Comment by brudgers | Hacker News Reader

Comment by brudgers | Hacker News Reader

I've been nerd-sniped into google fueled napkin math.

  18kw/100 m = 180kw/km

The most powerful Swiss electric locomotive [1] maxes out at 7900kw. That's 44km of track.

The most common Swiss electric (4/4) typicaly maxes at 6100kw requiring up to 34km of track.

Switzeraland has about 5000km of track and 180 is about 200, so a million kilowatts if all the track has solar panels.

Assuming 3000kw per locomotive and 100% efficiency [2], that's 300 electrical locomotives running simultaneously. The Swiss fleet is about four times that.

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Of course I am no expert.

[1] https://en.wikipedia.org/wiki/List_of_stock_used_by_Swiss_Fe...

[2] and ignoring the 10 per year efficiency loss of the panels mentioned in the article

You don't need peak power all the time. The point of trains is that they're extremely efficient; most of the time they're essentially coasting, they only need a lot of power when accelerating or ascending.

If you want hard numbers, SBB used 1685GWh for passenger trains in 2025 [0].

The bigger problem with this idea is solar in Switzerland. It's fantastic during the summer but close to nonexistent during the winter [1]. Trains need to run year-round, so you'd need to overbuild solar monstrously to power SBB during the winter, or you'd need to solve seasonal electricity storage, which isn't easy. Pumped hydro is great but Switzerland has already built about as many artificial alpine lakes as the population is likely to tolerate.

[0]: https://reporting.sbb.ch/en/sustainability?=&years=5,6,7,1&s...

[1]: https://energiedashboard.admin.ch/strom/produktion

You don't need peak power all the time

3000kw is about 1/2 power for the most common Swiss electric engines.

And peak demand determines grid size.

> they only need a lot of power when accelerating or ascending.

Regenerative breaking on trains is a thing.

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