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Dimmer/Toggle Switch

Discussion in 'Electrical Engineering' started by Kissi Asiedu, Dec 31, 2005.

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  1. Kissi Asiedu

    Kissi Asiedu Guest

    Would the replacement of regular toggle switch with a dimmer have any effect
    on energy savings? What I want to know is that, if I dimmed a 40W light bulb
    for about 3hrs compared to a switch that stays on for the same period of
    time, would the electric bill be the same?
  2. Rich256

    Rich256 Guest

    Depending on your rates, it might cost you a penny to run the 40W bulb for
    three hours. Put in a dimmer and you might save 1/4 of that. You might
    save 10 cents a month.
  3. EpsilonRho

    EpsilonRho Guest

    A common question is whether dimmers actually cut electrical use.
    Modern ones do! Very old resistance dimmers didn't (some folks still
    call dimmers "reostats".)

    Sorry, but this is not true. Reostats do reduce total power consumption,
    although not efficiently.
    Example: Bulb = 120 W @ 120V; I=1A: R=120Ohm
    Add 120 ohm resistor in series (set with the reostat):
    Total power: V^2/Rtot = 120x120/240= 60W! The bulb uses 30W and the reostat
    but the total power is half of the lamp used without reostat.
    You could do the generic algebric calculation and find a hyperbolic relation
    between total power
    (y-axis) and total resistance (x-axis).
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