Electrical - residential lighting question

Dimmers reduce power to the lighting source or bulb, so they save energy and can extend bulb life. Incandescent and halogen bulbs last up to 20 times longer when used with a dimmer, increasing the money saved.LED bulbs run cooler when dimmed which can also extend bulb life.

What???

There will be some loss, but I've never seen one act like a voltage divider.

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On most dimmers, no. There is less power making it to the bulb, but the dimmer does that by turning excess power into heat. You'll notice that dimmers are typically warm to the touch, which is the excess emerg being burned off.

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You can also hear a buzzing/humming sound coming from most residential dimmers. Not always, but if you turn the one in my kitchen below halfway it buzzes and gets warm.

Uhhhh yes.


Also, you will use less gas in your car if you hold the accelerator halfway down as compared to flooring it.

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On most dimmers, no

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This is wrong depending on what you mean exactly. Older dimmers were typically potentiometers, essentially variable resistors.

There was some inefficiencies so 50% dimming didn't equal exactly 50% reduction in wattage but it was pretty close.

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but the dimmer does that by turning excess power into heat

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Well, yes but that is only because the resistor heats up but the filament in the bulb heats up less than it did before and all of that heat is actually wasted energy either way.

There are two ways to reduce power usage. Power (p) = Voltage(V) * Current(I)
SO you reduce power by either reducing the voltage or the current in the loop

For potentiometer type dimmers:
I= V/Resistance(R)
So P = V*(V/R) or P = V^2 /R

As R increases, P decreases

For more modern dimmers that clip the sine wave you are reducing V.

Also, with LEDs you have much less energy lost to heat provided the bulb had good quality electronics.