Just got our first full month electric bill since switching out our most frequently used light bulbs with CFLs (6 bulbs).

Along with other conservation measures, it looks like we had about a 15% savings compared to the same period last year, which for us works out to about $26 for a 30 day billing period at the current rates.

So basically, the CFLs have already paid for themselves (which doesn't seem possible, but there you go). Our savings may be higher because we work mostly from home so we are here 7X24 so our lights are on longer. Your mileage may vary.

It should also be noted that the average daily high temperature for June 2007 was about 2 degrees higher (88.5) as compared to June 2006 (86.6), so it's likely we ran the AC a little more this year than last.