When buying an LED flashlight, people want to know how long they’re going to work. Because LED light bulbs are so durable and energy-efficient, they tend to last much longer than other types of bulbs; some manufacturers claim their LED flashlights have a life span of many thousands of hours. But how far can you really believe such packaging claims?
It helps to understand how a flashlight is tested when determining the life of its LED light bulb. LED flashlights are typically tested in two ways: first to see how long the product works, and then to see how well it works during that time. As a result, LED flashlights typically receive two life span ratings – rated life and lumen-maintenance life.
Here’s a look at how these two ratings differ:
Rated Life of an LED Flashlight
The rated life of an LED flashlight is a statistical estimate of how many hours the LED light bulb will work. This value is also sometimes known as the Bp rating, in which p is the percentage of tested flashlights that failed in a given time.
For example, if an LED flashlight has a B10 rated life of 1,000 hours, that means only 10 percent of the flashlights tested failed within that time. Consumers can expect this product to last much longer than a flashlight with a B50 rated life of 1,000 hours (which means half of the flashlights tested failed within that time).
Lumen-Maintenance Life of an LED Flashlight
All light sources will gradually decrease in the amount of light they emit over time, and LED light bulbs are no exception. This phenomenon is known as lumen depreciation, and it is indicated by a measurement known as lumen-maintenance life.
The test for lumen-maintenance life involves leaving a bulb on for a specified length of time and measuring how bright the light is at the end of that time. The measurement is usually written as Lp, with p indicating the percentage of brightness remaining. So if an LED flashlight has an L85 rating of 50,000, it means that after 50,000 hours, the flashlight will continue operating at 85 percent of its initial brightness.
To put the two ratings together: If an LED flashlight has a B10L50 rating of 30,000 hours – about three and a half years – that means the flashlight has a 10 percent chance of failing within that time; otherwise, it will continue to operate at half its initial brightness.