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Comment by apt-apt-apt-apt | Hacker News Reader

I saw a guy (in america) charge his e-bike battery once at Starbucks. GPT estimates a full recharge to be around 30 cents.

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Hah, probably comparable to running a desktop for an equivalent amount of time - most ebike chargers are 100 - 200 W, and the bikes usually have a battery between 0.5 - 1 kWh (which in my area would be 5 - 10 cents). Less disruptive though, assuming they detached the battery and left the bike outside.

  >GPT estimates (...)

Dude it's middle school math. Average pedal assist e-bike battery, estimate at 500 watt-hours. Electricity prices at my home are about 20 cents per kilowatt-hour.

(0.5 kwhr) * (20 cents/kwhr) = 10 cents. With an additional 10-15% due to charging system inefficiencies (lost to heat). 11 cents.

It can be good exercise to do an 8th grade level word problem every now and then.

The actual arithmetic is easy but most people don’t know about the batteries in e-bikes. They might not know about the electricity prices at the top of their heads either.

You could google those…but it seems easier to just use GPT if you’re going to google that stuff anyway.

Well considering the GPT reported '30 cents' a charge, it is either a. considering 3x larger battery than I would consider average e-bike sized (and I got my 500Wh number based on a 10-second google scan), b. price of electricity it is considering is 3x higher (highly doubt it) or c. it is imagining that modern lithium ion charging efficiencies wall-to-battery are way, way worse than they actually are (possible to hallucinate and integrate into its calculation).

Either way, we don't know, and the original commenter doesn't know either, because they didn't google anything about e-bike battery sizes or their local electricity prices and thus didn't take the opportunity to actually learn something.

The estimate was based on a battery of 750Wh (bikes seem to range .5-1 KWh) and CA prices are around 30 cents/KWh. That's 2.25x your meanly worded estimate.

I did learn how simple the cost calculation is though (capacity * $/KWh), thanks.

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