Numerous questions and comments have indicated to us that a lot of drivers are interested in the service life of halogen lamps in car headlights. In this second part of our series, we give you the facts and figures.

Some drivers would like to know exactly how many kilometers or months their headlamps will last. But figures like that are impossible to calculate. Lamp life can only be stated in hours of operation, just like a car engine, which is said to have a life of around 6,000 hours.

Who wants long service life, should use a long-life lamp, such as the Ultra Life of Osram.


For lamps, the manufacturers give two numbers: B3 and Tc. B3 indicates the minimum number of hours 97 percent of the lamps (i.e. virtually all) last. After this time elapses, the frequency of failure starts to increase. By the time the Tc value is reached, 63 percent of the lamps likely have failed. Sorry if it sounds so complicated, but it isn’t that simple for all lamps of one type to last x-many hours and then to suddenly and collectively give up the ghost (although premium products do have very similar service lives due to their close tolerances).

Osram puts its cards on the table. The company lists the values for B3 and Tc. For a standard H7 lamp, the B3 value is 330 hours. To compare, a dual filament lamp from the 1960s gave off much less light and failed after around 50 hours. A modern high-performance lamp, such as the Night Breaker Plus, emanates full light for at least 150 hours. For the bluish Cool Blue, the B3 value is 100 hours. If that seems too low for you, you can choose a long-life lamp. These lamp types in the H7 version will give you over 1,000 hours of bright enjoyment (albeit not so bright as the types mentioned before).

Incidentally, these numbers apply for a test voltage of 13.2 volts. Watch this space for information on how a car’s operating voltage affects lamp life.

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  • You say the Ultralife is dimmer? So how come the Night breaker, the standard Original Line, the cool blue, and the Ultralife H7 bulbs are all rated at 1500 lumens +- 10% i.e. the ECE limit?

    • Dear Bernard,
      All the named lamps deliver a luminous flux of 1500 Lumens and, you are right, ten percent tolerance is allowed. But luminous flux is only one of the parameters for the light on the road. Luminance is very important, too. You may call it light intensity and it is defined as luminous flux per area. To be most precisely: Candela per square meter. Higher luminance in the filament is beneficial and that is where the other lamps can be better as longlife versions. It is physics. Hope this helps.
      Best regards,
      your carlightblog team