Item — HN Reader

>> Power is not free.

There's actually an interesting thought experiment here: if it takes you a full day to build something that AI would otherwise build in a day, do you end up using more power, or less? What is the break-even point, purely from a power consumption perspective?

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If an identical task takes a day on both sides, then the human route uses less energy, surely.

Brains are thousands or maybe even millions of times more fuel-efficient than computers and you are alive for the whole day either way, right? You probably eat about the same even.

The reason executives think AI is more efficient is that it more space efficient than a human and doesn't demand to be paid or work only a set number of hours. Everything with computing is more efficient if you resent having to give money to other humans. If they could just not have you be alive when they don't need you, it'd possibly be different.

Even though I think at a typical British freelance rate and a truly unsubsidised token price, the AI is possibly more expensive than me. And as a freelancer, from their perspective I really am not alive until they need me. (This is what it often feels like)

The reality is the human and the AI aren't used to build the same things anyway so it's a comparison you can't really make.

Brains are efficient, but civilized humans aren't. In the USA, adults consume at a rate of about 10kW -- only 1-2% of that being the human's metabolism, the rest being HVAC, electrical devices, etc.

For comparison, a modern frontier model like Gemini 3.5 Pro consumes about 15kW -- so only about 1.5x the fully loaded human. In an 8h workday, that model would crank through ~80M tokens (~$5k at API prices). That's ~4 major refactors of a 10k LOC codebase, so probably not a very realistic comparison to a single human dev.

I think a more useful comparison, based on my experience, is that an engineer with AI support can get one 8h day's worth of unassisted work done in 1h. So, the 25 kWh consumed during collaboration (conservatively assuming I keep the GPU hot for the whole hour) frees up the remaining 70 kWh I'll draw down for the day to be spent in some other way.

You forgot to mention that it takes a lot more energy to train that human before they're able to work.

The human in the scenario is on regardless. One has to assume. But I also think this sentence you typed is essentially a single line horror story and we should consider whether it is ever appropriate to say it out loud.

to be pedantic you'd need to think a lot about how you power your human. Did you fuel up your human with beef or beans? local or shipped? were they operating a day in climate control? have to commute? did they need equipment like a large monitor? etc .

in reality basically all those concerns come out in the wash when you factor pay. energy inputs throughout the chain tend to materialize as expense. if the human was paid less then likely they used less energy.

Studies on grandmaster chess players indicate that at most you burn 10% more calories when engaged in deep thought than when you're at rest. So the energy "attributable" to an hour of knowledge work is like 10 calories (average sedentary calorie burn is like 80-100 per hour; add a max of 10% for the thinking gets you 8-10 calories). A pound of potatoes is like a buck and is about 320 calories. So you're looking at like 3 cents an hour at most to cover that energy burn. It's definitely even less; I certainly don't think as hard as a grandmaster chess player.

Then, assume power costs 20 cents per kilowatt hour (US avwrage) To match the human 3 cents per hour, you need an average of 150 watts of power drawn per hour. That's in the range of a budget graphics card, but not much past there.

However, if you sleep instead of sitting around, you can probably make AI cost competitive. Sleeping drops your metabolic rate by more, and lying down in bed (as opposed to sitting) also reduces calorie burn. Combined, you can reduce your burn by like 30 calories an hour. At the new 9 cents per hour human cost, you can afford to run a higher end graphics card at ~450 watts per hour. That puts you in RTX 3090 range.

Excellent analysis, and

> However, if you sleep instead of sitting around, you can probably make AI cost competitive.

important consideration.

Yeah, it gets weird when you start trying to compare human versus AI energy demands because you can turn a computer off, but you can't really turn a human off. Most studies indicate that humans can do 3-4 hours of high-level knowledge work in a day. An AI is not limited by these restrictions; it could do 24 straight hours of work if you wanted it to. So do we count all the energy the human burned for the remaining 20 hours of the day and allocate it to those 4 hours? Or are we just comparing "energy spent working on the task" for the AI and the human?

The jokes are aside now!

Maybe we gotta include all 24, since no one will ever* get the 4 without the 20 of sleep/eat/relax.

*least probably not long term with FTEs I assume

Though for employers who send employees home it should be OK to ignore what employees do outside of work…

What would you do for the rest of the day, power off your devices and go for a long bike ride?

Speaking personally: yes. That's literally what I'm planning to do this afternoon because it's noon and I'm already done with the coding tasks I had on my plate today.

Luckily the future is absolutely going to be that star trek one where technological abundance means we are all wealthy and have free time to develop personally, and not the future where all the money bubbles up into the hands of a thin-skinned malignant narcissist who wants to play with launching rockets and provoking racial violence /s

The question needs to be tweaked a little: it's not just human vs LLM, it's human vs human + LLM, which makes the calculations easier (and more correct because LLMs don't currently operate independently.)

I've run the napkin math, and assuming LLMs make humans even 5% more efficient, the power and water savings over time are significant, largely because humans are so resource intensive: https://news.ycombinator.com/item?id=46984659

There is no break even point, you always come out ahead doing it yourself because your caloric burn is the same for the day whether you build the tool or AI builds the tool. Only way the AI example might avoid that is if it tells you to jump off a cliff before starting the compute run.

I'm assuming that you need to feed the human being (i.e. you) regardless of whether you use that human being for writing code or not. So, by this metric, there is simply no breaking even point. The cost of human + AI is always going to be higher than the cost of human.