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Does a burnt out florescent light bulb use the same amount of energy as new florescent light bulb does

Bill Worthington
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    Where fluorescent lamps have a difference is more in the light output when new let’s call this 100% in just a few month the output drops by 25% or more and continues to have less light output. A lamp is considered at end of life at 50% but I see them all the time much lower than this but the ballast keeps the power constant so a lamp at end of life uses the same amount of power but is providing much less light. – Ed Beal Apr 02 '22 at 04:40

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No, a burned out fluorescent tube doesn't use any power at all. It is an "arc light", and if the arc has not struck, then there is zero current.

Power is Watts = Volts x Amps. If Amps is 0, then Watts is 0.

If the filaments at the end are glowing (the pre-heaters) it's using a couple of watts at most.

There will be a few watts of load in the ballast, depending on the technology of ballast (a lot more for an old transformer-based "magnetic ballast", very little for a modern electronic ballast).

Harper - Reinstate Monica
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It's more about the ballast than the lamp. Most modern ballasts are electronic which can sense how much power is demanded and only provide that amount to flow. Old-style autotransformer type ballasts, because of their design, let current flow whether there is a lamp in the fixture or not.

ThreePhaseEel
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Retired Master Electrician
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