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points by bryanlarsen 1 day ago | 0 comments

Driving is wasteful. Cybertrucks and Prius's use similar amounts of energy per mile. Cybertruck is 0.4-0.5 kWh/mile, the Prius is 0.6-0.7 kWh/mile.

Of course the Prius Prime on electricity is way more efficient than both, but it still uses a lot more energy than a house.

[–] pintxo 1 day ago

European units (`Energy/100km`) work nicely here, lots of EVs are around `20 kWh/100km`, and most residential housing around here consumes less than `20kWh/day`, actually averaging `20kWh/day` would probably cover a well insulated house including heating (heatpump).

Yes, driving, compared to living, uses ridiculous amounts of energy.

[–] dllu 1 day ago

With dimensional analysis you can cancel it all the way out until it's just Newtons, which is actually just the average drag force times some efficiency multiplier.

[–] jaggederest 1 day ago

Dimensional analysis is a superpower honestly. Even in a software engineering career it's saved me from massive issues quite routinely

[–] vpmadd52huq 1 day ago

Mandatory XKCD: https://xkcd.com/3038/

[–] dllu 1 day ago

Also: https://xkcd.com/687/

[–] NetMageSCW 1 day ago

The HP 48G / 50G provides incredible unit handling. My main use for it these days.

[–] selimthegrim 1 day ago

Any war stories?

[–] jaggederest 1 day ago

Requests per second, bytes per request, bytes per second should all match up very closely under dimensional analysis or something is drastically wrong ;)

Little's law is another related phenomenon that is super critical. Measuring things when the units don't match has bitten me more than once.

[–] selimthegrim 1 day ago

Concur on Little's law

[–] gertlex 1 day ago

I'm curious if you can elaborate further? Would that make the comparison clearer, or is it just a side-note on your part?

[–] dllu 1 day ago

Work (energy) is force times distance. Since we're talking about energy divided by distance, it's actually just average force.

Actually newtons are just a constant factor (3.6) compared to Wh per km, since there are 3600 seconds in a hour while there are 1000 watts in a kilowatt. For example 144 Wh/km (or 14.4 kWh/100 km) would simply be 518 N. This also means that pushing along a Tesla on the highway at constant speed is roughly as hard as holding a 50 kg weight, giving you an intuitive sense of how "hard" it is to keep things moving.

Of course, in everyday life, since we buy electricity from our utilities in kWh rather than joules, it's more convenient to talk about kWh per km (or per mile).

[–] gertlex 1 day ago

Thanks. Was there a particular reason I'm not grasping for noting that on the comment you replied to? Seems like a comment that could be stated about any comment tackling about energy/distance.

Actually, I guess the comment you replied to was also not really clear in it's point, so I'll blame that guy for maybe diverging from the topic somewhat :)

(not trying to be negative, really! but my brain is a bit fuzzy from being sick, so thus feeling a bit dimwitted as I ponder comments)

[–] hamdingers 1 day ago

For comparison my cargo ebike, which is not particularly efficient, consumes about 30 Wh/mi (0.03kWh/mi) in medium assist while transporting an adult and two kids.

[–] SequoiaHope 1 day ago

My road bike consumes energy bars! And fruit!

[–] tga_d 1 day ago

Surprisingly enough, this makes acoustic bikes less carbon efficient per unit distance than electric ones, depending on the details of your diet. Of course, once the emissions are that low, this is more a curiosity than actionable insight (beyond the typical "less meat/dairy = lower emissions").

https://www.youtube.com/watch?v=HW5b8_KBtT8

[–] SequoiaHope 6 hours ago

Yaaa I’m vegan which helps a lot! A solar powered ebike is probably more resource efficient tho.

[–] sportsracersss 1 day ago

"Acoustic" bike? What is this madness?

I thought you were autocorrected badly but I guess this is a term people use?

[–] eclarkso 1 day ago

It's a joke referencing electric vs. acoustic guitars.

[–] s-zeng 1 day ago

What a coincidence, my cargo bike that regularly takes 50kg of cargo runs on the same stuff !

[–] DonHopkins 1 day ago

So you ride around town in a PacMan? Aren't ghosts a problem?

[–] RankingMember 1 day ago

Just gotta always have a Power Pellet in range

[–] RankingMember 1 day ago

I get 30 miles per sandwich! Beat that EV owners! :P

[–] solyin 1 day ago

What's in that sandwich though? The Cybertruck using California non-renewable energy creates 162g of CO2 per mile. A sandwich full of lamb generates 666g. A sandwich of lentils does 40g.

[–] barbazoo 1 day ago

Are those numbers right? 0.4 kWh/mile is 24.85 kWh/100km compared to about 14 kWh/100km my Kia Niro EV uses.

[–] bryanlarsen 1 day ago

Those numbers are saying that:

- the Cybertruck uses almost twice as much energy as your Niro EV

- the 40% efficient Prius uses about 2.5x as much energy as your 95% efficient Niro EV.

what seems off?

[–] benatkin 1 day ago

Driving uses a lot of energy. It's wasteful if you aren't getting a good use out of it (of which just driving around to relax could me considered a good use, but of which some manager requiring RTO might not be).

[–] pembrook 22 hours ago

Driving is not wasteful. Energy is not a scarce thing in the universe.

Using energy is not bad. Creating excess carbon emissions is bad.

We need to be able to hold two ideas in our heads instead of blindly repeating trendy religious dogma.