There's an episode in The Green Mile movie where the death row servicemen rehearse the upcoming execution that is done using an electric chair. One of them says (quoted from here):

Roll on one. [pause] "Roll on one" means I turn the generator up full. The lights go brighter in half the prison.

he says that and indeed ceiling lights in the building go brighter.

Which implies that the electric chair requires a generator that produces suitable voltage and also adds extra power required to sustain the peak power consumption of the chair. This part makes sense.

But the "lights go brighter" part implies that the generator is somehow connected to the mains in the prison. This makes no sense to me - connecting a high-voltage (more than a kilovolt) generator to 110 volts mains would cause electrical problems and would likely not give any advantage.

I couldn't find any evidence of such setups - electric chair powered by a generator connected in any way to the mains of the building. Do such setups exist?

  • 3
    I don't see a contradiction here. I imagine the generator produces 110V and there is a transformer between the mains and the electric chair.
    – Jader Dias
    Jul 21, 2011 at 11:47
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    you already answered that. The generator is connected to the mains. The transformer draws energy from the mains.
    – Jader Dias
    Jul 21, 2011 at 11:55
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    @Jader Dias: Assuming the 110 volts generator is connected to 110 volts mains the voltage should remain 110 volts, shouldn't it? If it remains the same the lights should not go brighter.
    – sharptooth
    Jul 21, 2011 at 12:00
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    not if the voltages are slightly different, it never happened to you that a power hungry electrical appliance in your house diminished the lights when on? That's because consumption subtracted a few Volts from the mains. The opposite can happen when you have a generator.
    – Jader Dias
    Jul 21, 2011 at 12:19
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    It could make sense to connect the generator to the mains: because apart from being used in electrocutions, the generator would also be used for backup power (to the prison lights) if the mains electricity failed (in the same way that generators are also present in hospitals and in telephone exchanges).
    – ChrisW
    Jul 21, 2011 at 12:21

2 Answers 2


In this article from 1976 regarding Texas reactivating their electric chair after the death penalty moratorium imposed by the US Supreme Court was lifted, the article specifically mentions the generators used for the electric power to the chair.

This gizmodo story about Ted Bundy's execution also mentions the diesel generators used to power Florida's electric chair.

Why a generator is used when utility power is more than sufficient is another matter. This may be to avoid the possibility of a power failure and a botched execution.

The 'dimming of the lights' seen in this video of a last Bundy interview, when Florida was testing the electric chair for him, was actually the prison switching over from utility power to the backup generators.


OK, did more Googling.

Louisiana used a portable electric chair, nicknamed Gruesome Gertie, which is now in a prison museum. The chair was brought in a panel van to the parish (county) jail where the condemned man was imprisoned. The chair was powered by a generator running from the van engine. [Source: "Old Sparky: The Electric Chair and the History of the Death Penalty"]

Setting up the Louisiana generator is a scene in the novel "A Lesson Before Dying", which was inspired by an actual Louisiana execution.

  • Why was the condemned imprisoned in a panel van?
    – phoog
    May 17, 2018 at 2:20
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    No, the chair and generator were brought to the jail in a van. The condemned man was in a cell. The novel has a scene for setting the chair up, but I forget exactly where—I think it's inside with the wires run through a window—that probably was taken from the actual event modeled. May 17, 2018 at 2:45
  • Did they also use the generator and the van for supplying popcorn for the execution spectators? Seems like dual purpose food/generator use would be a great business opportunity. Aug 20, 2018 at 15:47

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