Updated: January 30, 2026
When I first saw The Matrix roughly a quarter of a century ago, like many a young nerd at the time, I was thoroughly impressed. The movie was visually spectacular and quite revolutionary, with its slick use of bullet time and AI-related philosophy. Indeed, thanks to The Matrix, lots of FOSS developers still think oppressive dark themes with a glaring green tint are the correct way of doing user interfaces. The notion of life inside a simulation is another rather popular theme. Quotes, check. Red pill, blue bill, golly! I remembered the film as entertaining, fast-paced, tense, nice. Then, I watched it again several weeks ago, and, ugh, it didn't age well.
To me, nowadays, the techno-grunge leather, neon lighting and pseudo-philosophy look all utterly outdated. The concept of yet another AI robotic apocalypse seems cliche. There's no romance whatsoever between Neo and Trinity, the conversations feel stilted, and the action isn't as actiony as I remembered. Far from it. But the worst part is the use of humans as fuel. I can't honestly say what my impression of this bio hazard was back then, but I'm sure feeling mightily skeptical now. So I thought, let's actually calculate whether humans would ever make for a practical fodder for robots and alike.
Hence image craftfully made in Linux, with cmatrix, in a black terminal with green text.
The original story ...
From what I was able to glean off the Internet, the first script called for humans being used as "intellectual" fuel, i.e., their brains would be used as neural fodder for machine simulations and computations. On its own, that might have some merit. Indeed, in the movie, there's an important scene where Agent Smith explains to Morpheus the concepts of simulation, and how first AI models failed when humans didn't "live" in a world. Supposedly, 1999 was peak. In retrospect, considering all the technological changes we've experienced since, this ain't that far from the truth. This may be yet another resonating, culturally useful and lasting aspect of The Matrix.
However, since the idea of using human brains as CPU and memory wasn't shocking or bombastic enough, the apocalypse had to be transformed from a mathematical one into a mega-flesh-factory concept that doesn't stand the test of basic physics. So here we are. Now, let's crunch numbers.
The answer is no
There are many many many reasons why humans aren't useful as fuel.
First, the humans are mostly water. That makes them rather impractical, even as kindling. Plus there are much better, energy-dense alternatives out there. Really. Soooo much better. You don't need any fancy calculations to realize this. But let's.
If you consult the energy density article on Wikipedia, you will see that you can extract maybe 45 MJ/kg for liquid carbon-based fuels, of which water isn't on the list, whereas fancy stuff like nuclear fission offers, without any need for futuristic fusion or anti-matter, about 30-80 million MJ/kg of energy. Yes. That's not a typo. This is six orders of magnitude more than anything else. That's all that matters. There's nothing else to say really. Chemical fuels aren't even remotely competitive with nuclear. But let's play along. Human fuel it is.
Nuclear, still the best source of energy, by far.
Note: Image taken from Wikipedia, licensed under CC BY-SA 4.0.
In industrial design and planning, as a crude black body, and considering human caloric intake, a typical human at rest is considered to give off about 100-120 W of heat. For simplicity sake, let's assume that one human = 100 W. Let's also assume that the evil Matrix breeder farms contain 10 billion humans.
All in total, we're generating a rather unimpressive 1 TW of (low) heat.
Is that a lot?
First, it is not a lot, this magical 1 TW.
If we look at what sort of nuclear reactors we have in the world, and consult some references, a typical nuclear reactor generates about 1 GW of power, but this goes up to 1.8 GW. For instance, RBMK-1500 does a neat 1.5 GW, whereas the brand-new gen 3+ pressurized water reactors like EPR return 1.6-1.77 GW output. Thus, we would merely need about 650 of these reactors to match the energy output of humans. Lo and behold, in 2025, there are 430 active nuclear reactors in the world. The Matrix scenario calls for a rather humble 40% increase, without any big apocalypse. Let's call it double. Still, no big deal.
Second, it's not a lot regardless. In 2021, the US energy production alone was more than this number. One country, four years ago, not taking into account all the other 190 territories. Even the UK generates about 41 GW, which would be similar to France, Germany or maybe Spain. All in all, it takes perhaps 20 developed countries to get to the magical number once again, even without the US figures.
Now, you could say, but wait, the machines could have their giant breeder farms with 100 billion humans!
Sure, and now, let's consider another factor ...
There's not such thing as a free meal
Overall, humans also aren't very efficient as potential fuel, because we need to consume about as much as we emit as heat. Thus, 2,500 kcal in, 2,500 kcal out. The real value of humans is in our communication abilities, our use of hands and digits for fine, precision work, sheer intellectual output, and then, at the very end of this list, some mechanical labor. It sure isn't in how much we sweat. A typical ox or a plow horse is way more efficient as a crude automaton than any one human.
Indeed, if the machines and robots were to harvest humans for their heat, or whatever, then:
- Each pod containing a human needs to be built and maintained.
- The humans need to be fed - where exactly do nutrients come from? Are robots actually manufacturing synthetic fat, protein, carbs, and vitamins to sustain their giant nurseries? How much energy goes into producing the food?
- The robotic sentinels also need fuel to work.
- The energy needs to be collected, transported down the chain. If each pod is a battery so to speak, then we need transformators, aggregators, all sorts of substations that would direct the energy to wherever it's required. This implies yet more energy losses.
You're better off growing beans than humans. For realz.
Note: Image taken from Wikimedia, licensed under CC BY-SA 2.0.
If we start with 1 TW, soon enough, the efficiency goes down. A lot. I'm quite confident that any system built to utilize whatever humans produce as a potential source of fuel (from heat to urine to anything) will generate a significant net loss. In other words, any such system would require more Joules than it would ever give back.
Don't believe me? Look at human babies, which would not be that different from the ones kept in the simulation pods in The Matrix. They eat, they sleep, they don't produce anything. They sure don't produce any sort of useful energy or heat that would contribute back to the household and their parents. If anything, speaking of heat, typically, you need to crank the interior temperature up to keep the babies cozy.
Lukewarm, shaken, not stirred
But let's be extra optimistic. Even if humans produced perfect heat with minimal parasitic loss in the system, the heat we emit is at comfy 37 degrees Celsius, slightly less than a typical giacuzzi in a spa. Such heat is not "hot" enough to sustain most or any processes that could be utilized for energy conversion. Good enough for metabolic processes inside our body, not good enough for anything else.
For instance, if you can boil water, then at least you can use the steam to propel turbines to generate electricity. But 37 degrees? At best, this heat could be used to warm up sandwiches for the machines. But on its own, without additional work, which takes extra energy, human heat is useless.
Look at it this way. Our very planet generates tons and tons and tons of heat from its core and the radioactive isotopes in the mantle. But this heat is not really useful, other than to create the basic conditions for organic life. Technically, the planet is just warm enough to allow oceans to exist in liquid form, and for soil to sprout plants, and then, it comes down to solar energy to help push things along. In essence, we need a star.
Still, all this heat is out there. But you can't just "scoop" it out of thin air and do anything meaningful with it. If this heat was useful, then humans wouldn't need warm clothes, fire or metallurgy. The reason we developed these tools is to be able to create things that are not possible at room temperature.
Indeed, low-heat engines usually have only about 3% efficiency. As an extreme example, the Hadley Cell is probably the best example of a giant, natural heat engine, with an average power output of 198 TW and a thermodynamic efficiency of 2.6% over a period 40 years. So yes, here we have a system that contains about 200 more energy than all of human heat combined, and even with the meager efficiency it has, it would still offer about 5x more useful power than podded humans under ideal conditions. It would make more sense to create atmospheric engines, wind mills, or oceanic wave power stations than anything made from meat and bones.
To make things even worse for The Matrix design, there's one more aspect that we ought to mention. The podded humans also need to be kept warm. For a naked human body at rest, the ideal homeostatic temperature is around 27 degrees Celsius. That means our bodies produce a useful delta of only 10 degrees, which could be converted to other forms of energy. Whatever we discussed earlier, it's even worse than that.
Thus, in the end, it doesn't matter if there are ten or hundred billion human pods in the system. It makes no difference. And actually, since The Matrix is a simulation of 1999 Earth, then there are barely seven billion entities in this system. The logic of the idea defeats itself.
Conclusion
I am quite certain I will draw significant ire for writing this piece. Not because I "refuted" the energy equation, as it was contentious from the start, and rather disliked in the nerd circles with a liking for precision and fine detail, which are the same reasons why those same nerds load the hax0ring attempts shown in the sequel as reasonably realistic. No, I will be mocked because I don't consider The Matrix to be as fun ans cool as I thought it was 25 years ago. But hey.
Anyway, using humans as fuels is a pretty lousy idea. Not only do you need lots of energy to sustain human life, the output is meaningless. The "engine" has low efficiency, and there are superior alternatives. And we didn't even discuss nuclear fusion, which I presume would be a thing around the time of The Matrix future. So really, there's no value in it, except maybe shock value. Then again, sleeping cozily in a spotless simulation, going to work, hobbies, pre-Internet fun, music on CDs. Man, Cypher was right, you know. Hi hi. Take care.
Cheers.