Matthew's Journal

Assuming the light bulbs are conventional incandescent tungsten-filament affairs, it makes no difference how gradually you turn them off, but it certainly prolongs bulb life to dim them up rather than turn them on abruptly.

If you need convincing, think about lights that don't have dimmer switches, and note that they burn out when being switched on much more often than they burn out in use.

Personally, I favour the kind of dimmer that one rotates fully anticlockwise to turn off, for precisely this reason.

As for energy saving, I doubt it makes much difference, except of course that light bulbs themselves cost energy to make, and you'll save some of that if you make them last longer. Arguably you save a little energy if you turn the light on gradually, simply because it's on fully for marginally less time. But then you counteract the saving if you turn it off gradually. (-8

What is inefficient, though, is leaving the lights dimmed. Incandescent bulbs aren't terribly efficient at the best of times, of course, but when dimmed an even greater proportion of the energy they consume is emitted as heat. If you find yourselves always keeping the lights dimmed, change to lower-wattage bulbs.