A true life test of an LED bulb would last at least ten years or more. That's a long time to wait for verification of lifetime claims made by LED bulb makers, and is also a long time to wait for confirmation of parameters that go into awarding Energy Star ratings to lighting products. So the typical way of testing the lifetime of LED illumination products is to do accelerated life tests and computer modeling that predicts a time-to-failure.

Nevertheless, a few agencies running life tests on LEDs are now starting to get results for lengthy partial life tests of the devices. For example, Consumer Reports recently reported on its ongoing tests of six LEDs. CR says it has been running the tests for 12,500 hours — equivalent to more than 11 years of use when turned on for three hours a day. In these tests, most of the LEDs are as bright as they were after 3,000 hours of testing and are also still accurately showing the colors of objects and providing the same light color. CR contends that these results show the bulbs they've tested "easily paid for themselves," with the expection of one bulb: The EcoSmart PAR38 ECS 38 Bright 75W 866194 Dimmable LED, $33, a replacement for a 75-W flood/reflector bulb. Four of the 10 CR tested didn't last 12,500 hours. Even so, the first of these bulbs to die lasted the equivalent of eight years and would have saved buyers around $50, CR said. The other three lasted the equivalent of eight to 11 years.

CR also says its tests reveal that a decent LED replacement for a general-purpose 60-W bulb is the Philips AmbientLED 12.5-W 12E26A60 60W 409904. CR says it is bright, gives off a warm yellow light, and is dimmable. After 12,500 hours of testing at CR, it still has an overall score of 98. CR also says at $25 the LED takes about 3.8 years to pay for itself and is supposed to last 25,000 hours.

CR had good things to say about Home Depot’s EcoSmart 9.5-W (65 W) LED Downlight (E) ECO 575L, $27, which replaces a 65-W flood or reflector bulb used in a 6-in can. Its warm light is dimmable, and colors of objects appear more accurately than with most LEDs. CR says it has performed well after 12,500 hours and is claimed to last 35,000 hours. CR figures the payback time is about two years.

The CR figures are a good rule of thumb, but if you want to figure your own return on investment for LED bulbs, you could try the online calculator maintained by Pat Mullins.