to operating the light at full intensity. A dimmer reduces the power output of the light, and therefore allows you to use less power when you don't want as much light. Many ill-informed people will claim that dimmers don't actually save power consumption because it converts it all to heat in its resistive windings. This is a myth, and they are not engineers. At least...they shouldn't be. The truth is that the heat generated by a rheostat is a fraction of the amount of energy actually attenuated. The heat is generated simply due to the fact that real rheostats are imperfect devices, and suffer some real-world energy loss. Think about it. You have a light bulb that's burning well over 200 Degrees Farenheit. If you were to really put a "dimmer" device on that that changes all of its power to heat...your "dimmer" would get blazing hot wouldn't it? Does a Rheostat get that hot? Nope. Not even old-style dimmers. New solid state dimmers are even more efficient, and incur even less power loss. A Rheostat reduces the current flow across the appliance, reducing the power consumed by the system, period. Other folks will point out that if you run the light with the dimmer but at full blast, that it will use *more* power, bcs of the addional loss in the system. They have a point, but fail to see the larger picture. The energy loss of incorporating a dimmer device will indeed consume more power at full blast than one without a dimmer device, but will give you the ability to save significantly more power in allowing easy dimming. The alternative is moronically having to replace the high-wattage bulb with a lower wattage bulb every time you want to save power, to save the milliwatts of power loss you'd have incurred by incorporating a dimmer. And of course, I woud add that it would be vastly more effective to use a more efficient light source to begin with as a power-saving measure. Incandescent lights produce more than 90% heat, and only about 10% light. Flourescent lights, on the other hand produce much less wasted energy in the production of its light.

Answer 4

Rheostat Dimmer

Answer 5

Yes, using a modern dimmer will reduce power used by your lights by rapidly cycling them on and off, and save you some money, but unless you consider also increasing the effective light output of the bulb you are using at a lower wattage input (e.g., by replacing your incandescent bulbs with a CFL or LED), simply adding a dimmer and dropping the setting will simply leave you in the dark.

Answer 6

Rheostat Switch

Answer 7

A rheostat is an old fashioned dimmer. It is not used nowadays. It does not reduce electricity consumption, it turns part into heat, and the rest goes to the lightbulb.
The kind of dimmer that is used in modern households is called a SCR - Silicon Controlled Rectifier, and it does save electricity, it works like a switch, turning the light on and off several hundred times per second. The more time the light is off, the darker it looks, as your eyes can't see the on-off switching, it happens too fast.

Answer 8

THe answer is yes but not for the reason you are saying. In old days a rheostat (variable resistor) was really in the dimmer and whatever power wasn't in the light was being wasted in the rheostat. That meant you did not save any energy. Nowadays they use a triac (a pair of SCRs arranged for use on AC) which turns the power to the lamp on and off. The brighter you want the lamp to be the more times per second you tell it to give power to the lamp. When it is not giving power to the lamp than no energy is being used. So the modern answer is yes you can save with dimming lights because they are on for less total time and not using power while off.

Answer 9

I would say so, but if your mayor concern is your energy bill, I would try switching to CFL (compact fluorescent lamps), almost the same quality and quantity of light, at a fraction of the power consumption.

Answer 10

As a general rule any time you lower wattage you lower power consumption. If all of your lights were aided by dimmers you might notice a slight difference in the bill, but not that much.

Answer 11

Installing a dimmer switch will not lower your bill enough to notice any difference. You should change all the bulbs in your house to the new fluorescent type. Over a period of time you will notice a difference. These type bulbs are expensive up front but over the long term they will help. They are also supposed to last a lot longer than regular incandescent bulbs.