Joseph Meehan wrote:

... if you had 10 lamps in the room you could dim them all 50% or
turn half of them off and save a little more energy.

Wikipedia says the power used and light output of an incandescent bulb are
proportional to V^1.6 and V^3.4, so light is proportional to V^(3.4/1.6)
= P^2.125, no? Turning half off makes half the light with half the power,
but dimming all to 50% power only makes 0.5^2.1225, ie 23% of the light.

Making 50% of the light requires dimming them all to 0.5^(1/2.125), ie
72% of the original power. That's a lot vs a little more energy, IMO.

Then again, CFs are 4X more efficient, and some dimmable CFs have
a light output that's directly proportional to power :-)

Nick