Switching to Flourescent Light Bulbs & Savings Calculations

I just finished replacing all of my 60-watt regular incandescent light bulbs in my place with the equivalent 11-watt fluorescent ones. I had been waiting for each to burn out one-by-one, but after finding a bunch on sale at Ikea I just decided to do them all. After crunching some numbers, it seems like that would be the best decision anyways. Here are my calculations:

10 bulbs x ~4 hours a day x 1 year = 14,600 hours of lighting.

Cost of electricity:
60 watts x 14,600 = 876 kW-hr vs. 11 watts x 14,600 = 161 kW-hr.
Savings: 515 kW-hr x 0.083 cents/kW-hr (taken from recent bill) = $43/year.

Cost of bulbs:
At a lifespan of 1,000 hours for regular bulbs, I’ll need 14.6 new bulbs/year x $0.50 per bulb = $7.30/year
At a lifespan of 10,000 hours for fluorescents, I’ll need 1.46 bulbs/year x $2.50 per bulb = $3.65/year (exactly half, whoa.)
Savings: $3.65/year

Cost of 10 new bulbs: $25. Total savings from switching: ~$47/year.

Not too shabby, I’ll make back my investment in little over half a year. I’m also pretty impressed with the bulbs. My older fluorescents are the spiral-type, and sometimes take a couple seconds to reach full brightness. These new ones are “linear” and more compact, and light up almost instantaneously. Too bad this is basically the extent of my handy-man capabilities.