[Ether]

Here's my source for the figures I chose: http://www.amazon.com/WATTS-LIGHT-FR.../dp/B000ST9AMM

I didn't see a lumen rating anywhere on that site. Do you own any of these? What's the lumen rating ?

The prices I chose were listed on the Department of Energy website: http://www.eia.doe.gov/electricity/epm/table5_6_b.html

Yes. My point was, the analysis depends heavily on the electric rates in your local area.

But in the summer, your air conditioning has to fight the heat generated by incandescent bulbs.

Of course. But in summer you use the lights a whole lot less, and most days (in colder climates) you can leave the windows open and let the breeze cool the room.

I've seen prior calculations (can't seem to find the link now) that show from a heating/cooling issue between incandescent and CFL bulbs is a wash for most of the US.

The operative phrase above is highlighted. In my post, I specifically mentioned colder climates.

I chose eight hours per day as an average value for most lights in "busy" areas of a house/apartment.

Thanks for clarifying that.

I was considering solving these equations as a function of the hours per day of operation, but then I realized that the only difference this has is to shrink or widen the time bands. The ratio of break even point relative to the entire life of the bulb remains the same.

But "break even point relative to the entire life of the bulb" is not the metric you care about. To illustrate this point by (unrealistic) exaggeration, imagine you used each bulb only 2 minutes per day. The break-even point would be too far out into the future to even make a useful analysis.