Rated life is the median life of a sample group, so by definition some lamps will not achieve the full rated life. In addition, incandescent lamp life can be shortened by vibration or shock and supply voltage swings. If a bulb is going to be in an environment where it is exposed to vibration or shock, such as a garage door opener light or ceiling fan, you should try to use a lamp with a stronger filament. Keep in mind that stronger filament bulbs will be less energy efficient.

Another cause of continuing general incandescent lamp failure [other than leaving them on all the time] is high voltage. While utilities usually do a pretty good job of voltage regulation, they sometimes have little control. State regulatory boards allow them certain specified leeway because of anticipated Load, local Load peaks, and other criteria. The allowable limits are usually in the order of ten percent, which on your nominal house voltage of 120 volts would allow a range from 108 to 132.

Incandescent bulbs are very sensitive to voltage. A lamp rated at 120 volts, for example, would only last 1/2 of rated life if subjected to 125 volts or 1/3 of rating if the average voltage applied were 130 volts.

The first thing you should do is to keep track of how long the worst offenders are lasting. How long are your lamps burning? Be sure not to count the time that they are turned off. Typical incandescent bulbs are rated at 750-1000 hours, meaning approximately 2-1/2 changes per year [at about 5-7 hours per day]. The next step may not be easy and should only be undertaken by a licensed electrician. The only way to determine the average voltage your bulbs are experiencing is to attach a recording voltmeter to the circuit you are testing so that it records only when your lights are on. If your electrician determines that you are receiving higher than rated voltage you will need to contact your electric utility to fix it.

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