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Comment by capty99

3 hours ago

could someone explain to me how that $5 spend is lying to me. i know elec is cheap, but that cheap?

$5 does not make sense, and there must be some qualifer on that we're missing.

Napkin math:

(27 minute flight) * (25000 lbm TOGW) * (Earth gravity) / (~10 average L/D) * (160 KTAS average) / (70% propulsive efficiency) / (97% coulombic efficiency) * ($50/MWh) = $30

(Add residual kinetic energy upon landing too)

Side note: Heart also has a weight issue here they'll need to overcome if they want to certify under FAR Part 23 (as their 19-pax spec implies); TOGW limit for that is 19,000 lbm.

They’re using wholesale prices. The entire flight was 27 minutes, peaked at a megawatt of power, and a wholesale megawatt-hour is $40-50 these days.

I tried to run a napkin calculation, and that 5$ figure must be quoted per seat (30 seats). And a 'first flight' might be very very short, like 15 minutes of flying or less.

During certain hours of the day in California, electricity is essentially free due to solar overproduction, which sometimes causes negative wholesale prices.

  • I've never quite understood negative electric/gas/oil prices.

    Are you literally paid for agreeing to receive the energy?

    • Yes. Counterintuitive, but it make sense when you take all the factors into account (such that completely shutting down and then later restarting turbines may cost a generator more than paying someone to take power off their hands).

    • Yep. Last August the total cost to charge my car for the month was -10SEK of about -$1.05 US, as my energy company was trying to put load into its batteries at the times when the grid most needed it.

      2 replies →

    • Yes, if you’re a battery in the system. Basically discourages generation because there’s too much supply. But this generally doesn’t trickle to consumers afaik.

    • Easiest to understand with oil. During Covid the price of oil went negative. So you’d be paid if you bought that oil.

      Sounds like a great deal right? But now you’re on the hook for receiving and storing that oil. That costs money, it’s not free. That’s why the price went negative - the seller was trying to offload and there were no takers at $0.