In recent years we have switched heavily to the various "energy-efficient" light bulbs - in some cases, with certain sizes/wattages of bulbs, they are even mandated by law now.
The advantage of these new kinds of bulbs - CFLs and more recently LEDs - is that they use far less electricity than the old incandescent types that ol' Tom Edison knew and loved. That seems to be true, and that's a good thing for the planet.
But as with most sorts of energy use, cost is also a key factor. Coal, for example, is dirty but cheap in the distorted energy market that was created for it.
In the case of light bulbs, we were told that the higher cost of the newer bulbs would be OK because of their much longer lives. That part, though, seems still to be untrue.
We put a lot of CFLs in, 6 or 7 years ago and they proved to be quite a disappointment. (See "Ecodumb.") But those were just new versions of the old flickery fluorescent tubes that nobody liked anyway. Fortunately, they didn't last worth a damn so I was undeterred.
My next step was "up" to the "much more reliable" LEDs. Sadly, though, any insurance company trying to insure these new bulbs would quickly go broke. The six CFLs that failed so miserably in "Ecodumb" were duly replaced about two years ago with new LEDs. They look like this:

The detailed text on the [overpackaged] box makes the claim that these bulbs have an average life of 22.8 years when used about 3 hours per day. Coincidentally, 3-4 hours per day is about how long these bulbs might be "on," so it seems my six-bulb array is a good test track. Results:
1 bulb burnt out in about a year and had to be replaced. A second one began flickering uncontrollably about a month ago at less than two years of age and had to be replaced. Conclusion: the average life of these six bulbs is now down to just a bit over 15 years, and that is ONLY if each of the remaining four lasts 22+ years. What are the odds? Given the track record so far, not great. Meanwhile as the replacements - which may or may not last 22.8 years! - have been added, my cost has increased by 33%.
Guarantee? Yes, nominally these bulbs are guaranteed for 5 years - if you have the original receipt and can return them to the retailer (not the manufacturer!). How many people will actually do that? Personally, I thought I had kept my receipt but I'm having some trouble finding it...
The end: There are a number of possible lessons to be learned here. For many, unfortunately, it is: "Don't buy LED bulbs, they are a bad bargain." Given the state of global warming, though, I think the real lesson is different: Coal is still cheaper than solar, wind, or nuclear energy, but we are gradually reducing our use of coal (in fact U.S. coal companies are in financial trouble at present). Over time, the same will be true of the simple light bulb.
The new lesson? We will have to face the fact that for many years to come, the essential things we need to do for the environment are just going to cost us more. Cost is important, and will come down eventually, but in the short run, we can't "afford" to try to sell solutions on a cost-efficiency basis. Unless, of course, we find a way to quantify the hidden costs of doing nothing, e.g. with coal it's the pollution of air, soil and water; the desolation of landscapes; the effects on our health.