Head End Power (HEP) is the electrical power supplied from the locomotive to the passenger cars for lighting, heating, air conditioning and other amenities - essentially the "hotel load" that keeps your private car functioning while attached to the train.

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Llamamoe 6 days ago | parent [-]

Why is it so much? I can't imagine a few lighting and heating fixtures using several thousands worth of electricity.

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Ambroos 6 days ago | parent | next [-]

Power generated on a train is probably significantly more expensive than power you can pull from the grid. Most of Amtrak's network does not have power so I assume they rely on generators on the train.

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bombcar 6 days ago | parent | next [-]

It’s also called “hotel” power and is provided by the locomotive, but separate from “needed to run” power. A train can run with just air and the physical connection, hotel comes with the big “other cable” connected.

Some private cars do NOT use it and instead have their own generator. In theory you could have one with no lights, etc at all.

I’ve been on an Amtrak where it lost hotel power; nothing but emergency lighting until they got to a station where they could swap the locomotive.

But the train kept running, and the conductor had to walk the entire train announcing stops verbally; with no PA system.

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mcculley 5 days ago | parent | next [-]

> with no PA system

Wow. That is crazy and surprising. I can see losing air conditioning, but the PA should be considered mission critical.

	▲	starkparker 5 days ago \| parent [-]
		The toilets also rely on electricity to flush, which is where the real nightmares begin on any sufficiently sold train of 2+ hours.

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Llamamoe 5 days ago | parent | prev [-]

Why can't the locomotive pull it from the wires? It's not like it maintains a constant draw with all the speed changes and such.

	▲	AnimalMuppet 5 days ago \| parent [-]
		Most of the US doesn't have wires.

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namibj 6 days ago | parent | prev [-]

It's from the loco which in the US almost exclusively used electric propulsion, just for capex vs. opex balance sheet gaming reasons mostly (except in and around NYC (tunnels) and some very recent electrification efforts (I think bright line in FL was looking at electrifying some trains? Something recently did and improved performance that way.) sourced from medium speed diesel generators housed in the loco.

Way back in the day of steam heating was via open-cycle steam and electric lighting via generators on passenger car axles with a local battery to keep the lights on while stopped.

Eventually with the end of steam they switched to electric heating and can conveniently siphon off electric lights from that.

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IsTom 6 days ago | parent | prev [-]

OTOH if you want a bunch refrigerator cars it might take a bit more power.