Cost-effective LED light bulb

Home Depot now has an LED light bulb that has roughly the same lifetime cost as CFL. It's here:
A19 8.6-Watt (40W) Warm White (3000K) LED Light Bulb-ECS 19 WW 120 at The Home Depot

It's $10 for a 40-watt-equivalent bulb. Comparing the lumens, watts, lifetime, and price to the 40W-equivalent CFLs at Home Depot, it's a little dimmer and a little less efficient (lumens/watt) than the CFL. It's also apparently quite directional compared to a CFL.

That said, if you can ignore the fact that it's dimmer, it has a lower lifetime cost (using $0.12/KWH). If you adjust for the dimness, it costs about 9% more (per lifetime lumen-hour) than the 40-w-e CFLs on the same site. I'd call that more-or-less break even.

Interestingly, this is the first product I've seen on the Home Depot website that says "limit 10 per order". So it must be a pretty good deal, or something.

To put it in perspective, last LED I bought was 15W, for $10. This is now 40W, for $10.

Both this LED and comparison CFL are substantially less efficient than (e.g.) linear fluorescent tubes. But if you need a bulb in this package, it seems like you've now got an LED bulb that, at rated lifetime, is as cheap as CFL (at $0.12/KWH).

As an afterthought: The rated lifetimes are getting so extreme that it may not be realistic to calculate the average cost based on the lifetime.

These are rated at 50,000 hours. At 8 hours per day, that's more than 17 years. At 2 hours per day, that's ~68 years. I'd say the market for used lightbulbs is non-existent, and likely to remain that way. So it's a fair guess that much of the rated life of these bulbs will go unused.

Unless you're planning to pass them down to your children, you'll need to substitute the lesser of the bulb's rated lifetime, or your own rated lifetime, in your own cost-effectiveness calculation.