Now for the bonus extra trickery: Using fewer lightbulbs is better than
using lower wattage ones, as long as you get adequate light distribution.
Higher wattage lightbulbs are slightly more efficient. There is more than
one reason, but one is that thicker filaments can be operated at a higher
temperature (better for radiating visible light as opposed to infrared)
for a given life expectancy.
I wanted to ask about this. Does that mean that a 220VAC lamp is less
efficient than a 120VAC lamp, because the filament has to be much
thinner, and so must be operated at lower temperature?
True, but for among different ways of achieving a given light output
lower wattage (or better still fewer) undimmed bulbs will cost less than
dimmed ones. In most of the USA, the cost of the electricity is so much
more than the cost of buying replacement bulbs that it pays to consider
energy efficiency.
A few bulbs benefit from "soft starting", many and probably most do
not.
I know that I find that the dimmers that have to be turned are *much*
more inconvenient, because instead of just poking it with your hand as
you go by, you have to stop and twist it. When you're just passing thru
a room, it's wasteful of time and patience. And it wears the pot out
faster, because the whole carbon element gets wiped by the wiper each
time it's turned full on. So it will fail sooner, and my guess is the
cost of replacement is much more than the savings of light bulbs you get
from using this instead of push-on type.
There are also dimmers that use a touch plate, and they have a memory
that turns them on at the same setting every time, without any fiddling.
But these are more expensive than the usual cheap dimmer.
And there is the dimmer that's just like a switch, it has the toggle
that can be moved thru its range with the same effect as a regular
switch. Just push up on it quick and it's full on. This would solve
the problem of twisting a regular 'volume control' pot.
[lots of good info snipped - thanks, Don.]