Gideon wrote: That is hugely out of proportion with the average homeowner.
I don't know...
My sister in MA did the same thing with her bulbs and had similar results. In response the electric company has changed her meeter three times! This last time they added special tamper-proof turn once bolts to their device... I guess they think, how can it be possible for someone's meter readings to go down by something like 40%, she changed all her bulbs.
So her experience is similar to xerces. It sounds like an improbably amount of electricity you were wasting with your bulbs, but she had similar results.
It makes me think of a wagon wheel chandler my parents have in Arkansas. The chandler uses 10 mini 60 Watt bulbs and most of the light is absorbed by "black" up-lighting reflectors. That chandler is a 600 Watt electric heater running all day and causes higher AC usage in the summer. Changing those out would make a big difference. My sister replaced a number of lights like that. The thing is, modern designers don't usually have one light bulb per room, so each room can draw a lot of power, especially if they installed anything fancy.
I found an LCD monitor for my computer more then halfed my computers power usage (testing with a Kill-a-watt between the wall and power strip). Now I can get my computer, my wifes laptop, and a 100 watt equivalent florescent bulb all on one power strip. So these things made a big difference for me. Though we can no longer heat a room with our computers...
By reducing how much heating you do with Electric, you do have to heat more with another source, gas/oil/wood/solar... But this heat usually costs less then electric so it tends to be a good deal. Also in the summer you have less need for AC because you are running cooler.
And besides changing light bulbs my sister turns off electric appliances not in use, plastics seals windows and runs her heat down to around 60... Makes a big difference.